Air Conditioner Maintenance

We all need Air Conditioners in our cars, but there is a negative side to this too. CFC based refrigerant causes terrible damage to the ozone layer. Our mechanics will have to make sure that there are no leaks, and fix them if there are, before they can add any R-12 to our air conditioning systems. Naturally, this cost will be passed along to us. Recovered refrigerant will be recycled. Capturing refrigerants and restoring them for reuse is not only environmentally sound, but mechanically safe. Each molecule of CFC in the atmosphere has a 120 year life that will destroy tens of thousands of ozone molecules. This means that a CFC molecule released in 1991 will still be damaging the ozone layer in 2100.

Air Ducts

The air ducts control the passage of hot or cold air into the interior of the car. They are operated by a control on the dash, either manually or automatically.

Air Pump

The air pump pumps compressed air into the exhaust manifold and in a few cases to the catalytic converter. The oxygen in the pressurized air helps to burn quite a bit of any unburned hydrocarbons (fuel) and thereby converts the poisonous carbon monoxide into good old carbon dioxide. A belt from the engine drives the air pump. It has little vanes (thin, flat, curved fins) that draw the air into the compression chamber. Here, the air is compressed and sent off to the exhaust manifold where it speeds up the emissions burning process. Stainless steel nozzles are used to shoot the air into the exhaust manifold, because they will not burn. Some engines use a pulse air injection system. Pulses of exhaust gases are used by the system to operate an air pump that delivers air into the exhaust system.

Alternator or Generator

The chief source of power of the electrical system is the alternating-current generator, or alternator. Its shaft is driven by the same belt that spins the fan and it keeps the engine running. It converts mechanical energy into alternating-current electricity, which is then channeled through diodes that alter it to direct current for the electrical system and for recharging the battery.

Ammeter

The device is used to determine whether the electrical system is charging, discharging, or staying “level”. The gauge should dip when the engine is started, then go up as the alternator re- charges the battery. After a few minutes, it should go to its middle position.

Automatic Transmissions

Automatic transmission has made driving a lot easier to drive and than manual transmission. The best part is that you don’t have to use a clutch pedal or gearshift lever. An automatic transmission manages all of this on its own. Automatic transmissions automatically change to higher and lower gears with changes in the car’s speed and the load on the engine. These transmissions are also aware of how far down you have pushed the gas pedal, and shift accordingly.

The output shaft turns the governor. The rolling of the governor is directly proportional to the speed of the car. The centrifugal force from the governor sends the oil is sent from the pump to the shift valves. The shift valves then move out sending the transmission fluid to the gear shifting mechanisms in the transmission. When the car slows down, the valves move in and send the transmission fluid in the opposite direction, thus changing the gears. The different gears are selected by routing the pressure to the clutches and brake bands.

Ball Bearings

A ball bearing is an antifriction bearing consisting of a hardened inner and outer race with a series of hardened steel balls separating the two. “Sealed” bearings have plastic dust seals and are greased only at the time of manufacture.

Battery

The battery is the vehicle’s initial source of energy used to start the engine. The battery is then taken over the alternator to supply the car’s electrical needs and to restore energy to the battery. A 12-volt storage battery consists of layers of positively and negatively charged lead plates that, together with their insulated separators, make up each of six two-volt cells. The fluid in the cells are electricity-conducting liquid (electrolyte) that is usually two-thirds distilled water and one-third sulfuric acid. Spaces between the immersed plates provide the most exposure to the electrolyte. The interaction of the plates and the electrolyte produces chemical energy that becomes electricity when a circuit is formed between the negative and positive battery terminals

Battery Charging Methods

As the battery charging methods vary, take into consideration the following, (1) electrical capacity of the battery being serviced; (2) temperature of electrolyte; (3) battery state of charge at start of charging period; and (4) the age and condition of the battery. Follow step by step instructions on the manufacturer’s battery charger guide, or ideally, use an automatic battery charger that senses battery voltage and automatically shuts off – or almost shuts off – when the battery reaches or approaches the fully charged state.

Battery Cables

These are used to connect the battery to the rest of the starting and charging circuits. The battery cables must be of sufficient size to carry such heavy current as a starting motor will draw about 200 amps of current. The cables are prone to corroding as they are close to the battery and therefore it is important that the cables make good electrical contact with the cable clamps. Similarly, clamps must make good electrical contact with the battery posts. Any looseness or corrosion could result in high resistance and consequent voltage drop.

Battery Terminals

The points which connect the wires are called the battery points. The “post” type terminals are being phased out by the “side-mount” type of terminals which use a bolt to screw into the side of the battery and clamp on the battery wire. The vapors from battery acid causes corrosion to form on the lead surfaces, which makes it necessary to clean these periodically. Be sure to wash your hands thoroughly as the corrosion on the terminals is acidic!

Body

The body shell is a fairly complex assortment of large steel sections. These sections have been stamped into specific shapes that make up the body of your car. These parts are designed to do many jobs at once; protect the occupants from the elements and in collisions, provide solid mounts for all other systems, and to slice through the air with minimal resistance. The body also has one other job which is usually important to the owner… it has to look good! Although the zillions of parts that make up a car are all very important, it is also important that the car’s body be able to make riding in a car bearable for you. The body and the suspension system give us a smooth ride, and cushion us from the jarring of the road. Improvements in the body of the car are carried out so that it should go forward with as little up-and-down, and side-to-side movement as possible.

Brake Animation

This animation demonstrates the basics of hydraulic disc and drum brakes in action. As the brake pedal is pressed, the piston in the master cylinder sends pressure (via the brake lines) to the wheel cylinders within the caliper and the drum brake. The pad-to-disc and shoe-to-drum friction stops the vehicle, converting its momentum into heat energy.

Brake Cooling Ducts

Brakes tend to lose their effectiveness if they get hot. Cool air to be directed onto the brakes, increasing braking potential and reducing brake fade. The air dam has a small opening, behind which runs a small tube to the backing plate. This allows cool air to be directed onto the brakes, increasing braking potential and reducing brake fade.

Brake Fluid

Brake fluid is a special liquid used in hydraulic brake systems. It should be impervious to heat, freezing, thickening, and bubbling. There are different types of brake fluids made for different types of systems. These should never mixed. Be sure of what you use in the master cylinder reservouir, because, if the brake fluid gets contaminated, you’d have to change all of the piston seals and hoses. It should be noted that brake fluid is highly corrosive to paint, and care should be used not to get it on your car’s finish.

Brake Pedal

The brake pedal is located on the left side of the accelerator pedal and it slows down or stops the vehicle. The brake shoes and friction pads are forced into contact with the brake drums and rotors to slow the rotation of the wheels. The friction between the tires and the road surface then slows the speed of the vehicle. The pedal is solidly mounted to the firewall, and works as a force-multiplying lever. If the power assist fails, the pedal’s leverage allows you to generate pounds of pressure at each wheel cylinder. A brake pedal should not sink more than an inch or two, no matter how hard it is pressed with the foot. Warning: Any change in this is a cause for serious concern.

Calibrated Friction Brake

A calibrated friction brake is included in the fuel tank unit. This prevents the wave motions of the fuel from fluctuating the pointer on the dash unit, so that the fuel reading will correctly correspond to the amount of fuel available in the tank.

Catalytic Converter

A catalytic converter prevents noxious gases like hydrocarbons, carbon monoxide and nitrogen oxides from polluting the environment by converting them into water vapor and carbon dioxide. The catalytic converter is installed in the exhaust line, between the exhaust manifold and the muffler, and makes use of chemicals that act as a catalyst. The harmful gases enter the catalytic converter, which is a kind of stainless steel container. This is lined with chemicals such as aluminum oxide, platinum and palladium. These chemicals cause the carbon monoxide and hydrocarbons to change into water vapor and carbon dioxide. Some converters have a third lining of chemicals, platinum and rhodium, that reduce nitrogen oxides (three-way, dual bed converter).

Clutch

The clutch allows to connect and disconnect the engine and the transmission while starting up and during shifts. Friction plates route the rotation of the engine crankshaft to the gears, and then to the wheels. It takes the rotation up slowly, so that you aren’t off to a screeching start. In a manual transmission, the clutch is disengaged when you press the pedal down. The pedal works the thrust pad, and it presses levers in the middle of the clutch cover. Doing all this lifts the pressure plate away from the clutch plate. The flywheel (which is turned by the crankshaft from the transmission shaft) gets disconnected. When you lift the clutch pedal, springs force the pressure plate and clutch plate against the flywheel. The clutch plate friction linings allow it to slide before becoming engaged. The sliding causes a smooth start instead of a jolt.

Clutch Pedal, Cables and Levers

One way to activate the throw-out fork of the clutch is by using a system of levers and cables. These levers and cables are connected between the clutch pedal and the throw-out fork. When you press the clutch pedal with your foot, the pressure is transmitted to the fork through the cable and lever arrangement.

Clutch Plate

The clutch plate is a thin, steel, disc whose center is connected to the transmission input shaft by a grooved piece of metal, or hub. The disc is covered with material that is similar to the break linings. This material allows the clutch to slip smoothly and quietly.

Compressor

The job of the compressor is to move liquid refrigerant around in a pipe. The compressor pumps, or forces, the liquid from the evaporator into a condenser and expansion valve, and then back to the evaporator. There are three common types of compressors:

• Two-cylinder reciprocating piston type
• Four cylinder RADIAL type
• Six cylinder AXIAL type

The engine drives the compressor with a belt. In action, the compressor takes the low pressure refrigerant from the evaporator and compresses it according to speed and air temperature. The inlet side is known as the low (pressure) side and the outlet side is known as the high (pressure) side. The compressor compresses the refrigerant, and raises its temperature higher than that of the surrounding air. Then, the compressor forces the refrigerant into the condenser.

Compressor Relay

A capillary tube from a cycling switch lets the switch know what the temperature is in the evaporator. This switch turns the compressor on and off to keep the evaporator temperature at about 32 to 45 degrees F. The relay switch keeps moisture from freezing on the evaporator core.

Condenser

The condenser is a long tube that goes back and forth through a multitude of cooling fins. It is mounted in front of the radiator to take advantage of the forced air provided by the fan and the motion of the car. As the highly pressurized refrigerant (vapor) flows into the condenser, it gives off heat and warms the condenser. This causes the condenser to be hotter than the forced air coming through the condenser. The condenser hands its heat off to the forced air and turns the refrigerant back into cool liquid in the expansion valve, where it heads back to the evaporator

Coolant (Antifreeze)

Coolant (antifreeze) is a complex chemical liquid helps prevent freezing in cold climates, so that cars can operate in sub zero temperatures, and boils at a higher temperature than water. Besides this, it also lubricates the water pump as it flows through. Some antifreeze compounds are specially formulated for aluminum radiators. Keep the coolant somewhere between 20 and 60 percent of the mixture in your car, depending on the car and climactic conditions. Do not use a strong antifreeze mixture as it can cause leaks in your car’s cooling system. Coolant is extremely poisonous and should be handled with care. If it spills on the ground it can kill stray animals that drink it.

Crankshaft

The crankshaft converts the up and down motion of the pistons into a rotary motion. It provides the turning motion for the wheels. It works much like the pedals of a bicycle, converting up-down motion into rotational motion. The crankshaft is usually either alloy steel or cast iron. The crankshaft is connected to the pistons by the connecting-rods. Some parts of the shaft do not move up and down; they rotate in the stationary main bearings. These parts are known as journals. There are usually three journals in a four cylinder engine.

Dash Controls

The dash board, behind the steering wheel displays the control panel of the car. Duplicate fragments of the control panel are found in the interior of your vehicle, such as automatic door locks, extra light switches, etc. Many functions of the car are carried out through the dash board, like turning on the headlights, windshield wipers, horn, turn signals, air conditioning, cassette player, etc. It also contains all of your gauges; gas, temperature, tachometer, etc., which enables the monitoring of the operating conditions of your engine and charging system, fuel level, oil pressure and coolant temperature. It ensures that all the controls are within the drivers reach.

Diesel Fuel Injector

The diesel fuel injector is a pressure valve, but it has specific components that allow it to disperse the diesel fuel in set patterns, depending on the design of the valve. Diesel fuel injectors receive the pressurized impulse from the diesel fuel pump, and allow the fuel to enter the combustion chamber when it is needed. If the diesel fuel injectors get clogged, engine performance suffers.

Diesel Fuel Pump

Diesel fuel pumps inject a specific amount of fuel during a specific time, and control the injectors by the pressure waves of the fuel that they pump. The diesel fuel pump has mechanisms in it, which allows more or less fuel to be pumped. If less fuel is pumped into the cylinders, this slows the engine, and vice versa. It thus also regulates the speed. A series of gears link them to the crankshaft or the camshaft, allowing the fuel pump to be driven directly by the crankshaft of the engine. Some may be belt or chain driven.

Differential

The differential is the thing that works both drive axles at the same time, but lets them rotate at different speeds so that the car can make turns. When a car makes a turn, the outer wheel has to turn faster than the inner wheel, due to the difference in the length of the paths they take. The differential is located between the two wheels, and is attached to each wheel by a half-shaft rotated through a bevel gear. Four-wheel drive cars have a separate differential for each pair of wheels. A grooved, or splined, axle side gear is positioned on the splined end of each axle. The side gears are driven by “spider” gears, which are little gears mounted on a shaft attached to the differential case. As it is supported by the differential case, the side gear can turn inside the case. The differential case can be turned, revolving around the axle gears. The differential pinion (a pinion is a small gear that either drives a larger gear or is driven by one) shaft turns the ring gear, which is fastened to the differential case. The propeller shaft (drive shaft) connects the transmission output shaft to the differential pinion shaft. The turning differential case is mounted on two large bearing holders. These bearings are called carrier bearings. The propeller shaft rotates the ring gear pinion, and the pinion turns the ring gear. The ring gear then turns the differential case and pinion shaft, but the axle side gears will not turn. By passing the differential pinion shaft through two differential pinion gears that mesh with the side gears, the case will turn and the axle side gears will turn with it. During turns, the side gears turn at rates dictated by the radius of the turns, and the spider gears then turn to allow the outer wheel to turn faster than the inner one.

Drive Shaft

The drive shaft, or propeller shaft, connects the transmission output shaft to the differential pinion shaft. Since all roads are not perfectly smooth, and the transmission is fixed, the drive shaft has to be flexible to absorb the shock of bumps in the road. Universal, or “U-joints” allow the drive shaft to flex (and stop it from breaking) when the drive angle changes. There are two types of drive shafts, the Hotchkiss drive and the Torque Tube Drive.

Drive Wheel/Axle

The drive wheel is the end of the axle shaft; it has lugs protruding from it. The lugs are separate pieces that are mounted in the drive wheel. The drive wheel bolts onto the brake drum and the wheel rim of the car itself. It is usually a disc about six or seven inches in diameter. Occasionally the drive wheel and the axle shaft are all one piece.

Dynamic Wheel Balance

“Dynamic” balance is the equal distribution of weight on each side of the vertical centerline of the wheel and tire assembly. Unbalance on either or both sides of a plane of rotation, called dynamic unbalance, causes the wheels to bounce, resulting in flat spots on the tire tread and worn ball joints, tie rod ends, steering gears, and shock absorbers. Dynamic unbalance in the front wheels will cause them to wobble.

EGR Valve

The Exhaust Gas Recirculation (EGR) valve sends some of the exhaust gas back into the cylinders to reduce combustion temperature. This is required because nitrous oxides (nasty pollutants) form when the combustion temperature gets above 2,500 degrees F. This is as a result of the formation of nitrous oxides when the nitrogen in the air mixes with the oxygen. When it’s sunny, the nitrous oxides from the exhaust get together with the hydrocarbons in the air to form smog. This is when the EGR valve comes in handy. By recirculating some of the exhaust gas back through the intake manifold to the cylinders, we can lower the combustion temperature. Lowering the combustion temperature lowers the amount of nitrous oxide produced. Consequently, less of it comes out the tail pipe. There are two types of EGR valves. One operates through the use of a vacuum, and the other operated through the use of pressure. Both types allow the exhaust gas in to lower the combustion temperature when it gets too high.

Electric Fuel Pump

Used previously for heavier vehicles, they have only recently become operational in cars. The replacement types usually use a diaphragm arrangement like the mechanical pumps, except that it is actuated by an electrical solenoid. It uses a small turbine wheel driven by a constant speed electric motor. The entire unit is located in the fuel tank and submerged in the fuel itself. When the engine is running the pump pump operates continuously, thus exerting a constant pressure which supplies the maximum fuel demands of the engine. When less fuel is required, the pump does not deliver at full potential, because the turbine is not a positive displacement type like the mechanical pump. Consequently, the turbine will run without pumping fuel and so, needs no means of varying fuel delivery rate like its mechanical counterpart. Since the fuel can flow past the spinning turbine blades, there is no need for pump inlet and outlet valves nor is there any need to vary its speed. A relay for the electric fuel pump is used to complete the circuit to the fuel pump. This cuts off current to the fuel pump in the event of an accident.

Electronic Fuel Injection

Injectors are opened by solenoids operated by an electronic control unit, as opposed to mechanical injection systms. Since the fuel has no resistance to overcome, other than insignificant friction losses, the pump pressure can be set at very low values, consistent with the limits of obtaining full atomization with the type of injectors used. The control unit, depending on the operating conditions of the engine, determines the amount of fuel to be injected. The conditions depend on manifold pressure, accelerator enrichment, cold-start requirements, idling conditions, outside temperature and barometric pressure. The systems work with constant pressure and with ‘variable timed’ or ‘continuous flow’ injection. The advantages. To begin with, it has fewer moving parts, no need for ultra-precise machining standards and quieter operation. Also, there is less power loss, a low electrical requirement, no need for special pump drives, no critical fuel filtration requirements, no surges or pulsations in the fuel line. More than anything else, it costs lesser than its mechanical counterpart.

Evaporator

The evaporator is a long tube, or coil, that goes back and forth through a multitude of cooling fins. The refrigerant is a liquid when it enters the evaporator. A fan blows warm air over the evaporator and causes the liquid refrigerant to boil. After it has absorbed the heat from the warm air, the warm air isn’t warm anymore. The same blower that blows the warm air (that is now “cool” air) over the evaporator, keeps on blowing it into the interior of your car, and you have — air conditioning! The evaporator also removes the moisture from the air coming through its fins and turns it into water. The water just drains off. The temperature of the evaporator coil can go from 33 degrees F to 0 degrees F. If it goes below 32 degrees F, the moisture that’s supposed to drain off the coils will freeze. This makes for a very (surprise!) inefficient system, so a thermostatic switch is used to connect and disconnect it to the compressor as necessary.

Exhaust Manifold and Header

Usually constructed of cast iron, the exhaust manifold is a pipe that conducts the exhaust gases from the combustion chambers to the exhaust pipe. It has smooth curves in it for improving the flow of exhaust. The exhaust manifold is bolted to the cylinder head, and has entrances for the air that is injected into it. It is usually located under the intake manifold. A header is a different type of manifold; it is made of separate equal-length tubes.

Fan Clutch

The fan clutch is a small fluid coupling with a thermostatic device and controls a variable-speed fan. It ensures that the fan will rotate at just the right speed to keep the engine from overheating, and reduces drive to the fan when it is no longer needed. The fan clutch has a fluid coupling partly filled with silicone oil designed for just that purpose. When the temperature of the air passing through the radiator rises, the heat alerts a bimetal coil spring to “uncoil” or expand. When it expands, it allows just a little more oil to enter the fluid coupling, so the fluid coupling starts to rotate the fan. If the air coming through the radiator is cool, the opposite happens; the coil spring contracts, the oil leaves the fluid coupling and the fan slows. Slowing the fan when it is not needed reduces fuel consumption, makes less noise and saves engine power. Sometimes a flat bimetal strip spring is used instead of a coil spring; it bows out and in when the temperature rises and drops, letting oil in and out of the fluid coupling.

Filler Cap (Brake Fluid Reservoir Cover)

The cap on the brake fluid reservoir has a hole for air, or is vented, to allow the fluid to expand and contract without creating a vacuum or causing pressure. A rubber diaphragm goes up and down with the fluid level’s pressure, and keeps out any dust or moisture.

Flywheel

The large wheel connected to the crankshaft provides the momentum to keep the crankshaft turning without the application of power, through the energy generated during the power stroke. This energy is also used to drive the crankshaft, connecting rods and pistons during the three idle strokes of the 4-stroke cycle. This makes for a smooth engine speed. The flywheel forms one surface of the clutch and is the base for the ring gear.

Frame (Chassis)

The basic structure of the vehicle is the frame and it provides a good anchor point for the suspension system. There are two types of frames; integral frames, or ‘unibody’, and conventional frames. A conventional frame is basically a ‘one-piece’ frame; or two ‘one-piece’ frames fastened together. These frames are extremely rigid to keep all the parts of the car in perfect alignment, which are attached to it. It is constructed of heavy steel and welded or cold riveted together. Cold riveting keeps the rivets from shrinking after they cool off. The integral, or unibody, frame is just the opposite. With this type of frame, the body parts are used to structurally strengthen the entire car, and all of the sections are welded into one piece. Sometimes the parts of the body and the suspension system are attached and reinforced. Also, some unibody frames have partial front and rear frames for attaching the engine and suspension members.

Fuel Pump

The fuel pump has three functions: to deliver enough fuel to supply the requirements of an engine under all operating conditions, to maintain enough pressure in the line between the carburetor and the pump to keep the fuel from boiling, and to prevent vapor lock. Excessive pressure causes the carburetor float needle off its seat its seat resulting in high fuel level in the float chamber, leading to high fuel consumption. Highest pressure occurs at idling speed and the lowest at top speed.

Fuel Tank

The fuel tank stores the excess fuel until it is needed for operation of the vehicle. The fuel tank has an inlet pipe and an outlet pipe. The outlet pipe has a fitting for fuel line connection and may be located in the top or in the side of the tank. The lower end is about one-half inch above the bottom of the tank so that collected sediment will not be flushed out into the carburetor. The bottom of the tank contains a drain plug so that tank may be drained and cleaned

Gaskets

Gaskets and seals the secure machined joints, and prevent fluids and gasses (oil, gasoline, coolant, fuel vapor, exhaust, etc.) from leaking. The cylinder head has to keep the water in the cooling system at the same time as it contains the combustion pressure. Gaskets made of steel, copper and asbestos are used between the cylinder head and engine block. Because the engine expands and contracts with heating and cooling, it is easy for joints to leak, so the gaskets have to be soft and “springy” enough to adapt to expansion and contraction. They also have to make up for any irregularities in the connecting parts

Headlights

Headlights are mounted on the front of the car to light the road ahead during night or foggy days. They have reflectors and special lenses and are usually the sealed beam construction type, with the filament, reflector and lens fused together into an airtight unit. The most popular type of headlight is the halogen type, because it provides bright illumination. The halogen bulb is filled with pressurized gas (halogen) and can produce flying fragments if shattered. Wear protective glasses for changing a halogen lamp and always throw out the old one in the protective carton that comes with the new one.

Heat Exchanger

The “heat exchanger” is a device that uses exhaust heat to aid in fuel evaporation. It usually is built into the intake manifold as an area where the hot exhaust gasses and fuel-air mixture come close to each other.

Heater Core

The heater core is a smaller version of the radiator that is used to keep your toes warm when it’s cold outside. It is mounted under the dashboard. Some of the hot coolant is routed through this little radiator, by more hoses. A small electric fan is also mounted there especially for the purpose of directing the heat inside the car. The principle is exactly the same as the one used in the radiator for your engine, except that the heat is released inside the car instead of outside.

Hood

The car’s hood consists of an inner and an outer panel. The inner panel provides strength, while the outer panel is just a metal cover. The underside of the hood is often covered with a sound-absorbing material. Some high performance cars have ‘hood scoops’ which channel outside air directly to the air filter, which gives improved performance and efficiency. The hood release is a small lever, which is usually mounted under the dash. It is connected to the hood latch by a cable. The hood latch has a safety feature, which requires a second latch to be released before the hood will open. This is to prevent accidental opening while driving.

Ignition Circuit

An ignition circuit is made up of two sub-circuits: the primary, which carries low voltage; and the secondary, which carries high voltage. The primary circuit is controlled by the ignition key. It releases 12 volts of electricity from the battery or alternator through the coil to a set of breaker points in the lower part of the distributor, or to the relay in electronic ignition applications. When the points or relay are closed, current flows through the chassis back to the battery, completing the circuit. When the points or relay are open, the flow stops, causing a high-voltage surge to pass from the coil through a rotor in the top of the distributor to the spark plugs. Once the car has started, the voltage regulator protects the battery from being overcharged by the alternator. part of the low -voltage current is absorbed by the condenser when the points are open.

Idler Gears

These are small gears which are not directly linked to anything. Idle gears are used to reduce or increase rotation speeds, and reverse directions of rotation. The center gear would be considered an idle gear, if three gears are connected in a string.

Indicator Needle

This is the pointer on your gauge that shows you the gauge’s current reading. Its examples are those found in your speedometer, temperature gauge, tachometer and oil pressure gauge.

Intake Stroke

The first stroke is called the intake stroke. The piston moves down the cylinder, creating a partial vacuum in the cylinder. A mixture of air and fuel is then forced through the inlet valve into the cylinder by atmospheric pressure, now greater than the pressure in the cylinder. The exhaust valve stays closed during the stroke.

Knock Sensor

The knock sensor senses when fuel is burning unevenly and causing “knocking” or irregular vibrations in the engine. It consists of an electric coil that is wound around two ceramic rods with a magnet in the center. The vibration of the engine causes the rods to vibrate. This disturbs the coil’s magnetic field and alters the current passing through the coil. This disturbance returns to the computer as a signal pattern that the computer analyzes. The computer then determines whether the vibrations are characteristic of engine knocking.

Lever Return Spring

A return spring, or restoring spring, is a coil spring that moves something, such as a valve or diaphragm back to its normal position and holds it there.

Lighting Circuit

The automobile lighting circuit includes the wiring harness, all the lights, and the various switches that control their use. The complete circuit of the modern passenger car can be broken down into individual circuits, each having one or more lights and switches. In each separate circuit, the lights are connected in parallel, and the controlling switch is in series between the group of lights and the fuse box. The parking lights, are connected in parallel and controlled by a single switch. In some installations, one switch controls the connection to the fuse box, while a selector switch determines which of two circuits is energized. The headlights, with their upper and lower beams, are an example of this type of switch. Again, in some cases, such as the courtesy lights, several switches may be connected in parallel so that any switch may be used to turn on the lights.

Lifter Body

The valve lifter body houses the valve lifter mechanism. The valve lifter is the unit that makes contact with the valve stem and the camshaft. It rides on the camshaft. When the cam lobes push it upwards, it opens the valve.

Limiting Coil and Operating Coil

The limiting coil passes the current from the battery to the common connection of two coils at the lower terminal on the dash unit. This current may pass from either the operating coil of the dash unit and the other over to the tank sending unit. When the fuel tank is low or empty, the sliding brush cuts out all resistance in the tank unit. Then the current will passes through the tank unit circuit because of the low resistance, and only a small portion will pass through the operating coil to the dash unit. This coil is not magnetized enough to move the dash unit pointer, which is then held at the “Empty” position by the limiting coil.

When the tank is full or partly full, the float of the tank unit will rise to the surface of the fuel and move the sliding brush over the rheostat, putting resistance in the tank unit circuit. This results in more current will then passing through the operating coil to give a magnetic pull on the pointer, which overcomes some of the pull of the limiting coil. When the tank is full, the tank unit circuit contains the maximum resistance to the flow of the current. The operating coil will then receive its maximum current and exert pull of the pointer to give a “Full” reading. As the tank empties, the operating coil loses some of its magnetic pull and the limiting coil will still have about the same pull so that the pointer is pulled toward the lower reading.

Main Bearings

The main bearing secure the crankshaft in its place. The largest number of main bearings a crankshaft can have is one more than the number of cylinders, but it can have one less bearing than the number of cylinders. Not only do the bearings support the crankshaft, but one bearing must control the forward-backward movement of the crankshaft. This bearing rubs against a ground surface of the main journal, and is called the “thrust bearing.”

Manifold to Exhaust Pipe Gaskets

There are several types of gaskets that connect the exhaust pipe to the manifold. One is a flat surface gasket. Another type uses a ball and socket with springs to maintain pressure. This type allows some flexibility without breakage of the seal or the manifold. A third type is the full ball connector type, which also allows a little flexibility.

Muffler

The muffler serves to muffle the noise coming out of the engine. Exhaust gases leave the engine under extremely high pressure. If these gases escaped directly from the engine the noise would be tremendous. Therefore, the exhaust manifold sends the gases to a muffler where they go through metal plates, or tubes, with a series of holes. The pressure of the gases is reduced when they pass through the muffler, so they go out of the tail pipe quietly. Made of metal, the muffler is located underneath the body of the car. It is connected between the tail pipe and the catalytic converter. There are two types of muffler designs. While one type uses several baffled chambers to reduce noise, the other sends the gases straight through perforated pipe wrapped in metal or fiberglass. This type of muffler is designed for the purpose of reducing backpressure and, consequently, makes slightly more noise.

Nuts and Bolts

Nuts are hexagon shaped metal objects with a threaded hole through them so that they can be attached to bolts. Bolts are cylindrical objects with groves on the outside, which enable them to be screwed into nuts. A bolt without an end is classified as a ‘lug’ or ‘stud’. There are many grades of nuts and bolts. Grades depend on the quality of the materials and the tolerances observed during the manufacture of the nuts and bolts. Nuts and bolts are often separated by washers. Washers have many shapes and sizes. They give the nut and the bolt a firm hardened surface for bedding against. The parts that you put together with nuts and bolts are usually not as strong as the nuts and bolts themselves. The washers allow the nuts and bolts to be fully tightened down, providing a wider area to spread out the force of the tightening and they keep the nuts and bolts from digging into the material when they are tightened.

Oil Filler Cap

The oil filler cap is a plastic or metal cap that covers an opening into the valve cover. It allows you to add oil when the dipstick indicates that you need it. Some cars have the crankcase vented through the filler cap. Oil which is added through the filler passes down through openings in the head into the oil sump at the bottom of the engine.

Oil Gauge

The Oil Gauge lets you know the pressure in the oil pump; and is a direct indicator of the condition of your engine. If the oil gauge gives very low readings, it means that your oil pressure has dropped. The engine would soon grind to a halt if the oil is not forced into the nooks and crannies that need to be oiled.

Overhead Valve (OHV)

In an overhead valve (OHV) engine, the valves are mounted in the cylinder head, above the combustion chamber. Usually this type of engine has the camshaft mounted in the cylinder block, and the valves are opened and closed by push rods.

Parking Brake

The parking brake holds one or more brakes continuously in the applied position. The parking brake employs the regular drum brakes on the rear wheel. Instead of hydraulic pressure, however, a simple mechanical linkage is used to engage the brake shoes. When the parking-brake pedal is depressed (or, in some cars, a hand lever is raised), a steel cable pulls taut a tension lever; other cables draw the brake shoes firmly against the drums. The release knob slackens the cables and disengages the brake shoes. The parking brake is self adjusting. An automatic adjuster in the piston moves on the thrust screw to compensate for lining wear.

Piston, Rings, and Wrist Pin

The piston converts the potential energy of the fuel into the kinetic energy that turns the crankshaft. The piston is a cylindrical shaped hollow part that moves up and down inside the engine’s cylinder. It has grooves around its perimeter near the top where rings are placed. The piston fits snugly in the cylinder. The piston rings are used to ensure a snug “air tight” fit. The wrist pin connects the piston to the connecting rod. Pistons are made of aluminum, because it is light and a good heat conductor. The piston head or “crown” is the top surface against which the explosive force is exerted. It may be flat, concave, convex or any one of a great variety of shapes to promote turbulence or help control combustion. In some, a narrow groove is cut into the piston above the top ring to serve as a “heat dam” to reduce the amount of heat reaching the top ring.

Power Brakes

Power brake are of four general types: vacuum suspended; air suspended; hydraulic booster, and electro-hydraulic booster. Most power brakes use vacuum suspended units, which contain a large vacuum-powered booster device to provide the added thrust to the typical power-brake. Pressure on the brake pedal pushes forward a rod connected to the pistons of the two master cylinders. The pistons begin forcing fluid into the front and rear brake lines. At the same time, the brake-pedal pushrod positions the vacuum-control valve so that it closes the vacuum port and seals off the forward half of the booster unit. The engine vacuum line then draws off the air, creating a low-pressure vacuum chamber. Atmospheric pressure in the control chamber then pushes against the diaphragm, dividing the two chambers. The pressure on the diaphragm, which is locked to the pushrod, forces it forward, supplying even more pressure on the pistons. The safe driver is always ready to apply the total force needed to stop their vehicle, even if the engine quits (removing the power assist).

Push Rod

A push rod is a connecting link in an operating mechanism. Two examples are the rod between the valve lifter and rocker arm on an overhead valve engine, and push rods at the piston ends which apply pressure to the brake shoes.

Rear View Mirror

The rear view mirror is a wide rectangular mirror that you (the driver) use to view anything behind the car. You don’t have to take your eyes off the road to turn your head around. On most cars, the rear view mirror has a “day/night” selection switch that tilts the mirror inside its glass housing without tilting the exterior glass housing itself. The switch tilts the mirror upward, about five degrees, to divert the majority of the light striking the mirror up on to the headliner of the car. The light that you see when the mirror is on the “night” setting is actually bouncing off the glass housing (a good reason to keep it clean). The percentage of light reflected into your eyes in the night position, is very small compared to the amount that would normally be reflected into your eyes in its normal position.

Radial Tyres

In radials tyres the ply or ply cords are alligned at 90 degrees to the circumference. While radials improve performance the fact is that they are not very good for bad roads and overloading. The suspension of a vehicle has, also, to be modified to accept radials. Radials offer much better grip of the road especially on surfaces which offer poor wheel traction like wet of slippery roads.

Radiator

The radiator is used to dissipate the heat that the coolant has absorbed from the engine. It is constructed to hold a large amount of water in tubes or passages which provide a large area in contact with the atmosphere. It generally consists of a radiator core, with its water-carrying tubes and large cooling area, which are connected to a receiving tank (end cap) at the top and to a dispensing tank at the bottom. Side flow radiators have their “end caps” on the sides, which allows a lower hood line. While in operation, water is pumped from the engine to the top (receiving) tank, where it spreads over the tops of the tubes. As the water passes down through the tubes, it loses its heat to the airstream, which passes around the outside of the tubes. To help spread the heated water over the top of all the tubes, a baffle plate is often placed in the upper tank, directly under the inlet hose from the engine. Sooner or later, almost everyone has to deal with an overheating car. Since water is readily available, it is not beyond the ability of most people to add some to their radiator if it’s low.

Radiator Cap (Pressure Cap)

The radiator cap is more than a cap for your radiator; it keeps your engine cool by sealing and pressurizing the coolant inside it. It is designed to hold the coolant in the radiator under a predetermined amount of pressure. If it was not kept under pressure, it would begin to boil, and soon all the coolant would have boiled away. However, the radiator (or pressure) cap prevents this from happening by exerting enough pressure to keep the coolant from boiling. If your cooling system is under too much pressure, it can “blow its top”! To prevent this, the radiator cap has a pressure relief valve. The valve has a preset rating that allows it to take just up to a certain amount of pressure. When you turn the cap on the filler neck of the radiator, you seal the upper and lower sealing surfaces of the filler neck. The pressure relief valve spring is compressed against the lower seal when you lock the cap. The radiator filler neck has an overflow tube right between the two sealing surfaces. If the pressure in the cooling system exceeds the preset rating of your cap, its pressure relief valve allows the lower seal to be lifted from its seat. Then the excess pressure (coolant, air) can squish through the overflow tube to the ground or the coolant reservoir. Once enough pressure has been released (the caps preset rating), the pressure relief valve is again closed by the spring. The pressure cap can be tested with a cooling system pressure tester, using an adapter, to make certain that it is living up to its pressure rating. It should be replaced if it fails the test. It should be noted that most radiator pressure caps are not meant to be removed, and that the coolant should always be added through the expansion (overflow) tank. If you happen to remove the radiator cap from a hot engine, the pressure can cause steam to shoot out and seriously burn you.

Radiator Grille

The radiator grille is the part of the body shell on the front of your car that covers the area where the air enters. The radiator grille can also be part of the bumper on some cars. The radiator is connected to the shroud for the radiator, which directs the air that comes in through the radiator grille to the radiator only. This prevents the air from escaping around the radiator and failing to cool the engine. On newer cars, the radiator grille has been lowered to take advantage of lower hood lines, brought about by an effort to increase fuel efficiency. Older cars had massive grilles, whereas the cars now produced have smaller more aerodynamic grilles.

Radiator Shroud

The radiator shroud prevents the recirculation of air around the fan. It is usually a plastic hood that encloses the fan to guide the air through the core, and stop it from coming back around and through the fan again. It also protects you from the fan blades!

Rear End Tunnel

The rear end tunnel provides clearance for the drive shaft and the housing of the differential. It allows the rear end to travel up and down with suspension motion; it clears the differential housing by a maximum of three or four inches when the suspension is fully compressed. Often forming the front of the trunk floor, it is attached to the wheel wells on each side as well as the floor pan and the trunk floor.

Reverse-flow Muffler

The reverse-flow has multiple pipes, and is used to lessen the noise made from an automobile. Four chambers and a double jacket are used to accomplish muffling of the exhaust noise. Exhaust gases are directed to the third chamber, forced forward to the first chamber, from where they travel the length of the muffler and are exhausted into the tail pipe.

Ring Gear

The ring gear is connected to the differential case. A ring gear attached to a pinion gear and shaft turns the differential case. The propeller shaft connects the transmission output shaft to the differential pinion shaft. It is connected to the ring gear pinion shaft.

Roller Bearings

They are used in wheel bearing applications. They consist of

1. An inner “race” which is a hardened ring that is slightly tapered on the outside and
2. An outer race, a hardened ring that is slightly tapered on the inside and
3. A set of rollers contained in a cage. These bearings must not be crushed together, (the angle of assembly drives them together) creating friction if they are tightened too far. Roller bearings need to be repacked periodically with fresh grease to insure a long life.

Rotary Engine

The rotary engine applies power directly to the transmission. Its construction allows it to provide the power of a conventional engine that is twice its size and weight and that has twice as many parts. A large combustion chamber in the form of a pinched oval, called an epitrochoid is the basic unit of the rotary engine. Within this chamber all four functions of a piston take place simultaneously in the three pockets that are formed between the rotor and the chamber wall. Just as the addition of cylinders increases the horsepower of a piston-powered engine, so the addition of combustion chambers increases the power of a rotary engine. Larger cars may eventually use rotaries with three or four rotors.

Rotary Valve

The “rotary valve” is the key to the operation of power steering. It directs the power steering fluid under pressure to either side of the rack piston, which converts hydraulic power to mechanical force. Friction from the wheel causes a torsion bar in the rotary valve to deflect. This changes the position of the valve spool and sleeve, directing fluid under pressure to the proper end of the power cylinder. The difference in pressure on either side of the piston (which is attached to the rack) helps move the rack to reduce turning effort

Seat Belts and Air Bags

Air bags protected occupants in ways that seat belts alone cannot. The air bag spreads out the violent impact of a crash and kept occupants from smashing against the steering wheel, dashboard or windshield. Having an air bag and wearing an effective seat belt is the best protection. By this, you are protected from frontal crashes by the air bag — you are also protected by the seat belt in all other types of crashes. With an “effective” safety belt, your body will stop, in a crash, before you hit or go through the windshield and parts of your car. Seat belts are especially important in small cars, because your chances of being killed or badly hurt in a collision with a big car is eight times greater. Wearing your belt will greatly improve your chances of survival. Air bags can reduce the risk of death in a head-on collision by 26%% and in all serious accidents by 13%.

WITHOUT A BELT, AIR BAGS ARE OF SLIGHT BENEFIT

Air bags are only useful in frontal crashes, so it is not a good idea to skip your seat belt because you have an air bag. Air bags provide very effective protection in frontal crashes, inflating instantly to protect the driver or passenger that has an air bag. They spread the impact of the crash over the individual’s head and chest and protect fragile body parts from the car’s hard surfaces. Many basic improvements have been introduced into cars in recent years. These include anti-burst door latches, safety glass, energy-absorbing steering wheels and columns, head restraints and various seat belt systems. The benefits of the three-point seat belts have been firmly established: over 50%% of fatal and serious injuries to car occupants would be avoided if all occupants wore their seat belts.

Seats

There are basically two types of seats; bench seats or bucket seats. A bucket seat is a low, separate seat for one person. Although we think of them as relatively new, it is interesting to note that in 1905 Henry Ford’s first model had bucket seats. Bench seats are a continuous cushion and backrest across the width of the car (although some vans might have them running along the length of the van). Bucket seats are single units with a separation between the left and right seats. Usually vinyl leather and fabric are used for upholstery.

“Flatsprings” are used for comfort, which are pieces of wire bent into a zigzag pattern. Both ends of the wire are attached to the seat frame, with additional lengths added every six inches. Foam padding is used to cover the flatsprings. The front seats ride on rails that are bolted to the floor. This arrangement allows the seats to move backwards and forwards to suit the driver or passenger. The seat adjustment lever is attached to a latch that fits into teeth along the rail. Moving the lever releases the seat, and allows the seat to move. At any point of the seat’s movement, releasing the lever engages the latch with one of the teeth. Usually there is also a pull-spring; this draws the seat forward when the latch is released. The rear seat usually doesn’t move, because it is secured to the floor of the car. It’s backrest is attached to the partition between the passenger compartment and trunk.

Secondary Brake Shoe

The Secondary brake shoe is the shoe in a set that is energized by the primary shoe. A brake shoe is a carrier to which the brake lining is attached, used to force the lining in contact with the brake drum or rotor. When brakes are applied, the brake shoes or friction pads are forced into contact with the brake drums or rotors to slow the rotation of the wheels. The vehicle slows down as a result of the friction between the tires and the road surface.

Shock Absorber Struts

A strut is a structural piece designed to resist pressure in the direction of its length. On typical “McPherson Strut” use, the shock absorber is built into the strut. Most shock absorber struts are hydraulic units. Like the hydraulic shock struts, faulty units must be replaced as an assembly. Another similar front suspension system is called the “hydraulic shock strut.” This strut serves as a shock absorber and replaces the upper control arm. The coil spring, however, is located between the lower control arm and the body structure instead of being mounted directly on the strut.

Shock Absorbers

The operating principle of direct-acting hydraulic shock absorbers is in forcing fluid through restricting openings in the valves. This restricted flow serves to slow down and control rapid movement in the car springs as they react to road irregularities. Usually, fluid flow through the pistons is controlled by spring-loaded valves and the hydraulic shock absorber automatically adapts to the severity of the shock. If the axle moves slowly, resistance to the flow of fluid will be light. If it is rapid or violent, the resistance is stronger, since more time is required to force fluid through the openings. By these actions and reactions, the shock absorbers permit a soft ride over small bumps and provide firm control over spring action for cushioning large bumps. The double-acting units must be effective in both directions because spring rebound can be almost as violent as the original action that compressed the shock absorber.

Side Beam

The operating principle of direct-acting hydraulic shock absorbers is in forcing fluid through restricting openings in the valves. This restricted flow serves to slow down and control rapid movement in the car springs as they react to road irregularities. Usually, fluid flow through the pistons is controlled by spring-loaded valves and the hydraulic shock absorber automatically adapts to the severity of the shock. If the axle moves slowly, resistance to the flow of fluid will be light. If it is rapid or violent, the resistance is stronger, since more time is required to force fluid through the openings. By these actions and reactions, the shock absorbers permit a soft ride over small bumps and provide firm control over spring action for cushioning large bumps. The double-acting units must be effective in both directions because spring rebound can be almost as violent as the original action that compressed the shock absorber.

Solar Cells

Some electric cars are equipped with solar cells located on the roof of the car, similar to a sunroof. These collect sunlight and convert it into energy. The solar cell is used to augment the existing recharging system.

Spark Plug

A spark plug is a device that is inserted into the combustion chamber of an engine, which contains a side electrode and insulated center electrode. These are spaced to provide a gap for firing an electrical spark to ignite air-fuel mixtures. The high-voltage burst from the coil via the distributor is received at the spark plug’s terminal and conducted down a center electrode protected by a porcelain insulator. At the bottom of the plug, which projects into the cylinder, the voltage must be powerful enough to jump a gap between the center and side electrodes through a thick atmosphere of fuel mixture. Fuel is ignited in the cylinder when the spark bridges the gap.

Spark Plug Wires

The spark plug wire carries 20,000 or more volts from the distributor cap to the spark plug. Spark plug wires are made of various layers of materials. The fiber core, inside the spark plug wire carries the high voltage. Some spark plug wires have a locking connection at the distributor cap. The distributor cap must first be removed and the terminals squeezed together, and then the spark plug wire can be removed from the distributor cap. To work effectively in modern ignition systems, it is important that the resistor ignition cable is capable of producing a specifically designed resistance.

Speedometer Cable

The speedometer cable is connected either to the gearbox output shaft, transmission shaft, or differential. Speed and record mileage is measured by the rotation of these shafts. This information is sent back through the cable where it is recorded on the speedometer. The speedometer and odometer are driven by a cable housed in a flexible casing, which is connected to a gear in the transmission. Speedometer cables break as the result of age, lack of lubrication, or because the cable casing has sharp bends. It may also break from too much friction in the speedometer head.

Speedometer and Odometer

The analog speedometer that is used on cars indicates its speed and records the distance the car has traveled. A speedometer is driven by a flexible cable connected to the speedometer pinion in the transmission. Speedometers are calibrated in miles per hour and/or in kilometers. The instrument records the distance traveled in miles or kilometers. That portion of the instrument is known as the odometer. Most odometers record the total distance traveled. Some also record the distance of individual trips.

Spoiler

A spoiler is a kind of wing that is mounted on the rear of the car in a horizontal position. Its function is to provide high-speed stability. In most cars, the spoiler is purely cosmetic, as a car has to be going over 100 mph to take advantage of the aerodynamics of the spoiler. Some mini-vans also make use of a spoiler, but it’s upside down, and angled. This type of a rear spoiler only keeps the rain off the rear window.

Springs

There are two kinds of springs, leaf springs and coil springs. Springs have life spans that are determined by the number of cycles they can withstand over a certain period of time. If a spring breaks while a car is being driven, the car will suddenly lurch downward. The bottom of the car might be damaged, or you might lose your muffler! Leaf springs are made of individual springs, or plates. If you break one plate of your leaf spring, it won’t be noticeable, but your car might begin to lean to one side or the other. Coil springs, if they break, will suddenly drop the front or rear end of your car and impair driving under the normal conditions of full suspension travel.

Starter

The starter converts electricity to mechanical energy in two stages. Turning on the ignition switch releases a small amount of power from the battery to the solenoid above the starter. This creates a magnetic field that pulls the solenoid plunger forward, forcing the attached shift yoke to move the starter drive so that its pinion gear meshes with the engine’s crankshaft flywheel. When the plunger completes its travels, it strikes a contact that permits a greater amount of current to flow from the battery to the starter motor. The motor then spins the drive and turns the meshed gears to provide power to the crankshaft, which prepares each cylinder for ignition. After the engine starts, the ignition key is released to break the starting circuit. The solenoid’s magnetic field collapses and the return spring pulls the plunger back, automatically shutting off the starter motor and disengaging the starter drive. When the starter is not in use, the drive unit is retracted so that its pinion is disengaged from the flywheel. As soon as the starter is activated, the forward movement of the solenoid plunger causes the shift yoke to move the drive in the opposite direction and engage the pinion and flywheel. The pinion is locked to its shaft by a clutch that unlocks if the engine starts up and the flywheel begins turning the pinion faster than its normal speed. By allowing the pinion to spin freely for a moment, the clutch protects the motor from damage until the drive is retracted.

Starter Circuit

The starter circuit is activated when the ignition switch is turned on, thereby opening a second switch in the solenoid, permitting a second flow of electricity from the battery to the starter motor. The engine cranking circuit is made up of a battery, starting motor, ignition switch, and electrical wiring. On placing the ignition switch in the “start” position, the solenoid windings are energized and the resulting shift lever movement causes the drive pinion gear to engage the flywheel ring gear, and cranking takes place. When the engine starts, an overrunning clutch (part of the drive assembly) protects the armature from too much speed until the switch is opened. At this time, a return spring causes the pinion gear to disengage from the flywheel.

Steering Arms

The steering arms pick up motion from the relay rods and the tie rods, causing the steering knuckles to turn the wheels. They are not used in rack-and-pinion setups.

Steering Systems

The manual steering system incorporates:
1. steering wheel and column,
2. a manual gearbox and pitman arm or a rack and pinion assembly,
3. linkages; steering knuckles and ball joints; and
the wheel spindle assemblies. Power steering systems add a hydraulic pump; fluid reservoir; hoses; lines; and either a power assist unit mounted on, or integral with, a power steering gear assembly. There are several different manual steering gears in current use. The “rack and pinion” type is the choice of most manufacturers.

Stoplight Switch

To signal a stop, a brake pedal operated “stoplight switch” is provided that operates the vehicle’s stop lamps. In addition to lighting the conventional rear lights, the switch also operates the center high-mounted stop lamp, which became mandatory on later models. Cruise control equipped vehicles may also utilize a vacuum release valve. In this case, movement of the brake pedal actuates both the vacuum release valve and the stoplight switch.

Sway Bar

Some cars require stabilizers to steady the chassis against front-end roll and sway on turns. Stabilizers control this centrifugal tendency that forces a rising action on the side toward the inside of the turn. When the car turns and begins to lean over, the sway bar uses the upward force on the outer wheel to lift on the inner wheel, thus keeping the car more level.

Thrust Bearings

Thrust bearings are similar to ball bearings except that the plates that the balls ride between are designed as flat washers. The balls riding between these washers reduce side-to-side load. These are used inside of the transmission, rear end and many other areas of the car.

Tie Rod Ends

Tie rod ends are utilized in the steering linkage, steering knuckle pivot supports, and various other hinge mechanisms. Ball joints that join the key parts of the steering linkage pass on the steering wheel’s motion no matter what the angle of the linkage or the vibration from the road.

Timing Chain/ Belt

The automobile engine uses a metal timing chain, or a flexible toothed timing belt to rotate the camshaft. The timing chain/belt is driven by the crankshaft. The timing chain, or timing belt is used to “time” the opening and closing of the valves. The camshaft rotates once for every two rotations of the crankshaft.

Torsion Bars

Torsion bar suspension uses the flexibility of a steel bar or tube, twisting lengthwise to provide spring action. Two rods of spring steel are used in this type of suspension. One end of the bar is fixed solidly to a part of the frame behind the wheel; the other is attached to the lower control arm. As the arm rises and falls with wheel movement, the bar twists and absorbs more of the road shocks before they can reach the body of the car. Just like a spring that rebounds after it has been compressed, the bar untwists when the pressure is released. Adjusting the torsion bars controls the height of the front end of the vehicle. The adjusting bolts are located at the torsion bar anchors in the front crossmember. The inner ends of the lower control arms are bolted to the crossmember and pivot through a bushing.

Transmission Fluid Dip Stick

The transmission fluid dip stick is a long metal rod that goes into the transmission. It serves check how much transmission fluid is in the transmission. The dip stick is held in a tube; the end of the tube extends into the transmission. It has measurement markings on it. If you pull it out, you can see whether you have enough transmission fluid, or whether you need more by the level of fluid on the markings. Most manual transmissions do not have dipsticks, instead they use a filler hole which is at the same level as the correct oil level. When the oil is topped up or refilled, the mechanic simply adds oil until the filler hole’s level is reached.

Transmission Gears

Most cars have from three to five forward gears, and one reverse gear. The transmission changes the ratio of the engine speed and the wheels by connecting gears in various combinations. First gear connects the engine power to the drive wheels via a pair of reduction gear sets, which gives increased power and reduced wheelspeed when the car is beginning to move. Gears work exactly like levers. A small gear driving a larger one gives an increase in torque, and a decrease in speed, and vise-versa. Transmission gears are heat-treated, high quality steel. They have smooth, hard teeth, cut on precision machinery while red hot. There are many types of gear teeth, but most transmissions use spur and helical gears. Most of the gears are the helical type, because they last longer and are more quiet than spur gears. There has to be enough room (a few thousandths of an inch) between the gear teeth for lubrication, expansion, and any irregularities in size.

Transmission tunnel

The transmission tunnel is a cone-shaped formation in the front of the floor pan. Its shape duplicates the transmission, but it is a little bit bigger and provides about two inches of clearance around the transmission. The transmission tunnel does not exist in front wheel drive cars, because the transmission is on the side of the engine completely under the hood. Only rear-wheel drive cars have transmission tunnels. A manual transmission tunnel has a hole in it to allow the shift linkage to be worked from inside the car. The shifter linkage goes through the transmission tunnel. A rubber boot on the shifter linkage stops dirt, dust and exhaust fumes from entering the passenger compartment. The rubber boot is mounted onto the transmission tunnel and fastened securely around the gearshift linkage. Vehicles with automatic transmission do not need a transmission tunnel because the shift linkage does not usually go through the transmission tunnel. The shift linkage in automatic transmission usually goes in front of the firewall from the base of the steering column.

Tyres

A tyre is a tubular corded carcass covered with rubber or synthetic rubber, which is mounted on a wheel and inflated to provide traction for moving a vehicle and for assisting the brakes in stopping it.

Universal Joint (U-joint)

The Universal joint (U-joint) connects the drive shaft to the transmission output shaft and the differential pinion gear shaft. This joint must be flexible enough to allow changes in the driving angle (road incline) and the drive shaft. This way, the torque is constantly transmitted when the rear axle is moving up and down. Smaller U-joints are used to route the turning motion of the steering wheel through the steering column to the steering box. There are two types of U-joints, the cross and roller type and the ball and trunnion type. The cross and roller type is used the most; it allows the drive shaft to bend. The ball and trunnion type less frequently used; it allows the drive shaft to bend and also permits backward and forward motion of the drive shaft.

Vacuum Hoses and Motors

Vacuum lines are a series of hoses, or tubing, to the intake manifold. These hoses supply vacuum to various components of the engine, such as the emissions control system. Most air conditioning systems have vacuum motors to open and close the doors on the air conditioning ducts. A vacuum motor is just a small diaphragm with connecting rods to activate the valves of the system. They have the advantages of simplicity and quietness.

Vacuum Pump

Most of the fuel pumps have a vacuum booster section that operates the windshield wipers at an almost constant speed. The fuel section then functions in the same way as ordinary fuel pumps. One difference is that the rotation of the camshaft eccentric in the vacuum pump also operates the vacuum booster section by actuating the pump arm, which pushes a link and the bellows diaphragm assembly upward, expelling air in the upper chamber through its exhaust valve out into the intake manifold. On the return stroke of the pump arm, the diaphragm spring moves the bellows diaphragm down, producing a suction in the vacuum chamber. The suction opens the intake valve of the vacuum section and draws air through the inlet pipe from the windshield wipers. When the wipers are not operating, the intake manifold suction (vacuum) holds the diaphragm up against the diaphragm spring pressure so that the diaphragm does not function with every stroke of the pump arm. When the vacuum is greater than the suction produced by the pump, the airflows from the windshield wiper through the inlet valve and vacuum chamber of the pump and out the exhaust valve outlet to the manifold, leaving the vacuum section inoperative. With high suction in the intake manifold, the operation of the wiper will be the same as if the pump were not installed. When the suction is low, as when the engine is accelerated or operating at high speed, the suction of the pump is greater than that in the manifold and the vacuum section operates the wipers at a constant speed.

Valve Cover

The valve cover covers the valve train. The valve train consists of rocker arms, valve springs, push rods, lifters and cam (in an overhead cam engine). The valve cover can be removed to adjust the valves. Oil is pumped up through the pushrods and dispersed underneath the valve cover, which keeps the rocker arms lubricated. Holes are located in various places in the engine head so that the oil recirculates back down to the oil pan. For this reason, the valve cover must be oil-tight; it is often the source of oil leaks. One way to determine if your valve cover is bent is to remove the gasket and put the valve cover back on to the cylinder head. When the valve cover and cylinder head come into contact, the cover should sit flat. If it rocks, it is bent. A symptom of a bent or leaking valve cover is a pinching of the valve cover gasket. This means that the gasket is sealing one area and not sealing another area. This condition produces a leak; oil could be leaking down the side of the engine. Some valve covers are hard to access, because they are covered with other engine parts. Chronic valve cover leakage can sometimes be fixed by using two gaskets glued together instead of using just one.

Valve Lifter

The valve lifter is the unit that makes contact with the valve stem and the camshaft and rides on the camshaft. It opens the valve when the cam lobes push it upwards. The engine oil comes into the lifter body under pressure. It passes through a little opening at the bottom of an inner piston to a cavity underneath the piston. The oil forces the piston upward until it contacts the push rod. When the cam raises the valve lifter, the pressure is placed on the inner piston, which tries to push the oil back through the little opening. It can’t do this, because a small check valve seals the opening. When the cam goes upward, the lifter solidifies and lifts the valve. Then, when the cam goes down, the lifter is pushed down by the push rod. It adjusts automatically to remove clearances.

Valve Ports

Valve ports are openings in the cylinder head. Intake ports let the fuel mixture into the cylinder head, and exhaust ports let the exhaust out.

Valve Seals

The valve seal is a unit that goes over the end of the valve stem. It keeps excess oil from getting between the valve guide and the valve stem.

Valve Springs

The valve springs keep the valves closed tightly against their seats until the cam opens the valve. After the cam turns (releasing pressure), the valve springs close the valves.

Valves

The valve opens and close the valve ports. If the ports were always open, the fuel exploded in the combustion chamber would leave through the ports. The explosion has to be kept in the combustion chamber to push the piston down. The valves are set up to open and close at exactly the right moment. One lets the fuel mixture in and closes. After the fuel explodes and pushes the piston down, the other valve lets the exhaust out.

Visor

The visor is a flat sunshade and is usually movable. It is attached to the interior of the car at the top of the windshield. Visors protect the eyes of the driver and passengers from the sun’s glare.

Voltage Regulator

The voltage regulator controls voltage and current output of the alternator by automatically cutting resistance in or out of the field circuit to keep it in a safe value. Varying the resistance alters the amount of current passing through the field. When the battery becomes fully charged, the resistance is cut into the field circuit and the charging rate is decreased. In electromagnetic regulators, the voltage regulator unit limits voltage output by controlling the amount of current applied to the rotating field. The field relay on these regulators connects the alternator field windings and voltage regulator windings directly to the battery. The conventional cutout relay unit has been eliminated by the diodes in the alternator. The current regulator has also been eliminated by the current-limiting characteristic of the alternator design. Basically, in a transistorized or an electronic regulator, the transistor is switched on and off to control the alternator field current. The frequency of switching depends on the alternator speed and accessory load, with the possibility that the on-off cycle may be repeated as often as 7000 times per second. The transistorized units have a voltage limiter adjustment. The electronic units are factory calibrated and sealed. They are also nonadjustable

Water (Coolant) Jackets

Water Jackets are used in cars to keep them cool. It is a collection of passages within the block and head, which let the coolant circulate around the “hot spots” (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off. The engine block is actually manufactured in one piece with the water jackets cast into the block and cylinder head. At normal operating temperature, the water pump forces the coolant through the head gasket openings and on into the water jackets in the cylinder head. It flows around in there, cooling everything off by absorbing the heat. After doing its thing, the coolant flows through the upper hose to the radiator where it releases the heat. Then, the water pump sends it back down into the engine’s water jackets to continue the cooling process. On the sides of the engine are “freeze” or “expansion” plugs, which are sheet metal plugs pressed into a series of holes in the block, and are designed to hold the pressure of the cooling system. However, they pop out if the coolant in the block ever freezes.

Wheel (Slave) Cylinder

The wheel cylinder, also called the brake cylinder or slave cylinder, is a cylinder in which movable piston(s) convert hydraulic fluid pressure into mechanical force. The piston(s) within the cylinder move the brake shoes or pads against the braking surface of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. The cylinder is usually made up of a single-bore cylinder casting, an internal compression spring, two pistons, two rubber cups or seals, two rubber boots to prevent entry of dirt and water, and a bleeder screw (valve). In drum type brakes, the wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the toe end of each brake shoe. In disc brakes, the wheel cylinder is part of the caliper. As the brake pedal is depressed, it moves pistons within the master cylinder, forcing hydraulic brake fluid through the brake lines and into cylinders at each wheel. The fluid under pressure causes the wheel cylinders’ pistons to move, which forces the shoes or pads against the brake drums or rotors. Two-way pressure is applied when the wheel cylinder is activated. Brake fluid enters the center of the cylinder, forcing the pistons apart. Pushrods at the piston ends then apply equal pressure to the brake shoes. When pressure is released, a return spring pulls the pistons together.

Wheel Lugs

The large bolts that go through the wheel rim and secure it to the wheel hub are known as the wheel lugs. They are pressed into the hub from the inboard side so they cannot pull out when tightened. The lug nuts thread onto the wheel lugs, clamping the wheel rim between the hub and lug nuts. If the wheel lug nuts are not properly tightened your wheel will come off. Over- tightening, conversely, can prevent you from being able to change a flat tire.

Wheel Well

The wheel well is either plastic or metal. Metal wheel wells are usually part of the body shell. Metal wheel wells strengthen the structure of the car because of their shape, and because they are strongly welded to the body shell. Most rear wheel wells are made of metal. Wheel wells are coated with a rock-proof, rubberized coating underneath to prevent the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they hit. The front wheels are often made of plastic. This is because it is harder to mount the engine with the front wheel wells in place. Plastic wheel wells can be removed, and are easier to mount the engine during the manufacturing of the car.

Wheels

Wheels come in many different designs and usually fall into two categories: stamped sheet metal and machine castings. Some wheels are a combination of the two. Generally cast alloy wheels are higher priced, but have greater strength than stamped sheet metal wheels. The most common are the stamped sheet metal wheels because they are less expensive to produce and are adequate for most uses. Some cars have wire wheels, which consist of three basic components; inner rings, outer rings, and a series of spokes, which connect the two. Cast aluminum wheels are very popular, magnesium wheels are also popular. Both are popular because they are lightweight and strong.

Windshield

Most windshields are stationary. They are fixed in place with a weather-strip made of rubber, which has a groove on the inside and a groove on the outside. The inside groove holds the glass; the outside groove holds the metal rim of the windshield opening in place. The glass “floats” in a plastic sealant that is spread out between the edge of the glass and the frame of the windshield. Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it is struck during a collision. The glass sticks to the plastic to eliminate glass from flying around the interior and injuring someone.

Windshield Washers

All cars use an electric pump-operated windshield washer with a positive displacement washer pump. On some, the motor is placed in the washer reservoir, while on others, it is driven by a wiper motor. When the pump is attached to the wiper motor, the four lobe cam starts a spring-loaded follower, but the pump does not operate all the time that the wiper motor is running. This is because the pumping mechanism is locked out and pumping action occurs.

Windshield Wipers

Most cars have an intermittent wiper system, which permits the driver to select a delayed wipe that operates only every few seconds. A representative wiper/washer unit is the wiper assembly, which incorporates a depressed park system that places the wiper blades below the hood line in the parked position. The relay control uses a relay coil, relay armature, and switch assembly. It controls starting and stopping of the wiper through a latching mechanism. An electric washer pump is mounted on the gear box section of the wiper. The wiper unit gear assembly drives it.

Wires and Cables

Wires and cables conduct electricity. Usually, they are made of annealed copper and are used to carry electricity to the various electrical devices and equipment on passenger cars and trucks. Wire and cable sizes are expressed by a gauge number, which indicates the cross-sectional area of the conductor. The larger the diameter of the wire or cable, the smaller the gauge size number. Cables are made of several strands of wire. The cross-sectional area is equal to the circular mil area of a single strand times the number of strands.

Thrust Bearings

Thrust bearings are similar to ball bearings except that the plates that the balls ride between are designed as flat washers. The balls riding between these washers reduce side-to-side load. These are used inside of the transmission, rear end and many other areas of the car.

Tie Rod Ends

Tie rod ends are utilized in the steering linkage, steering knuckle pivot supports, and various other hinge mechanisms. Ball joints that join the key parts of the steering linkage pass on the steering wheel’s motion no matter what the angle of the linkage or the vibration from the road.

Timing Chain/ Belt

The automobile engine uses a metal timing chain, or a flexible toothed timing belt to rotate the camshaft. The timing chain/belt is driven by the crankshaft. The timing chain, or timing belt is used to “time” the opening and closing of the valves. The camshaft rotates once for every two rotations of the crankshaft.

Torsion Bars

Torsion bar suspension uses the flexibility of a steel bar or tube, twisting lengthwise to provide spring action. Two rods of spring steel are used in this type of suspension. One end of the bar is fixed solidly to a part of the frame behind the wheel; the other is attached to the lower control arm. As the arm rises and falls with wheel movement, the bar twists and absorbs more of the road shocks before they can reach the body of the car. Just like a spring that rebounds after it has been compressed, the bar untwists when the pressure is released. Adjusting the torsion bars controls the height of the front end of the vehicle. The adjusting bolts are located at the torsion bar anchors in the front crossmember. The inner ends of the lower control arms are bolted to the crossmember and pivot through a bushing.

Transmission Fluid Dip Stick

The transmission fluid dip stick is a long metal rod that goes into the transmission. It serves check how much transmission fluid is in the transmission. The dip stick is held in a tube; the end of the tube extends into the transmission. It has measurement markings on it. If you pull it out, you can see whether you have enough transmission fluid, or whether you need more by the level of fluid on the markings. Most manual transmissions do not have dipsticks, instead they use a filler hole which is at the same level as the correct oil level. When the oil is topped up or refilled, the mechanic simply adds oil until the filler hole’s level is reached.

Transmission Gears

Most cars have from three to five forward gears, and one reverse gear. The transmission changes the ratio of the engine speed and the wheels by connecting gears in various combinations. First gear connects the engine power to the drive wheels via a pair of reduction gear sets, which gives increased power and reduced wheelspeed when the car is beginning to move. Gears work exactly like levers. A small gear driving a larger one gives an increase in torque, and a decrease in speed, and vise-versa. Transmission gears are heat-treated, high quality steel. They have smooth, hard teeth, cut on precision machinery while red hot. There are many types of gear teeth, but most transmissions use spur and helical gears. Most of the gears are the helical type, because they last longer and are more quiet than spur gears. There has to be enough room (a few thousandths of an inch) between the gear teeth for lubrication, expansion, and any irregularities in size.

Transmission tunnel

The transmission tunnel is a cone-shaped formation in the front of the floor pan. Its shape duplicates the transmission, but it is a little bit bigger and provides about two inches of clearance around the transmission. The transmission tunnel does not exist in front wheel drive cars, because the transmission is on the side of the engine completely under the hood. Only rear-wheel drive cars have transmission tunnels. A manual transmission tunnel has a hole in it to allow the shift linkage to be worked from inside the car. The shifter linkage goes through the transmission tunnel. A rubber boot on the shifter linkage stops dirt, dust and exhaust fumes from entering the passenger compartment. The rubber boot is mounted onto the transmission tunnel and fastened securely around the gearshift linkage. Vehicles with automatic transmission do not need a transmission tunnel because the shift linkage does not usually go through the transmission tunnel. The shift linkage in automatic transmission usually goes in front of the firewall from the base of the steering column.

Tyres

A tyre is a tubular corded carcass covered with rubber or synthetic rubber, which is mounted on a wheel and inflated to provide traction for moving a vehicle and for assisting the brakes in stopping it.

Universal Joint (U-joint)

The Universal joint (U-joint) connects the drive shaft to the transmission output shaft and the differential pinion gear shaft. This joint must be flexible enough to allow changes in the driving angle (road incline) and the drive shaft. This way, the torque is constantly transmitted when the rear axle is moving up and down. Smaller U-joints are used to route the turning motion of the steering wheel through the steering column to the steering box. There are two types of U-joints, the cross and roller type and the ball and trunnion type. The cross and roller type is used the most; it allows the drive shaft to bend. The ball and trunnion type less frequently used; it allows the drive shaft to bend and also permits backward and forward motion of the drive shaft.

Vacuum Hoses and Motors

Vacuum lines are a series of hoses, or tubing, to the intake manifold. These hoses supply vacuum to various components of the engine, such as the emissions control system. Most air conditioning systems have vacuum motors to open and close the doors on the air conditioning ducts. A vacuum motor is just a small diaphragm with connecting rods to activate the valves of the system. They have the advantages of simplicity and quietness.

Vacuum Pump

Most of the fuel pumps have a vacuum booster section that operates the windshield wipers at an almost constant speed. The fuel section then functions in the same way as ordinary fuel pumps. One difference is that the rotation of the camshaft eccentric in the vacuum pump also operates the vacuum booster section by actuating the pump arm, which pushes a link and the bellows diaphragm assembly upward, expelling air in the upper chamber through its exhaust valve out into the intake manifold. On the return stroke of the pump arm, the diaphragm spring moves the bellows diaphragm down, producing a suction in the vacuum chamber. The suction opens the intake valve of the vacuum section and draws air through the inlet pipe from the windshield wipers. When the wipers are not operating, the intake manifold suction (vacuum) holds the diaphragm up against the diaphragm spring pressure so that the diaphragm does not function with every stroke of the pump arm. When the vacuum is greater than the suction produced by the pump, the airflows from the windshield wiper through the inlet valve and vacuum chamber of the pump and out the exhaust valve outlet to the manifold, leaving the vacuum section inoperative. With high suction in the intake manifold, the operation of the wiper will be the same as if the pump were not installed. When the suction is low, as when the engine is accelerated or operating at high speed, the suction of the pump is greater than that in the manifold and the vacuum section operates the wipers at a constant speed.

Valve Cover

The valve cover covers the valve train. The valve train consists of rocker arms, valve springs, push rods, lifters and cam (in an overhead cam engine). The valve cover can be removed to adjust the valves. Oil is pumped up through the pushrods and dispersed underneath the valve cover, which keeps the rocker arms lubricated. Holes are located in various places in the engine head so that the oil recirculates back down to the oil pan. For this reason, the valve cover must be oil-tight; it is often the source of oil leaks. One way to determine if your valve cover is bent is to remove the gasket and put the valve cover back on to the cylinder head. When the valve cover and cylinder head come into contact, the cover should sit flat. If it rocks, it is bent. A symptom of a bent or leaking valve cover is a pinching of the valve cover gasket. This means that the gasket is sealing one area and not sealing another area. This condition produces a leak; oil could be leaking down the side of the engine. Some valve covers are hard to access, because they are covered with other engine parts. Chronic valve cover leakage can sometimes be fixed by using two gaskets glued together instead of using just one.

Valve Lifter

The valve lifter is the unit that makes contact with the valve stem and the camshaft and rides on the camshaft. It opens the valve when the cam lobes push it upwards. The engine oil comes into the lifter body under pressure. It passes through a little opening at the bottom of an inner piston to a cavity underneath the piston. The oil forces the piston upward until it contacts the push rod. When the cam raises the valve lifter, the pressure is placed on the inner piston, which tries to push the oil back through the little opening. It can’t do this, because a small check valve seals the opening. When the cam goes upward, the lifter solidifies and lifts the valve. Then, when the cam goes down, the lifter is pushed down by the push rod. It adjusts automatically to remove clearances.

Valve Ports

Valve ports are openings in the cylinder head. Intake ports let the fuel mixture into the cylinder head, and exhaust ports let the exhaust out.

Valve Seals

The valve seal is a unit that goes over the end of the valve stem. It keeps excess oil from getting between the valve guide and the valve stem.

Valve Springs

The valve springs keep the valves closed tightly against their seats until the cam opens the valve. After the cam turns (releasing pressure), the valve springs close the valves.

Valves

The valve opens and close the valve ports. If the ports were always open, the fuel exploded in the combustion chamber would leave through the ports. The explosion has to be kept in the combustion chamber to push the piston down. The valves are set up to open and close at exactly the right moment. One lets the fuel mixture in and closes. After the fuel explodes and pushes the piston down, the other valve lets the exhaust out.

Visor

The visor is a flat sunshade and is usually movable. It is attached to the interior of the car at the top of the windshield. Visors protect the eyes of the driver and passengers from the sun’s glare.

Voltage Regulator

The voltage regulator controls voltage and current output of the alternator by automatically cutting resistance in or out of the field circuit to keep it in a safe value. Varying the resistance alters the amount of current passing through the field. When the battery becomes fully charged, the resistance is cut into the field circuit and the charging rate is decreased. In electromagnetic regulators, the voltage regulator unit limits voltage output by controlling the amount of current applied to the rotating field. The field relay on these regulators connects the alternator field windings and voltage regulator windings directly to the battery. The conventional cutout relay unit has been eliminated by the diodes in the alternator. The current regulator has also been eliminated by the current-limiting characteristic of the alternator design. Basically, in a transistorized or an electronic regulator, the transistor is switched on and off to control the alternator field current. The frequency of switching depends on the alternator speed and accessory load, with the possibility that the on-off cycle may be repeated as often as 7000 times per second. The transistorized units have a voltage limiter adjustment. The electronic units are factory calibrated and sealed. They are also nonadjustable

Water (Coolant) Jackets

Water Jackets are used in cars to keep them cool. It is a collection of passages within the block and head, which let the coolant circulate around the “hot spots” (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off. The engine block is actually manufactured in one piece with the water jackets cast into the block and cylinder head. At normal operating temperature, the water pump forces the coolant through the head gasket openings and on into the water jackets in the cylinder head. It flows around in there, cooling everything off by absorbing the heat. After doing its thing, the coolant flows through the upper hose to the radiator where it releases the heat. Then, the water pump sends it back down into the engine’s water jackets to continue the cooling process. On the sides of the engine are “freeze” or “expansion” plugs, which are sheet metal plugs pressed into a series of holes in the block, and are designed to hold the pressure of the cooling system. However, they pop out if the coolant in the block ever freezes.

Wheel (Slave) Cylinder

The wheel cylinder, also called the brake cylinder or slave cylinder, is a cylinder in which movable piston(s) convert hydraulic fluid pressure into mechanical force. The piston(s) within the cylinder move the brake shoes or pads against the braking surface of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. The cylinder is usually made up of a single-bore cylinder casting, an internal compression spring, two pistons, two rubber cups or seals, two rubber boots to prevent entry of dirt and water, and a bleeder screw (valve). In drum type brakes, the wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the toe end of each brake shoe. In disc brakes, the wheel cylinder is part of the caliper. As the brake pedal is depressed, it moves pistons within the master cylinder, forcing hydraulic brake fluid through the brake lines and into cylinders at each wheel. The fluid under pressure causes the wheel cylinders’ pistons to move, which forces the shoes or pads against the brake drums or rotors. Two-way pressure is applied when the wheel cylinder is activated. Brake fluid enters the center of the cylinder, forcing the pistons apart. Pushrods at the piston ends then apply equal pressure to the brake shoes. When pressure is released, a return spring pulls the pistons together.

Wheel Lugs

The large bolts that go through the wheel rim and secure it to the wheel hub are known as the wheel lugs. They are pressed into the hub from the inboard side so they cannot pull out when tightened. The lug nuts thread onto the wheel lugs, clamping the wheel rim between the hub and lug nuts. If the wheel lug nuts are not properly tightened your wheel will come off. Over- tightening, conversely, can prevent you from being able to change a flat tire.

Wheel Well

The wheel well is either plastic or metal. Metal wheel wells are usually part of the body shell. Metal wheel wells strengthen the structure of the car because of their shape, and because they are strongly welded to the body shell. Most rear wheel wells are made of metal. Wheel wells are coated with a rock-proof, rubberized coating underneath to prevent the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they hit. The front wheels are often made of plastic. This is because it is harder to mount the engine with the front wheel wells in place. Plastic wheel wells can be removed, and are easier to mount the engine during the manufacturing of the car.

Wheels

Wheels come in many different designs and usually fall into two categories: stamped sheet metal and machine castings. Some wheels are a combination of the two. Generally cast alloy wheels are higher priced, but have greater strength than stamped sheet metal wheels. The most common are the stamped sheet metal wheels because they are less expensive to produce and are adequate for most uses. Some cars have wire wheels, which consist of three basic components; inner rings, outer rings, and a series of spokes, which connect the two. Cast aluminum wheels are very popular, magnesium wheels are also popular. Both are popular because they are lightweight and strong.

Windshield

Most windshields are stationary. They are fixed in place with a weather-strip made of rubber, which has a groove on the inside and a groove on the outside. The inside groove holds the glass; the outside groove holds the metal rim of the windshield opening in place. The glass “floats” in a plastic sealant that is spread out between the edge of the glass and the frame of the windshield. Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it is struck during a collision. The glass sticks to the plastic to eliminate glass from flying around the interior and injuring someone.

Windshield Washers

All cars use an electric pump-operated windshield washer with a positive displacement washer pump. On some, the motor is placed in the washer reservoir, while on others, it is driven by a wiper motor. When the pump is attached to the wiper motor, the four lobe cam starts a spring-loaded follower, but the pump does not operate all the time that the wiper motor is running. This is because the pumping mechanism is locked out and pumping action occurs.

Windshield Wipers

Most cars have an intermittent wiper system, which permits the driver to select a delayed wipe that operates only every few seconds. A representative wiper/washer unit is the wiper assembly, which incorporates a depressed park system that places the wiper blades below the hood line in the parked position. The relay control uses a relay coil, relay armature, and switch assembly. It controls starting and stopping of the wiper through a latching mechanism. An electric washer pump is mounted on the gear box section of the wiper. The wiper unit gear assembly drives it.

Wires and Cables

Wires and cables conduct electricity. Usually, they are made of annealed copper and are used to carry electricity to the various electrical devices and equipment on passenger cars and trucks. Wire and cable sizes are expressed by a gauge number, which indicates the cross-sectional area of the conductor. The larger the diameter of the wire or cable, the smaller the gauge size number. Cables are made of several strands of wire. The cross-sectional area is equal to the circular mil area of a single strand times the number of strands.

Air Conditioner Maintenance

We all need Air Conditioners in our cars, but there is a negative side to this too. CFC based refrigerant causes terrible damage to the ozone layer. Our mechanics will have to make sure that there are no leaks, and fix them if there are, before they can add any R-12 to our air conditioning systems. Naturally, this cost will be passed along to us. Recovered refrigerant will be recycled. Capturing refrigerants and restoring them for reuse is not only environmentally sound, but mechanically safe. Each molecule of CFC in the atmosphere has a 120 year life that will destroy tens of thousands of ozone molecules. This means that a CFC molecule released in 1991 will still be damaging the ozone layer in 2100.

Air Ducts

The air ducts control the passage of hot or cold air into the interior of the car. They are operated by a control on the dash, either manually or automatically.

Air Pump

The air pump pumps compressed air into the exhaust manifold and in a few cases to the catalytic converter. The oxygen in the pressurized air helps to burn quite a bit of any unburned hydrocarbons (fuel) and thereby converts the poisonous carbon monoxide into good old carbon dioxide. A belt from the engine drives the air pump. It has little vanes (thin, flat, curved fins) that draw the air into the compression chamber. Here, the air is compressed and sent off to the exhaust manifold where it speeds up the emissions burning process. Stainless steel nozzles are used to shoot the air into the exhaust manifold, because they will not burn. Some engines use a pulse air injection system. Pulses of exhaust gases are used by the system to operate an air pump that delivers air into the exhaust system.

Alternator or Generator

The chief source of power of the electrical system is the alternating-current generator, or alternator. Its shaft is driven by the same belt that spins the fan and it keeps the engine running. It converts mechanical energy into alternating-current electricity, which is then channeled through diodes that alter it to direct current for the electrical system and for recharging the battery.

Ammeter

The device is used to determine whether the electrical system is charging, discharging, or staying “level”. The gauge should dip when the engine is started, then go up as the alternator re- charges the battery. After a few minutes, it should go to its middle position.

Automatic Transmissions

Automatic transmission has made driving a lot easier to drive and than manual transmission. The best part is that you don’t have to use a clutch pedal or gearshift lever. An automatic transmission manages all of this on its own. Automatic transmissions automatically change to higher and lower gears with changes in the car’s speed and the load on the engine. These transmissions are also aware of how far down you have pushed the gas pedal, and shift accordingly.

The output shaft turns the governor. The rolling of the governor is directly proportional to the speed of the car. The centrifugal force from the governor sends the oil is sent from the pump to the shift valves. The shift valves then move out sending the transmission fluid to the gear shifting mechanisms in the transmission. When the car slows down, the valves move in and send the transmission fluid in the opposite direction, thus changing the gears. The different gears are selected by routing the pressure to the clutches and brake bands.

Ball Bearings

A ball bearing is an antifriction bearing consisting of a hardened inner and outer race with a series of hardened steel balls separating the two. “Sealed” bearings have plastic dust seals and are greased only at the time of manufacture.

Battery

The battery is the vehicle’s initial source of energy used to start the engine. The battery is then taken over the alternator to supply the car’s electrical needs and to restore energy to the battery. A 12-volt storage battery consists of layers of positively and negatively charged lead plates that, together with their insulated separators, make up each of six two-volt cells. The fluid in the cells are electricity-conducting liquid (electrolyte) that is usually two-thirds distilled water and one-third sulfuric acid. Spaces between the immersed plates provide the most exposure to the electrolyte. The interaction of the plates and the electrolyte produces chemical energy that becomes electricity when a circuit is formed between the negative and positive battery terminals

Battery Charging Methods

As the battery charging methods vary, take into consideration the following, (1) electrical capacity of the battery being serviced; (2) temperature of electrolyte; (3) battery state of charge at start of charging period; and (4) the age and condition of the battery. Follow step by step instructions on the manufacturer’s battery charger guide, or ideally, use an automatic battery charger that senses battery voltage and automatically shuts off – or almost shuts off – when the battery reaches or approaches the fully charged state.

Battery Cables

These are used to connect the battery to the rest of the starting and charging circuits. The battery cables must be of sufficient size to carry such heavy current as a starting motor will draw about 200 amps of current. The cables are prone to corroding as they are close to the battery and therefore it is important that the cables make good electrical contact with the cable clamps. Similarly, clamps must make good electrical contact with the battery posts. Any looseness or corrosion could result in high resistance and consequent voltage drop.

Battery Terminals

The points which connect the wires are called the battery points. The “post” type terminals are being phased out by the “side-mount” type of terminals which use a bolt to screw into the side of the battery and clamp on the battery wire. The vapors from battery acid causes corrosion to form on the lead surfaces, which makes it necessary to clean these periodically. Be sure to wash your hands thoroughly as the corrosion on the terminals is acidic!

Body

The body shell is a fairly complex assortment of large steel sections. These sections have been stamped into specific shapes that make up the body of your car. These parts are designed to do many jobs at once; protect the occupants from the elements and in collisions, provide solid mounts for all other systems, and to slice through the air with minimal resistance. The body also has one other job which is usually important to the owner… it has to look good! Although the zillions of parts that make up a car are all very important, it is also important that the car’s body be able to make riding in a car bearable for you. The body and the suspension system give us a smooth ride, and cushion us from the jarring of the road. Improvements in the body of the car are carried out so that it should go forward with as little up-and-down, and side-to-side movement as possible.

Brake Animation

This animation demonstrates the basics of hydraulic disc and drum brakes in action. As the brake pedal is pressed, the piston in the master cylinder sends pressure (via the brake lines) to the wheel cylinders within the caliper and the drum brake. The pad-to-disc and shoe-to-drum friction stops the vehicle, converting its momentum into heat energy.

Brake Cooling Ducts

Brakes tend to lose their effectiveness if they get hot. Cool air to be directed onto the brakes, increasing braking potential and reducing brake fade. The air dam has a small opening, behind which runs a small tube to the backing plate. This allows cool air to be directed onto the brakes, increasing braking potential and reducing brake fade.

Brake Fluid

Brake fluid is a special liquid used in hydraulic brake systems. It should be impervious to heat, freezing, thickening, and bubbling. There are different types of brake fluids made for different types of systems. These should never mixed. Be sure of what you use in the master cylinder reservouir, because, if the brake fluid gets contaminated, you’d have to change all of the piston seals and hoses. It should be noted that brake fluid is highly corrosive to paint, and care should be used not to get it on your car’s finish.

Brake Pedal

The brake pedal is located on the left side of the accelerator pedal and it slows down or stops the vehicle. The brake shoes and friction pads are forced into contact with the brake drums and rotors to slow the rotation of the wheels. The friction between the tires and the road surface then slows the speed of the vehicle. The pedal is solidly mounted to the firewall, and works as a force-multiplying lever. If the power assist fails, the pedal’s leverage allows you to generate pounds of pressure at each wheel cylinder. A brake pedal should not sink more than an inch or two, no matter how hard it is pressed with the foot. Warning: Any change in this is a cause for serious concern.

Calibrated Friction Brake

A calibrated friction brake is included in the fuel tank unit. This prevents the wave motions of the fuel from fluctuating the pointer on the dash unit, so that the fuel reading will correctly correspond to the amount of fuel available in the tank.

Catalytic Converter

A catalytic converter prevents noxious gases like hydrocarbons, carbon monoxide and nitrogen oxides from polluting the environment by converting them into water vapor and carbon dioxide. The catalytic converter is installed in the exhaust line, between the exhaust manifold and the muffler, and makes use of chemicals that act as a catalyst. The harmful gases enter the catalytic converter, which is a kind of stainless steel container. This is lined with chemicals such as aluminum oxide, platinum and palladium. These chemicals cause the carbon monoxide and hydrocarbons to change into water vapor and carbon dioxide. Some converters have a third lining of chemicals, platinum and rhodium, that reduce nitrogen oxides (three-way, dual bed converter).

Clutch

The clutch allows to connect and disconnect the engine and the transmission while starting up and during shifts. Friction plates route the rotation of the engine crankshaft to the gears, and then to the wheels. It takes the rotation up slowly, so that you aren’t off to a screeching start. In a manual transmission, the clutch is disengaged when you press the pedal down. The pedal works the thrust pad, and it presses levers in the middle of the clutch cover. Doing all this lifts the pressure plate away from the clutch plate. The flywheel (which is turned by the crankshaft from the transmission shaft) gets disconnected. When you lift the clutch pedal, springs force the pressure plate and clutch plate against the flywheel. The clutch plate friction linings allow it to slide before becoming engaged. The sliding causes a smooth start instead of a jolt.

Clutch Pedal, Cables and Levers

One way to activate the throw-out fork of the clutch is by using a system of levers and cables. These levers and cables are connected between the clutch pedal and the throw-out fork. When you press the clutch pedal with your foot, the pressure is transmitted to the fork through the cable and lever arrangement.

Clutch Plate

The clutch plate is a thin, steel, disc whose center is connected to the transmission input shaft by a grooved piece of metal, or hub. The disc is covered with material that is similar to the break linings. This material allows the clutch to slip smoothly and quietly.

Compressor

The job of the compressor is to move liquid refrigerant around in a pipe. The compressor pumps, or forces, the liquid from the evaporator into a condenser and expansion valve, and then back to the evaporator. There are three common types of compressors:

• Two-cylinder reciprocating piston type
• Four cylinder RADIAL type
• Six cylinder AXIAL type

The engine drives the compressor with a belt. In action, the compressor takes the low pressure refrigerant from the evaporator and compresses it according to speed and air temperature. The inlet side is known as the low (pressure) side and the outlet side is known as the high (pressure) side. The compressor compresses the refrigerant, and raises its temperature higher than that of the surrounding air. Then, the compressor forces the refrigerant into the condenser.

Compressor Relay

A capillary tube from a cycling switch lets the switch know what the temperature is in the evaporator. This switch turns the compressor on and off to keep the evaporator temperature at about 32 to 45 degrees F. The relay switch keeps moisture from freezing on the evaporator core.

Condenser

The condenser is a long tube that goes back and forth through a multitude of cooling fins. It is mounted in front of the radiator to take advantage of the forced air provided by the fan and the motion of the car. As the highly pressurized refrigerant (vapor) flows into the condenser, it gives off heat and warms the condenser. This causes the condenser to be hotter than the forced air coming through the condenser. The condenser hands its heat off to the forced air and turns the refrigerant back into cool liquid in the expansion valve, where it heads back to the evaporator

Coolant (Antifreeze)

Coolant (antifreeze) is a complex chemical liquid helps prevent freezing in cold climates, so that cars can operate in sub zero temperatures, and boils at a higher temperature than water. Besides this, it also lubricates the water pump as it flows through. Some antifreeze compounds are specially formulated for aluminum radiators. Keep the coolant somewhere between 20 and 60 percent of the mixture in your car, depending on the car and climactic conditions. Do not use a strong antifreeze mixture as it can cause leaks in your car’s cooling system. Coolant is extremely poisonous and should be handled with care. If it spills on the ground it can kill stray animals that drink it.

Crankshaft

The crankshaft converts the up and down motion of the pistons into a rotary motion. It provides the turning motion for the wheels. It works much like the pedals of a bicycle, converting up-down motion into rotational motion. The crankshaft is usually either alloy steel or cast iron. The crankshaft is connected to the pistons by the connecting-rods. Some parts of the shaft do not move up and down; they rotate in the stationary main bearings. These parts are known as journals. There are usually three journals in a four cylinder engine.

Dash Controls

The dash board, behind the steering wheel displays the control panel of the car. Duplicate fragments of the control panel are found in the interior of your vehicle, such as automatic door locks, extra light switches, etc. Many functions of the car are carried out through the dash board, like turning on the headlights, windshield wipers, horn, turn signals, air conditioning, cassette player, etc. It also contains all of your gauges; gas, temperature, tachometer, etc., which enables the monitoring of the operating conditions of your engine and charging system, fuel level, oil pressure and coolant temperature. It ensures that all the controls are within the drivers reach.

Diesel Fuel Injector

The diesel fuel injector is a pressure valve, but it has specific components that allow it to disperse the diesel fuel in set patterns, depending on the design of the valve. Diesel fuel injectors receive the pressurized impulse from the diesel fuel pump, and allow the fuel to enter the combustion chamber when it is needed. If the diesel fuel injectors get clogged, engine performance suffers.

Diesel Fuel Pump

Diesel fuel pumps inject a specific amount of fuel during a specific time, and control the injectors by the pressure waves of the fuel that they pump. The diesel fuel pump has mechanisms in it, which allows more or less fuel to be pumped. If less fuel is pumped into the cylinders, this slows the engine, and vice versa. It thus also regulates the speed. A series of gears link them to the crankshaft or the camshaft, allowing the fuel pump to be driven directly by the crankshaft of the engine. Some may be belt or chain driven.

Differential

The differential is the thing that works both drive axles at the same time, but lets them rotate at different speeds so that the car can make turns. When a car makes a turn, the outer wheel has to turn faster than the inner wheel, due to the difference in the length of the paths they take. The differential is located between the two wheels, and is attached to each wheel by a half-shaft rotated through a bevel gear. Four-wheel drive cars have a separate differential for each pair of wheels. A grooved, or splined, axle side gear is positioned on the splined end of each axle. The side gears are driven by “spider” gears, which are little gears mounted on a shaft attached to the differential case. As it is supported by the differential case, the side gear can turn inside the case. The differential case can be turned, revolving around the axle gears. The differential pinion (a pinion is a small gear that either drives a larger gear or is driven by one) shaft turns the ring gear, which is fastened to the differential case. The propeller shaft (drive shaft) connects the transmission output shaft to the differential pinion shaft. The turning differential case is mounted on two large bearing holders. These bearings are called carrier bearings. The propeller shaft rotates the ring gear pinion, and the pinion turns the ring gear. The ring gear then turns the differential case and pinion shaft, but the axle side gears will not turn. By passing the differential pinion shaft through two differential pinion gears that mesh with the side gears, the case will turn and the axle side gears will turn with it. During turns, the side gears turn at rates dictated by the radius of the turns, and the spider gears then turn to allow the outer wheel to turn faster than the inner one.

Drive Shaft

The drive shaft, or propeller shaft, connects the transmission output shaft to the differential pinion shaft. Since all roads are not perfectly smooth, and the transmission is fixed, the drive shaft has to be flexible to absorb the shock of bumps in the road. Universal, or “U-joints” allow the drive shaft to flex (and stop it from breaking) when the drive angle changes. There are two types of drive shafts, the Hotchkiss drive and the Torque Tube Drive.

Drive Wheel/Axle

The drive wheel is the end of the axle shaft; it has lugs protruding from it. The lugs are separate pieces that are mounted in the drive wheel. The drive wheel bolts onto the brake drum and the wheel rim of the car itself. It is usually a disc about six or seven inches in diameter. Occasionally the drive wheel and the axle shaft are all one piece.

Dynamic Wheel Balance

“Dynamic” balance is the equal distribution of weight on each side of the vertical centerline of the wheel and tire assembly. Unbalance on either or both sides of a plane of rotation, called dynamic unbalance, causes the wheels to bounce, resulting in flat spots on the tire tread and worn ball joints, tie rod ends, steering gears, and shock absorbers. Dynamic unbalance in the front wheels will cause them to wobble.

EGR Valve

The Exhaust Gas Recirculation (EGR) valve sends some of the exhaust gas back into the cylinders to reduce combustion temperature. This is required because nitrous oxides (nasty pollutants) form when the combustion temperature gets above 2,500 degrees F. This is as a result of the formation of nitrous oxides when the nitrogen in the air mixes with the oxygen. When it’s sunny, the nitrous oxides from the exhaust get together with the hydrocarbons in the air to form smog. This is when the EGR valve comes in handy. By recirculating some of the exhaust gas back through the intake manifold to the cylinders, we can lower the combustion temperature. Lowering the combustion temperature lowers the amount of nitrous oxide produced. Consequently, less of it comes out the tail pipe. There are two types of EGR valves. One operates through the use of a vacuum, and the other operated through the use of pressure. Both types allow the exhaust gas in to lower the combustion temperature when it gets too high.

Electric Fuel Pump

Used previously for heavier vehicles, they have only recently become operational in cars. The replacement types usually use a diaphragm arrangement like the mechanical pumps, except that it is actuated by an electrical solenoid. It uses a small turbine wheel driven by a constant speed electric motor. The entire unit is located in the fuel tank and submerged in the fuel itself. When the engine is running the pump pump operates continuously, thus exerting a constant pressure which supplies the maximum fuel demands of the engine. When less fuel is required, the pump does not deliver at full potential, because the turbine is not a positive displacement type like the mechanical pump. Consequently, the turbine will run without pumping fuel and so, needs no means of varying fuel delivery rate like its mechanical counterpart. Since the fuel can flow past the spinning turbine blades, there is no need for pump inlet and outlet valves nor is there any need to vary its speed. A relay for the electric fuel pump is used to complete the circuit to the fuel pump. This cuts off current to the fuel pump in the event of an accident.

Electronic Fuel Injection

Injectors are opened by solenoids operated by an electronic control unit, as opposed to mechanical injection systms. Since the fuel has no resistance to overcome, other than insignificant friction losses, the pump pressure can be set at very low values, consistent with the limits of obtaining full atomization with the type of injectors used. The control unit, depending on the operating conditions of the engine, determines the amount of fuel to be injected. The conditions depend on manifold pressure, accelerator enrichment, cold-start requirements, idling conditions, outside temperature and barometric pressure. The systems work with constant pressure and with ‘variable timed’ or ‘continuous flow’ injection. The advantages. To begin with, it has fewer moving parts, no need for ultra-precise machining standards and quieter operation. Also, there is less power loss, a low electrical requirement, no need for special pump drives, no critical fuel filtration requirements, no surges or pulsations in the fuel line. More than anything else, it costs lesser than its mechanical counterpart.

Evaporator

The evaporator is a long tube, or coil, that goes back and forth through a multitude of cooling fins. The refrigerant is a liquid when it enters the evaporator. A fan blows warm air over the evaporator and causes the liquid refrigerant to boil. After it has absorbed the heat from the warm air, the warm air isn’t warm anymore. The same blower that blows the warm air (that is now “cool” air) over the evaporator, keeps on blowing it into the interior of your car, and you have — air conditioning! The evaporator also removes the moisture from the air coming through its fins and turns it into water. The water just drains off. The temperature of the evaporator coil can go from 33 degrees F to 0 degrees F. If it goes below 32 degrees F, the moisture that’s supposed to drain off the coils will freeze. This makes for a very (surprise!) inefficient system, so a thermostatic switch is used to connect and disconnect it to the compressor as necessary.

Exhaust Manifold and Header

Usually constructed of cast iron, the exhaust manifold is a pipe that conducts the exhaust gases from the combustion chambers to the exhaust pipe. It has smooth curves in it for improving the flow of exhaust. The exhaust manifold is bolted to the cylinder head, and has entrances for the air that is injected into it. It is usually located under the intake manifold. A header is a different type of manifold; it is made of separate equal-length tubes.

Fan Clutch

The fan clutch is a small fluid coupling with a thermostatic device and controls a variable-speed fan. It ensures that the fan will rotate at just the right speed to keep the engine from overheating, and reduces drive to the fan when it is no longer needed. The fan clutch has a fluid coupling partly filled with silicone oil designed for just that purpose. When the temperature of the air passing through the radiator rises, the heat alerts a bimetal coil spring to “uncoil” or expand. When it expands, it allows just a little more oil to enter the fluid coupling, so the fluid coupling starts to rotate the fan. If the air coming through the radiator is cool, the opposite happens; the coil spring contracts, the oil leaves the fluid coupling and the fan slows. Slowing the fan when it is not needed reduces fuel consumption, makes less noise and saves engine power. Sometimes a flat bimetal strip spring is used instead of a coil spring; it bows out and in when the temperature rises and drops, letting oil in and out of the fluid coupling.

Filler Cap (Brake Fluid Reservoir Cover)

The cap on the brake fluid reservoir has a hole for air, or is vented, to allow the fluid to expand and contract without creating a vacuum or causing pressure. A rubber diaphragm goes up and down with the fluid level’s pressure, and keeps out any dust or moisture.

Flywheel

The large wheel connected to the crankshaft provides the momentum to keep the crankshaft turning without the application of power, through the energy generated during the power stroke. This energy is also used to drive the crankshaft, connecting rods and pistons during the three idle strokes of the 4-stroke cycle. This makes for a smooth engine speed. The flywheel forms one surface of the clutch and is the base for the ring gear.

Frame (Chassis)

The basic structure of the vehicle is the frame and it provides a good anchor point for the suspension system. There are two types of frames; integral frames, or ‘unibody’, and conventional frames. A conventional frame is basically a ‘one-piece’ frame; or two ‘one-piece’ frames fastened together. These frames are extremely rigid to keep all the parts of the car in perfect alignment, which are attached to it. It is constructed of heavy steel and welded or cold riveted together. Cold riveting keeps the rivets from shrinking after they cool off. The integral, or unibody, frame is just the opposite. With this type of frame, the body parts are used to structurally strengthen the entire car, and all of the sections are welded into one piece. Sometimes the parts of the body and the suspension system are attached and reinforced. Also, some unibody frames have partial front and rear frames for attaching the engine and suspension members.

Fuel Pump

The fuel pump has three functions: to deliver enough fuel to supply the requirements of an engine under all operating conditions, to maintain enough pressure in the line between the carburetor and the pump to keep the fuel from boiling, and to prevent vapor lock. Excessive pressure causes the carburetor float needle off its seat its seat resulting in high fuel level in the float chamber, leading to high fuel consumption. Highest pressure occurs at idling speed and the lowest at top speed.

Fuel Tank

The fuel tank stores the excess fuel until it is needed for operation of the vehicle. The fuel tank has an inlet pipe and an outlet pipe. The outlet pipe has a fitting for fuel line connection and may be located in the top or in the side of the tank. The lower end is about one-half inch above the bottom of the tank so that collected sediment will not be flushed out into the carburetor. The bottom of the tank contains a drain plug so that tank may be drained and cleaned

Gaskets

Gaskets and seals the secure machined joints, and prevent fluids and gasses (oil, gasoline, coolant, fuel vapor, exhaust, etc.) from leaking. The cylinder head has to keep the water in the cooling system at the same time as it contains the combustion pressure. Gaskets made of steel, copper and asbestos are used between the cylinder head and engine block. Because the engine expands and contracts with heating and cooling, it is easy for joints to leak, so the gaskets have to be soft and “springy” enough to adapt to expansion and contraction. They also have to make up for any irregularities in the connecting parts

Headlights

Headlights are mounted on the front of the car to light the road ahead during night or foggy days. They have reflectors and special lenses and are usually the sealed beam construction type, with the filament, reflector and lens fused together into an airtight unit. The most popular type of headlight is the halogen type, because it provides bright illumination. The halogen bulb is filled with pressurized gas (halogen) and can produce flying fragments if shattered. Wear protective glasses for changing a halogen lamp and always throw out the old one in the protective carton that comes with the new one.

Heat Exchanger

The “heat exchanger” is a device that uses exhaust heat to aid in fuel evaporation. It usually is built into the intake manifold as an area where the hot exhaust gasses and fuel-air mixture come close to each other.

Heater Core

The heater core is a smaller version of the radiator that is used to keep your toes warm when it’s cold outside. It is mounted under the dashboard. Some of the hot coolant is routed through this little radiator, by more hoses. A small electric fan is also mounted there especially for the purpose of directing the heat inside the car. The principle is exactly the same as the one used in the radiator for your engine, except that the heat is released inside the car instead of outside.

Hood

The car’s hood consists of an inner and an outer panel. The inner panel provides strength, while the outer panel is just a metal cover. The underside of the hood is often covered with a sound-absorbing material. Some high performance cars have ‘hood scoops’ which channel outside air directly to the air filter, which gives improved performance and efficiency. The hood release is a small lever, which is usually mounted under the dash. It is connected to the hood latch by a cable. The hood latch has a safety feature, which requires a second latch to be released before the hood will open. This is to prevent accidental opening while driving.

Ignition Circuit

An ignition circuit is made up of two sub-circuits: the primary, which carries low voltage; and the secondary, which carries high voltage. The primary circuit is controlled by the ignition key. It releases 12 volts of electricity from the battery or alternator through the coil to a set of breaker points in the lower part of the distributor, or to the relay in electronic ignition applications. When the points or relay are closed, current flows through the chassis back to the battery, completing the circuit. When the points or relay are open, the flow stops, causing a high-voltage surge to pass from the coil through a rotor in the top of the distributor to the spark plugs. Once the car has started, the voltage regulator protects the battery from being overcharged by the alternator. part of the low -voltage current is absorbed by the condenser when the points are open.

Idler Gears

These are small gears which are not directly linked to anything. Idle gears are used to reduce or increase rotation speeds, and reverse directions of rotation. The center gear would be considered an idle gear, if three gears are connected in a string.

Indicator Needle

This is the pointer on your gauge that shows you the gauge’s current reading. Its examples are those found in your speedometer, temperature gauge, tachometer and oil pressure gauge.

Intake Stroke

The first stroke is called the intake stroke. The piston moves down the cylinder, creating a partial vacuum in the cylinder. A mixture of air and fuel is then forced through the inlet valve into the cylinder by atmospheric pressure, now greater than the pressure in the cylinder. The exhaust valve stays closed during the stroke.

Knock Sensor

The knock sensor senses when fuel is burning unevenly and causing “knocking” or irregular vibrations in the engine. It consists of an electric coil that is wound around two ceramic rods with a magnet in the center. The vibration of the engine causes the rods to vibrate. This disturbs the coil’s magnetic field and alters the current passing through the coil. This disturbance returns to the computer as a signal pattern that the computer analyzes. The computer then determines whether the vibrations are characteristic of engine knocking.

Lever Return Spring

A return spring, or restoring spring, is a coil spring that moves something, such as a valve or diaphragm back to its normal position and holds it there.

Lighting Circuit

The automobile lighting circuit includes the wiring harness, all the lights, and the various switches that control their use. The complete circuit of the modern passenger car can be broken down into individual circuits, each having one or more lights and switches. In each separate circuit, the lights are connected in parallel, and the controlling switch is in series between the group of lights and the fuse box. The parking lights, are connected in parallel and controlled by a single switch. In some installations, one switch controls the connection to the fuse box, while a selector switch determines which of two circuits is energized. The headlights, with their upper and lower beams, are an example of this type of switch. Again, in some cases, such as the courtesy lights, several switches may be connected in parallel so that any switch may be used to turn on the lights.

Lifter Body

The valve lifter body houses the valve lifter mechanism. The valve lifter is the unit that makes contact with the valve stem and the camshaft. It rides on the camshaft. When the cam lobes push it upwards, it opens the valve.

Limiting Coil and Operating Coil

The limiting coil passes the current from the battery to the common connection of two coils at the lower terminal on the dash unit. This current may pass from either the operating coil of the dash unit and the other over to the tank sending unit. When the fuel tank is low or empty, the sliding brush cuts out all resistance in the tank unit. Then the current will passes through the tank unit circuit because of the low resistance, and only a small portion will pass through the operating coil to the dash unit. This coil is not magnetized enough to move the dash unit pointer, which is then held at the “Empty” position by the limiting coil.

When the tank is full or partly full, the float of the tank unit will rise to the surface of the fuel and move the sliding brush over the rheostat, putting resistance in the tank unit circuit. This results in more current will then passing through the operating coil to give a magnetic pull on the pointer, which overcomes some of the pull of the limiting coil. When the tank is full, the tank unit circuit contains the maximum resistance to the flow of the current. The operating coil will then receive its maximum current and exert pull of the pointer to give a “Full” reading. As the tank empties, the operating coil loses some of its magnetic pull and the limiting coil will still have about the same pull so that the pointer is pulled toward the lower reading.

Main Bearings

The main bearing secure the crankshaft in its place. The largest number of main bearings a crankshaft can have is one more than the number of cylinders, but it can have one less bearing than the number of cylinders. Not only do the bearings support the crankshaft, but one bearing must control the forward-backward movement of the crankshaft. This bearing rubs against a ground surface of the main journal, and is called the “thrust bearing.”

Manifold to Exhaust Pipe Gaskets

There are several types of gaskets that connect the exhaust pipe to the manifold. One is a flat surface gasket. Another type uses a ball and socket with springs to maintain pressure. This type allows some flexibility without breakage of the seal or the manifold. A third type is the full ball connector type, which also allows a little flexibility.

Muffler

The muffler serves to muffle the noise coming out of the engine. Exhaust gases leave the engine under extremely high pressure. If these gases escaped directly from the engine the noise would be tremendous. Therefore, the exhaust manifold sends the gases to a muffler where they go through metal plates, or tubes, with a series of holes. The pressure of the gases is reduced when they pass through the muffler, so they go out of the tail pipe quietly. Made of metal, the muffler is located underneath the body of the car. It is connected between the tail pipe and the catalytic converter. There are two types of muffler designs. While one type uses several baffled chambers to reduce noise, the other sends the gases straight through perforated pipe wrapped in metal or fiberglass. This type of muffler is designed for the purpose of reducing backpressure and, consequently, makes slightly more noise.

Nuts and Bolts

Nuts are hexagon shaped metal objects with a threaded hole through them so that they can be attached to bolts. Bolts are cylindrical objects with groves on the outside, which enable them to be screwed into nuts. A bolt without an end is classified as a ‘lug’ or ‘stud’. There are many grades of nuts and bolts. Grades depend on the quality of the materials and the tolerances observed during the manufacture of the nuts and bolts. Nuts and bolts are often separated by washers. Washers have many shapes and sizes. They give the nut and the bolt a firm hardened surface for bedding against. The parts that you put together with nuts and bolts are usually not as strong as the nuts and bolts themselves. The washers allow the nuts and bolts to be fully tightened down, providing a wider area to spread out the force of the tightening and they keep the nuts and bolts from digging into the material when they are tightened.

Oil Filler Cap

The oil filler cap is a plastic or metal cap that covers an opening into the valve cover. It allows you to add oil when the dipstick indicates that you need it. Some cars have the crankcase vented through the filler cap. Oil which is added through the filler passes down through openings in the head into the oil sump at the bottom of the engine.

Oil Gauge

The Oil Gauge lets you know the pressure in the oil pump; and is a direct indicator of the condition of your engine. If the oil gauge gives very low readings, it means that your oil pressure has dropped. The engine would soon grind to a halt if the oil is not forced into the nooks and crannies that need to be oiled.

Overhead Valve (OHV)

In an overhead valve (OHV) engine, the valves are mounted in the cylinder head, above the combustion chamber. Usually this type of engine has the camshaft mounted in the cylinder block, and the valves are opened and closed by push rods.

Parking Brake

The parking brake holds one or more brakes continuously in the applied position. The parking brake employs the regular drum brakes on the rear wheel. Instead of hydraulic pressure, however, a simple mechanical linkage is used to engage the brake shoes. When the parking-brake pedal is depressed (or, in some cars, a hand lever is raised), a steel cable pulls taut a tension lever; other cables draw the brake shoes firmly against the drums. The release knob slackens the cables and disengages the brake shoes. The parking brake is self adjusting. An automatic adjuster in the piston moves on the thrust screw to compensate for lining wear.

Piston, Rings, and Wrist Pin

The piston converts the potential energy of the fuel into the kinetic energy that turns the crankshaft. The piston is a cylindrical shaped hollow part that moves up and down inside the engine’s cylinder. It has grooves around its perimeter near the top where rings are placed. The piston fits snugly in the cylinder. The piston rings are used to ensure a snug “air tight” fit. The wrist pin connects the piston to the connecting rod. Pistons are made of aluminum, because it is light and a good heat conductor. The piston head or “crown” is the top surface against which the explosive force is exerted. It may be flat, concave, convex or any one of a great variety of shapes to promote turbulence or help control combustion. In some, a narrow groove is cut into the piston above the top ring to serve as a “heat dam” to reduce the amount of heat reaching the top ring.

Power Brakes

Power brake are of four general types: vacuum suspended; air suspended; hydraulic booster, and electro-hydraulic booster. Most power brakes use vacuum suspended units, which contain a large vacuum-powered booster device to provide the added thrust to the typical power-brake. Pressure on the brake pedal pushes forward a rod connected to the pistons of the two master cylinders. The pistons begin forcing fluid into the front and rear brake lines. At the same time, the brake-pedal pushrod positions the vacuum-control valve so that it closes the vacuum port and seals off the forward half of the booster unit. The engine vacuum line then draws off the air, creating a low-pressure vacuum chamber. Atmospheric pressure in the control chamber then pushes against the diaphragm, dividing the two chambers. The pressure on the diaphragm, which is locked to the pushrod, forces it forward, supplying even more pressure on the pistons. The safe driver is always ready to apply the total force needed to stop their vehicle, even if the engine quits (removing the power assist).

Push Rod

A push rod is a connecting link in an operating mechanism. Two examples are the rod between the valve lifter and rocker arm on an overhead valve engine, and push rods at the piston ends which apply pressure to the brake shoes.

Rear View Mirror

The rear view mirror is a wide rectangular mirror that you (the driver) use to view anything behind the car. You don’t have to take your eyes off the road to turn your head around. On most cars, the rear view mirror has a “day/night” selection switch that tilts the mirror inside its glass housing without tilting the exterior glass housing itself. The switch tilts the mirror upward, about five degrees, to divert the majority of the light striking the mirror up on to the headliner of the car. The light that you see when the mirror is on the “night” setting is actually bouncing off the glass housing (a good reason to keep it clean). The percentage of light reflected into your eyes in the night position, is very small compared to the amount that would normally be reflected into your eyes in its normal position.

Radial Tyres

In radials tyres the ply or ply cords are alligned at 90 degrees to the circumference. While radials improve performance the fact is that they are not very good for bad roads and overloading. The suspension of a vehicle has, also, to be modified to accept radials. Radials offer much better grip of the road especially on surfaces which offer poor wheel traction like wet of slippery roads.

Radiator

The radiator is used to dissipate the heat that the coolant has absorbed from the engine. It is constructed to hold a large amount of water in tubes or passages which provide a large area in contact with the atmosphere. It generally consists of a radiator core, with its water-carrying tubes and large cooling area, which are connected to a receiving tank (end cap) at the top and to a dispensing tank at the bottom. Side flow radiators have their “end caps” on the sides, which allows a lower hood line. While in operation, water is pumped from the engine to the top (receiving) tank, where it spreads over the tops of the tubes. As the water passes down through the tubes, it loses its heat to the airstream, which passes around the outside of the tubes. To help spread the heated water over the top of all the tubes, a baffle plate is often placed in the upper tank, directly under the inlet hose from the engine. Sooner or later, almost everyone has to deal with an overheating car. Since water is readily available, it is not beyond the ability of most people to add some to their radiator if it’s low.

Radiator Cap (Pressure Cap)

The radiator cap is more than a cap for your radiator; it keeps your engine cool by sealing and pressurizing the coolant inside it. It is designed to hold the coolant in the radiator under a predetermined amount of pressure. If it was not kept under pressure, it would begin to boil, and soon all the coolant would have boiled away. However, the radiator (or pressure) cap prevents this from happening by exerting enough pressure to keep the coolant from boiling. If your cooling system is under too much pressure, it can “blow its top”! To prevent this, the radiator cap has a pressure relief valve. The valve has a preset rating that allows it to take just up to a certain amount of pressure. When you turn the cap on the filler neck of the radiator, you seal the upper and lower sealing surfaces of the filler neck. The pressure relief valve spring is compressed against the lower seal when you lock the cap. The radiator filler neck has an overflow tube right between the two sealing surfaces. If the pressure in the cooling system exceeds the preset rating of your cap, its pressure relief valve allows the lower seal to be lifted from its seat. Then the excess pressure (coolant, air) can squish through the overflow tube to the ground or the coolant reservoir. Once enough pressure has been released (the caps preset rating), the pressure relief valve is again closed by the spring. The pressure cap can be tested with a cooling system pressure tester, using an adapter, to make certain that it is living up to its pressure rating. It should be replaced if it fails the test. It should be noted that most radiator pressure caps are not meant to be removed, and that the coolant should always be added through the expansion (overflow) tank. If you happen to remove the radiator cap from a hot engine, the pressure can cause steam to shoot out and seriously burn you.

Radiator Grille

The radiator grille is the part of the body shell on the front of your car that covers the area where the air enters. The radiator grille can also be part of the bumper on some cars. The radiator is connected to the shroud for the radiator, which directs the air that comes in through the radiator grille to the radiator only. This prevents the air from escaping around the radiator and failing to cool the engine. On newer cars, the radiator grille has been lowered to take advantage of lower hood lines, brought about by an effort to increase fuel efficiency. Older cars had massive grilles, whereas the cars now produced have smaller more aerodynamic grilles.

Radiator Shroud

The radiator shroud prevents the recirculation of air around the fan. It is usually a plastic hood that encloses the fan to guide the air through the core, and stop it from coming back around and through the fan again. It also protects you from the fan blades!

Rear End Tunnel

The rear end tunnel provides clearance for the drive shaft and the housing of the differential. It allows the rear end to travel up and down with suspension motion; it clears the differential housing by a maximum of three or four inches when the suspension is fully compressed. Often forming the front of the trunk floor, it is attached to the wheel wells on each side as well as the floor pan and the trunk floor.

Reverse-flow Muffler

The reverse-flow has multiple pipes, and is used to lessen the noise made from an automobile. Four chambers and a double jacket are used to accomplish muffling of the exhaust noise. Exhaust gases are directed to the third chamber, forced forward to the first chamber, from where they travel the length of the muffler and are exhausted into the tail pipe.

Ring Gear

The ring gear is connected to the differential case. A ring gear attached to a pinion gear and shaft turns the differential case. The propeller shaft connects the transmission output shaft to the differential pinion shaft. It is connected to the ring gear pinion shaft.

Roller Bearings

They are used in wheel bearing applications. They consist of

1. An inner “race” which is a hardened ring that is slightly tapered on the outside and
2. An outer race, a hardened ring that is slightly tapered on the inside and
3. A set of rollers contained in a cage. These bearings must not be crushed together, (the angle of assembly drives them together) creating friction if they are tightened too far. Roller bearings need to be repacked periodically with fresh grease to insure a long life.

Rotary Engine

The rotary engine applies power directly to the transmission. Its construction allows it to provide the power of a conventional engine that is twice its size and weight and that has twice as many parts. A large combustion chamber in the form of a pinched oval, called an epitrochoid is the basic unit of the rotary engine. Within this chamber all four functions of a piston take place simultaneously in the three pockets that are formed between the rotor and the chamber wall. Just as the addition of cylinders increases the horsepower of a piston-powered engine, so the addition of combustion chambers increases the power of a rotary engine. Larger cars may eventually use rotaries with three or four rotors.

Rotary Valve

The “rotary valve” is the key to the operation of power steering. It directs the power steering fluid under pressure to either side of the rack piston, which converts hydraulic power to mechanical force. Friction from the wheel causes a torsion bar in the rotary valve to deflect. This changes the position of the valve spool and sleeve, directing fluid under pressure to the proper end of the power cylinder. The difference in pressure on either side of the piston (which is attached to the rack) helps move the rack to reduce turning effort

Seat Belts and Air Bags

Air bags protected occupants in ways that seat belts alone cannot. The air bag spreads out the violent impact of a crash and kept occupants from smashing against the steering wheel, dashboard or windshield. Having an air bag and wearing an effective seat belt is the best protection. By this, you are protected from frontal crashes by the air bag — you are also protected by the seat belt in all other types of crashes. With an “effective” safety belt, your body will stop, in a crash, before you hit or go through the windshield and parts of your car. Seat belts are especially important in small cars, because your chances of being killed or badly hurt in a collision with a big car is eight times greater. Wearing your belt will greatly improve your chances of survival. Air bags can reduce the risk of death in a head-on collision by 26%% and in all serious accidents by 13%.

WITHOUT A BELT, AIR BAGS ARE OF SLIGHT BENEFIT

Air bags are only useful in frontal crashes, so it is not a good idea to skip your seat belt because you have an air bag. Air bags provide very effective protection in frontal crashes, inflating instantly to protect the driver or passenger that has an air bag. They spread the impact of the crash over the individual’s head and chest and protect fragile body parts from the car’s hard surfaces. Many basic improvements have been introduced into cars in recent years. These include anti-burst door latches, safety glass, energy-absorbing steering wheels and columns, head restraints and various seat belt systems. The benefits of the three-point seat belts have been firmly established: over 50%% of fatal and serious injuries to car occupants would be avoided if all occupants wore their seat belts.

Seats

There are basically two types of seats; bench seats or bucket seats. A bucket seat is a low, separate seat for one person. Although we think of them as relatively new, it is interesting to note that in 1905 Henry Ford’s first model had bucket seats. Bench seats are a continuous cushion and backrest across the width of the car (although some vans might have them running along the length of the van). Bucket seats are single units with a separation between the left and right seats. Usually vinyl leather and fabric are used for upholstery.

“Flatsprings” are used for comfort, which are pieces of wire bent into a zigzag pattern. Both ends of the wire are attached to the seat frame, with additional lengths added every six inches. Foam padding is used to cover the flatsprings. The front seats ride on rails that are bolted to the floor. This arrangement allows the seats to move backwards and forwards to suit the driver or passenger. The seat adjustment lever is attached to a latch that fits into teeth along the rail. Moving the lever releases the seat, and allows the seat to move. At any point of the seat’s movement, releasing the lever engages the latch with one of the teeth. Usually there is also a pull-spring; this draws the seat forward when the latch is released. The rear seat usually doesn’t move, because it is secured to the floor of the car. It’s backrest is attached to the partition between the passenger compartment and trunk.

Secondary Brake Shoe

The Secondary brake shoe is the shoe in a set that is energized by the primary shoe. A brake shoe is a carrier to which the brake lining is attached, used to force the lining in contact with the brake drum or rotor. When brakes are applied, the brake shoes or friction pads are forced into contact with the brake drums or rotors to slow the rotation of the wheels. The vehicle slows down as a result of the friction between the tires and the road surface.

Shock Absorber Struts

A strut is a structural piece designed to resist pressure in the direction of its length. On typical “McPherson Strut” use, the shock absorber is built into the strut. Most shock absorber struts are hydraulic units. Like the hydraulic shock struts, faulty units must be replaced as an assembly. Another similar front suspension system is called the “hydraulic shock strut.” This strut serves as a shock absorber and replaces the upper control arm. The coil spring, however, is located between the lower control arm and the body structure instead of being mounted directly on the strut.

Shock Absorbers

The operating principle of direct-acting hydraulic shock absorbers is in forcing fluid through restricting openings in the valves. This restricted flow serves to slow down and control rapid movement in the car springs as they react to road irregularities. Usually, fluid flow through the pistons is controlled by spring-loaded valves and the hydraulic shock absorber automatically adapts to the severity of the shock. If the axle moves slowly, resistance to the flow of fluid will be light. If it is rapid or violent, the resistance is stronger, since more time is required to force fluid through the openings. By these actions and reactions, the shock absorbers permit a soft ride over small bumps and provide firm control over spring action for cushioning large bumps. The double-acting units must be effective in both directions because spring rebound can be almost as violent as the original action that compressed the shock absorber.

Side Beam

The operating principle of direct-acting hydraulic shock absorbers is in forcing fluid through restricting openings in the valves. This restricted flow serves to slow down and control rapid movement in the car springs as they react to road irregularities. Usually, fluid flow through the pistons is controlled by spring-loaded valves and the hydraulic shock absorber automatically adapts to the severity of the shock. If the axle moves slowly, resistance to the flow of fluid will be light. If it is rapid or violent, the resistance is stronger, since more time is required to force fluid through the openings. By these actions and reactions, the shock absorbers permit a soft ride over small bumps and provide firm control over spring action for cushioning large bumps. The double-acting units must be effective in both directions because spring rebound can be almost as violent as the original action that compressed the shock absorber.

Solar Cells

Some electric cars are equipped with solar cells located on the roof of the car, similar to a sunroof. These collect sunlight and convert it into energy. The solar cell is used to augment the existing recharging system.

Spark Plug

A spark plug is a device that is inserted into the combustion chamber of an engine, which contains a side electrode and insulated center electrode. These are spaced to provide a gap for firing an electrical spark to ignite air-fuel mixtures. The high-voltage burst from the coil via the distributor is received at the spark plug’s terminal and conducted down a center electrode protected by a porcelain insulator. At the bottom of the plug, which projects into the cylinder, the voltage must be powerful enough to jump a gap between the center and side electrodes through a thick atmosphere of fuel mixture. Fuel is ignited in the cylinder when the spark bridges the gap.

Spark Plug Wires

The spark plug wire carries 20,000 or more volts from the distributor cap to the spark plug. Spark plug wires are made of various layers of materials. The fiber core, inside the spark plug wire carries the high voltage. Some spark plug wires have a locking connection at the distributor cap. The distributor cap must first be removed and the terminals squeezed together, and then the spark plug wire can be removed from the distributor cap. To work effectively in modern ignition systems, it is important that the resistor ignition cable is capable of producing a specifically designed resistance.

Speedometer Cable

The speedometer cable is connected either to the gearbox output shaft, transmission shaft, or differential. Speed and record mileage is measured by the rotation of these shafts. This information is sent back through the cable where it is recorded on the speedometer. The speedometer and odometer are driven by a cable housed in a flexible casing, which is connected to a gear in the transmission. Speedometer cables break as the result of age, lack of lubrication, or because the cable casing has sharp bends. It may also break from too much friction in the speedometer head.

Speedometer and Odometer

The analog speedometer that is used on cars indicates its speed and records the distance the car has traveled. A speedometer is driven by a flexible cable connected to the speedometer pinion in the transmission. Speedometers are calibrated in miles per hour and/or in kilometers. The instrument records the distance traveled in miles or kilometers. That portion of the instrument is known as the odometer. Most odometers record the total distance traveled. Some also record the distance of individual trips.

Spoiler

A spoiler is a kind of wing that is mounted on the rear of the car in a horizontal position. Its function is to provide high-speed stability. In most cars, the spoiler is purely cosmetic, as a car has to be going over 100 mph to take advantage of the aerodynamics of the spoiler. Some mini-vans also make use of a spoiler, but it’s upside down, and angled. This type of a rear spoiler only keeps the rain off the rear window.

Springs

There are two kinds of springs, leaf springs and coil springs. Springs have life spans that are determined by the number of cycles they can withstand over a certain period of time. If a spring breaks while a car is being driven, the car will suddenly lurch downward. The bottom of the car might be damaged, or you might lose your muffler! Leaf springs are made of individual springs, or plates. If you break one plate of your leaf spring, it won’t be noticeable, but your car might begin to lean to one side or the other. Coil springs, if they break, will suddenly drop the front or rear end of your car and impair driving under the normal conditions of full suspension travel.

Starter

The starter converts electricity to mechanical energy in two stages. Turning on the ignition switch releases a small amount of power from the battery to the solenoid above the starter. This creates a magnetic field that pulls the solenoid plunger forward, forcing the attached shift yoke to move the starter drive so that its pinion gear meshes with the engine’s crankshaft flywheel. When the plunger completes its travels, it strikes a contact that permits a greater amount of current to flow from the battery to the starter motor. The motor then spins the drive and turns the meshed gears to provide power to the crankshaft, which prepares each cylinder for ignition. After the engine starts, the ignition key is released to break the starting circuit. The solenoid’s magnetic field collapses and the return spring pulls the plunger back, automatically shutting off the starter motor and disengaging the starter drive. When the starter is not in use, the drive unit is retracted so that its pinion is disengaged from the flywheel. As soon as the starter is activated, the forward movement of the solenoid plunger causes the shift yoke to move the drive in the opposite direction and engage the pinion and flywheel. The pinion is locked to its shaft by a clutch that unlocks if the engine starts up and the flywheel begins turning the pinion faster than its normal speed. By allowing the pinion to spin freely for a moment, the clutch protects the motor from damage until the drive is retracted.

Starter Circuit

The starter circuit is activated when the ignition switch is turned on, thereby opening a second switch in the solenoid, permitting a second flow of electricity from the battery to the starter motor. The engine cranking circuit is made up of a battery, starting motor, ignition switch, and electrical wiring. On placing the ignition switch in the “start” position, the solenoid windings are energized and the resulting shift lever movement causes the drive pinion gear to engage the flywheel ring gear, and cranking takes place. When the engine starts, an overrunning clutch (part of the drive assembly) protects the armature from too much speed until the switch is opened. At this time, a return spring causes the pinion gear to disengage from the flywheel.

Steering Arms

The steering arms pick up motion from the relay rods and the tie rods, causing the steering knuckles to turn the wheels. They are not used in rack-and-pinion setups.

Steering Systems

The manual steering system incorporates:
1. steering wheel and column,
2. a manual gearbox and pitman arm or a rack and pinion assembly,
3. linkages; steering knuckles and ball joints; and
the wheel spindle assemblies. Power steering systems add a hydraulic pump; fluid reservoir; hoses; lines; and either a power assist unit mounted on, or integral with, a power steering gear assembly. There are several different manual steering gears in current use. The “rack and pinion” type is the choice of most manufacturers.

Stoplight Switch

To signal a stop, a brake pedal operated “stoplight switch” is provided that operates the vehicle’s stop lamps. In addition to lighting the conventional rear lights, the switch also operates the center high-mounted stop lamp, which became mandatory on later models. Cruise control equipped vehicles may also utilize a vacuum release valve. In this case, movement of the brake pedal actuates both the vacuum release valve and the stoplight switch.

Sway Bar

Some cars require stabilizers to steady the chassis against front-end roll and sway on turns. Stabilizers control this centrifugal tendency that forces a rising action on the side toward the inside of the turn. When the car turns and begins to lean over, the sway bar uses the upward force on the outer wheel to lift on the inner wheel, thus keeping the car more level.

Thrust Bearings

Thrust bearings are similar to ball bearings except that the plates that the balls ride between are designed as flat washers. The balls riding between these washers reduce side-to-side load. These are used inside of the transmission, rear end and many other areas of the car.

Tie Rod Ends

Tie rod ends are utilized in the steering linkage, steering knuckle pivot supports, and various other hinge mechanisms. Ball joints that join the key parts of the steering linkage pass on the steering wheel’s motion no matter what the angle of the linkage or the vibration from the road.

Timing Chain/ Belt

The automobile engine uses a metal timing chain, or a flexible toothed timing belt to rotate the camshaft. The timing chain/belt is driven by the crankshaft. The timing chain, or timing belt is used to “time” the opening and closing of the valves. The camshaft rotates once for every two rotations of the crankshaft.

Torsion Bars

Torsion bar suspension uses the flexibility of a steel bar or tube, twisting lengthwise to provide spring action. Two rods of spring steel are used in this type of suspension. One end of the bar is fixed solidly to a part of the frame behind the wheel; the other is attached to the lower control arm. As the arm rises and falls with wheel movement, the bar twists and absorbs more of the road shocks before they can reach the body of the car. Just like a spring that rebounds after it has been compressed, the bar untwists when the pressure is released. Adjusting the torsion bars controls the height of the front end of the vehicle. The adjusting bolts are located at the torsion bar anchors in the front crossmember. The inner ends of the lower control arms are bolted to the crossmember and pivot through a bushing.

Transmission Fluid Dip Stick

The transmission fluid dip stick is a long metal rod that goes into the transmission. It serves check how much transmission fluid is in the transmission. The dip stick is held in a tube; the end of the tube extends into the transmission. It has measurement markings on it. If you pull it out, you can see whether you have enough transmission fluid, or whether you need more by the level of fluid on the markings. Most manual transmissions do not have dipsticks, instead they use a filler hole which is at the same level as the correct oil level. When the oil is topped up or refilled, the mechanic simply adds oil until the filler hole’s level is reached.

Transmission Gears

Most cars have from three to five forward gears, and one reverse gear. The transmission changes the ratio of the engine speed and the wheels by connecting gears in various combinations. First gear connects the engine power to the drive wheels via a pair of reduction gear sets, which gives increased power and reduced wheelspeed when the car is beginning to move. Gears work exactly like levers. A small gear driving a larger one gives an increase in torque, and a decrease in speed, and vise-versa. Transmission gears are heat-treated, high quality steel. They have smooth, hard teeth, cut on precision machinery while red hot. There are many types of gear teeth, but most transmissions use spur and helical gears. Most of the gears are the helical type, because they last longer and are more quiet than spur gears. There has to be enough room (a few thousandths of an inch) between the gear teeth for lubrication, expansion, and any irregularities in size.

Transmission tunnel

The transmission tunnel is a cone-shaped formation in the front of the floor pan. Its shape duplicates the transmission, but it is a little bit bigger and provides about two inches of clearance around the transmission. The transmission tunnel does not exist in front wheel drive cars, because the transmission is on the side of the engine completely under the hood. Only rear-wheel drive cars have transmission tunnels. A manual transmission tunnel has a hole in it to allow the shift linkage to be worked from inside the car. The shifter linkage goes through the transmission tunnel. A rubber boot on the shifter linkage stops dirt, dust and exhaust fumes from entering the passenger compartment. The rubber boot is mounted onto the transmission tunnel and fastened securely around the gearshift linkage. Vehicles with automatic transmission do not need a transmission tunnel because the shift linkage does not usually go through the transmission tunnel. The shift linkage in automatic transmission usually goes in front of the firewall from the base of the steering column.

Tyres

A tyre is a tubular corded carcass covered with rubber or synthetic rubber, which is mounted on a wheel and inflated to provide traction for moving a vehicle and for assisting the brakes in stopping it.

Universal Joint (U-joint)

The Universal joint (U-joint) connects the drive shaft to the transmission output shaft and the differential pinion gear shaft. This joint must be flexible enough to allow changes in the driving angle (road incline) and the drive shaft. This way, the torque is constantly transmitted when the rear axle is moving up and down. Smaller U-joints are used to route the turning motion of the steering wheel through the steering column to the steering box. There are two types of U-joints, the cross and roller type and the ball and trunnion type. The cross and roller type is used the most; it allows the drive shaft to bend. The ball and trunnion type less frequently used; it allows the drive shaft to bend and also permits backward and forward motion of the drive shaft.

Vacuum Hoses and Motors

Vacuum lines are a series of hoses, or tubing, to the intake manifold. These hoses supply vacuum to various components of the engine, such as the emissions control system. Most air conditioning systems have vacuum motors to open and close the doors on the air conditioning ducts. A vacuum motor is just a small diaphragm with connecting rods to activate the valves of the system. They have the advantages of simplicity and quietness.

Vacuum Pump

Most of the fuel pumps have a vacuum booster section that operates the windshield wipers at an almost constant speed. The fuel section then functions in the same way as ordinary fuel pumps. One difference is that the rotation of the camshaft eccentric in the vacuum pump also operates the vacuum booster section by actuating the pump arm, which pushes a link and the bellows diaphragm assembly upward, expelling air in the upper chamber through its exhaust valve out into the intake manifold. On the return stroke of the pump arm, the diaphragm spring moves the bellows diaphragm down, producing a suction in the vacuum chamber. The suction opens the intake valve of the vacuum section and draws air through the inlet pipe from the windshield wipers. When the wipers are not operating, the intake manifold suction (vacuum) holds the diaphragm up against the diaphragm spring pressure so that the diaphragm does not function with every stroke of the pump arm. When the vacuum is greater than the suction produced by the pump, the airflows from the windshield wiper through the inlet valve and vacuum chamber of the pump and out the exhaust valve outlet to the manifold, leaving the vacuum section inoperative. With high suction in the intake manifold, the operation of the wiper will be the same as if the pump were not installed. When the suction is low, as when the engine is accelerated or operating at high speed, the suction of the pump is greater than that in the manifold and the vacuum section operates the wipers at a constant speed.

Valve Cover

The valve cover covers the valve train. The valve train consists of rocker arms, valve springs, push rods, lifters and cam (in an overhead cam engine). The valve cover can be removed to adjust the valves. Oil is pumped up through the pushrods and dispersed underneath the valve cover, which keeps the rocker arms lubricated. Holes are located in various places in the engine head so that the oil recirculates back down to the oil pan. For this reason, the valve cover must be oil-tight; it is often the source of oil leaks. One way to determine if your valve cover is bent is to remove the gasket and put the valve cover back on to the cylinder head. When the valve cover and cylinder head come into contact, the cover should sit flat. If it rocks, it is bent. A symptom of a bent or leaking valve cover is a pinching of the valve cover gasket. This means that the gasket is sealing one area and not sealing another area. This condition produces a leak; oil could be leaking down the side of the engine. Some valve covers are hard to access, because they are covered with other engine parts. Chronic valve cover leakage can sometimes be fixed by using two gaskets glued together instead of using just one.

Valve Lifter

The valve lifter is the unit that makes contact with the valve stem and the camshaft and rides on the camshaft. It opens the valve when the cam lobes push it upwards. The engine oil comes into the lifter body under pressure. It passes through a little opening at the bottom of an inner piston to a cavity underneath the piston. The oil forces the piston upward until it contacts the push rod. When the cam raises the valve lifter, the pressure is placed on the inner piston, which tries to push the oil back through the little opening. It can’t do this, because a small check valve seals the opening. When the cam goes upward, the lifter solidifies and lifts the valve. Then, when the cam goes down, the lifter is pushed down by the push rod. It adjusts automatically to remove clearances.

Valve Ports

Valve ports are openings in the cylinder head. Intake ports let the fuel mixture into the cylinder head, and exhaust ports let the exhaust out.

Valve Seals

The valve seal is a unit that goes over the end of the valve stem. It keeps excess oil from getting between the valve guide and the valve stem.

Valve Springs

The valve springs keep the valves closed tightly against their seats until the cam opens the valve. After the cam turns (releasing pressure), the valve springs close the valves.

Valves

The valve opens and close the valve ports. If the ports were always open, the fuel exploded in the combustion chamber would leave through the ports. The explosion has to be kept in the combustion chamber to push the piston down. The valves are set up to open and close at exactly the right moment. One lets the fuel mixture in and closes. After the fuel explodes and pushes the piston down, the other valve lets the exhaust out.

Visor

The visor is a flat sunshade and is usually movable. It is attached to the interior of the car at the top of the windshield. Visors protect the eyes of the driver and passengers from the sun’s glare.

Voltage Regulator

The voltage regulator controls voltage and current output of the alternator by automatically cutting resistance in or out of the field circuit to keep it in a safe value. Varying the resistance alters the amount of current passing through the field. When the battery becomes fully charged, the resistance is cut into the field circuit and the charging rate is decreased. In electromagnetic regulators, the voltage regulator unit limits voltage output by controlling the amount of current applied to the rotating field. The field relay on these regulators connects the alternator field windings and voltage regulator windings directly to the battery. The conventional cutout relay unit has been eliminated by the diodes in the alternator. The current regulator has also been eliminated by the current-limiting characteristic of the alternator design. Basically, in a transistorized or an electronic regulator, the transistor is switched on and off to control the alternator field current. The frequency of switching depends on the alternator speed and accessory load, with the possibility that the on-off cycle may be repeated as often as 7000 times per second. The transistorized units have a voltage limiter adjustment. The electronic units are factory calibrated and sealed. They are also nonadjustable

Water (Coolant) Jackets

Water Jackets are used in cars to keep them cool. It is a collection of passages within the block and head, which let the coolant circulate around the “hot spots” (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off. The engine block is actually manufactured in one piece with the water jackets cast into the block and cylinder head. At normal operating temperature, the water pump forces the coolant through the head gasket openings and on into the water jackets in the cylinder head. It flows around in there, cooling everything off by absorbing the heat. After doing its thing, the coolant flows through the upper hose to the radiator where it releases the heat. Then, the water pump sends it back down into the engine’s water jackets to continue the cooling process. On the sides of the engine are “freeze” or “expansion” plugs, which are sheet metal plugs pressed into a series of holes in the block, and are designed to hold the pressure of the cooling system. However, they pop out if the coolant in the block ever freezes.

Wheel (Slave) Cylinder

The wheel cylinder, also called the brake cylinder or slave cylinder, is a cylinder in which movable piston(s) convert hydraulic fluid pressure into mechanical force. The piston(s) within the cylinder move the brake shoes or pads against the braking surface of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. The cylinder is usually made up of a single-bore cylinder casting, an internal compression spring, two pistons, two rubber cups or seals, two rubber boots to prevent entry of dirt and water, and a bleeder screw (valve). In drum type brakes, the wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the toe end of each brake shoe. In disc brakes, the wheel cylinder is part of the caliper. As the brake pedal is depressed, it moves pistons within the master cylinder, forcing hydraulic brake fluid through the brake lines and into cylinders at each wheel. The fluid under pressure causes the wheel cylinders’ pistons to move, which forces the shoes or pads against the brake drums or rotors. Two-way pressure is applied when the wheel cylinder is activated. Brake fluid enters the center of the cylinder, forcing the pistons apart. Pushrods at the piston ends then apply equal pressure to the brake shoes. When pressure is released, a return spring pulls the pistons together.

Wheel Lugs

The large bolts that go through the wheel rim and secure it to the wheel hub are known as the wheel lugs. They are pressed into the hub from the inboard side so they cannot pull out when tightened. The lug nuts thread onto the wheel lugs, clamping the wheel rim between the hub and lug nuts. If the wheel lug nuts are not properly tightened your wheel will come off. Over- tightening, conversely, can prevent you from being able to change a flat tire.

Wheel Well

The wheel well is either plastic or metal. Metal wheel wells are usually part of the body shell. Metal wheel wells strengthen the structure of the car because of their shape, and because they are strongly welded to the body shell. Most rear wheel wells are made of metal. Wheel wells are coated with a rock-proof, rubberized coating underneath to prevent the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they hit. The front wheels are often made of plastic. This is because it is harder to mount the engine with the front wheel wells in place. Plastic wheel wells can be removed, and are easier to mount the engine during the manufacturing of the car.

Wheels

Wheels come in many different designs and usually fall into two categories: stamped sheet metal and machine castings. Some wheels are a combination of the two. Generally cast alloy wheels are higher priced, but have greater strength than stamped sheet metal wheels. The most common are the stamped sheet metal wheels because they are less expensive to produce and are adequate for most uses. Some cars have wire wheels, which consist of three basic components; inner rings, outer rings, and a series of spokes, which connect the two. Cast aluminum wheels are very popular, magnesium wheels are also popular. Both are popular because they are lightweight and strong.

Windshield

Most windshields are stationary. They are fixed in place with a weather-strip made of rubber, which has a groove on the inside and a groove on the outside. The inside groove holds the glass; the outside groove holds the metal rim of the windshield opening in place. The glass “floats” in a plastic sealant that is spread out between the edge of the glass and the frame of the windshield. Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it is struck during a collision. The glass sticks to the plastic to eliminate glass from flying around the interior and injuring someone.

Windshield Washers

All cars use an electric pump-operated windshield washer with a positive displacement washer pump. On some, the motor is placed in the washer reservoir, while on others, it is driven by a wiper motor. When the pump is attached to the wiper motor, the four lobe cam starts a spring-loaded follower, but the pump does not operate all the time that the wiper motor is running. This is because the pumping mechanism is locked out and pumping action occurs.

Windshield Wipers

Most cars have an intermittent wiper system, which permits the driver to select a delayed wipe that operates only every few seconds. A representative wiper/washer unit is the wiper assembly, which incorporates a depressed park system that places the wiper blades below the hood line in the parked position. The relay control uses a relay coil, relay armature, and switch assembly. It controls starting and stopping of the wiper through a latching mechanism. An electric washer pump is mounted on the gear box section of the wiper. The wiper unit gear assembly drives it.

Wires and Cables

Wires and cables conduct electricity. Usually, they are made of annealed copper and are used to carry electricity to the various electrical devices and equipment on passenger cars and trucks. Wire and cable sizes are expressed by a gauge number, which indicates the cross-sectional area of the conductor. The larger the diameter of the wire or cable, the smaller the gauge size number. Cables are made of several strands of wire. The cross-sectional area is equal to the circular mil area of a single strand times the number of strands.

Thrust Bearings

Thrust bearings are similar to ball bearings except that the plates that the balls ride between are designed as flat washers. The balls riding between these washers reduce side-to-side load. These are used inside of the transmission, rear end and many other areas of the car.

Tie Rod Ends

Tie rod ends are utilized in the steering linkage, steering knuckle pivot supports, and various other hinge mechanisms. Ball joints that join the key parts of the steering linkage pass on the steering wheel’s motion no matter what the angle of the linkage or the vibration from the road.

Timing Chain/ Belt

The automobile engine uses a metal timing chain, or a flexible toothed timing belt to rotate the camshaft. The timing chain/belt is driven by the crankshaft. The timing chain, or timing belt is used to “time” the opening and closing of the valves. The camshaft rotates once for every two rotations of the crankshaft.

Torsion Bars

Torsion bar suspension uses the flexibility of a steel bar or tube, twisting lengthwise to provide spring action. Two rods of spring steel are used in this type of suspension. One end of the bar is fixed solidly to a part of the frame behind the wheel; the other is attached to the lower control arm. As the arm rises and falls with wheel movement, the bar twists and absorbs more of the road shocks before they can reach the body of the car. Just like a spring that rebounds after it has been compressed, the bar untwists when the pressure is released. Adjusting the torsion bars controls the height of the front end of the vehicle. The adjusting bolts are located at the torsion bar anchors in the front crossmember. The inner ends of the lower control arms are bolted to the crossmember and pivot through a bushing.

Transmission Fluid Dip Stick

The transmission fluid dip stick is a long metal rod that goes into the transmission. It serves check how much transmission fluid is in the transmission. The dip stick is held in a tube; the end of the tube extends into the transmission. It has measurement markings on it. If you pull it out, you can see whether you have enough transmission fluid, or whether you need more by the level of fluid on the markings. Most manual transmissions do not have dipsticks, instead they use a filler hole which is at the same level as the correct oil level. When the oil is topped up or refilled, the mechanic simply adds oil until the filler hole’s level is reached.

Transmission Gears

Most cars have from three to five forward gears, and one reverse gear. The transmission changes the ratio of the engine speed and the wheels by connecting gears in various combinations. First gear connects the engine power to the drive wheels via a pair of reduction gear sets, which gives increased power and reduced wheelspeed when the car is beginning to move. Gears work exactly like levers. A small gear driving a larger one gives an increase in torque, and a decrease in speed, and vise-versa. Transmission gears are heat-treated, high quality steel. They have smooth, hard teeth, cut on precision machinery while red hot. There are many types of gear teeth, but most transmissions use spur and helical gears. Most of the gears are the helical type, because they last longer and are more quiet than spur gears. There has to be enough room (a few thousandths of an inch) between the gear teeth for lubrication, expansion, and any irregularities in size.

Transmission tunnel

The transmission tunnel is a cone-shaped formation in the front of the floor pan. Its shape duplicates the transmission, but it is a little bit bigger and provides about two inches of clearance around the transmission. The transmission tunnel does not exist in front wheel drive cars, because the transmission is on the side of the engine completely under the hood. Only rear-wheel drive cars have transmission tunnels. A manual transmission tunnel has a hole in it to allow the shift linkage to be worked from inside the car. The shifter linkage goes through the transmission tunnel. A rubber boot on the shifter linkage stops dirt, dust and exhaust fumes from entering the passenger compartment. The rubber boot is mounted onto the transmission tunnel and fastened securely around the gearshift linkage. Vehicles with automatic transmission do not need a transmission tunnel because the shift linkage does not usually go through the transmission tunnel. The shift linkage in automatic transmission usually goes in front of the firewall from the base of the steering column.

Tyres

A tyre is a tubular corded carcass covered with rubber or synthetic rubber, which is mounted on a wheel and inflated to provide traction for moving a vehicle and for assisting the brakes in stopping it.

Universal Joint (U-joint)

The Universal joint (U-joint) connects the drive shaft to the transmission output shaft and the differential pinion gear shaft. This joint must be flexible enough to allow changes in the driving angle (road incline) and the drive shaft. This way, the torque is constantly transmitted when the rear axle is moving up and down. Smaller U-joints are used to route the turning motion of the steering wheel through the steering column to the steering box. There are two types of U-joints, the cross and roller type and the ball and trunnion type. The cross and roller type is used the most; it allows the drive shaft to bend. The ball and trunnion type less frequently used; it allows the drive shaft to bend and also permits backward and forward motion of the drive shaft.

Vacuum Hoses and Motors

Vacuum lines are a series of hoses, or tubing, to the intake manifold. These hoses supply vacuum to various components of the engine, such as the emissions control system. Most air conditioning systems have vacuum motors to open and close the doors on the air conditioning ducts. A vacuum motor is just a small diaphragm with connecting rods to activate the valves of the system. They have the advantages of simplicity and quietness.

Vacuum Pump

Most of the fuel pumps have a vacuum booster section that operates the windshield wipers at an almost constant speed. The fuel section then functions in the same way as ordinary fuel pumps. One difference is that the rotation of the camshaft eccentric in the vacuum pump also operates the vacuum booster section by actuating the pump arm, which pushes a link and the bellows diaphragm assembly upward, expelling air in the upper chamber through its exhaust valve out into the intake manifold. On the return stroke of the pump arm, the diaphragm spring moves the bellows diaphragm down, producing a suction in the vacuum chamber. The suction opens the intake valve of the vacuum section and draws air through the inlet pipe from the windshield wipers. When the wipers are not operating, the intake manifold suction (vacuum) holds the diaphragm up against the diaphragm spring pressure so that the diaphragm does not function with every stroke of the pump arm. When the vacuum is greater than the suction produced by the pump, the airflows from the windshield wiper through the inlet valve and vacuum chamber of the pump and out the exhaust valve outlet to the manifold, leaving the vacuum section inoperative. With high suction in the intake manifold, the operation of the wiper will be the same as if the pump were not installed. When the suction is low, as when the engine is accelerated or operating at high speed, the suction of the pump is greater than that in the manifold and the vacuum section operates the wipers at a constant speed.

Valve Cover

The valve cover covers the valve train. The valve train consists of rocker arms, valve springs, push rods, lifters and cam (in an overhead cam engine). The valve cover can be removed to adjust the valves. Oil is pumped up through the pushrods and dispersed underneath the valve cover, which keeps the rocker arms lubricated. Holes are located in various places in the engine head so that the oil recirculates back down to the oil pan. For this reason, the valve cover must be oil-tight; it is often the source of oil leaks. One way to determine if your valve cover is bent is to remove the gasket and put the valve cover back on to the cylinder head. When the valve cover and cylinder head come into contact, the cover should sit flat. If it rocks, it is bent. A symptom of a bent or leaking valve cover is a pinching of the valve cover gasket. This means that the gasket is sealing one area and not sealing another area. This condition produces a leak; oil could be leaking down the side of the engine. Some valve covers are hard to access, because they are covered with other engine parts. Chronic valve cover leakage can sometimes be fixed by using two gaskets glued together instead of using just one.

Valve Lifter

The valve lifter is the unit that makes contact with the valve stem and the camshaft and rides on the camshaft. It opens the valve when the cam lobes push it upwards. The engine oil comes into the lifter body under pressure. It passes through a little opening at the bottom of an inner piston to a cavity underneath the piston. The oil forces the piston upward until it contacts the push rod. When the cam raises the valve lifter, the pressure is placed on the inner piston, which tries to push the oil back through the little opening. It can’t do this, because a small check valve seals the opening. When the cam goes upward, the lifter solidifies and lifts the valve. Then, when the cam goes down, the lifter is pushed down by the push rod. It adjusts automatically to remove clearances.

Valve Ports

Valve ports are openings in the cylinder head. Intake ports let the fuel mixture into the cylinder head, and exhaust ports let the exhaust out.

Valve Seals

The valve seal is a unit that goes over the end of the valve stem. It keeps excess oil from getting between the valve guide and the valve stem.

Valve Springs

The valve springs keep the valves closed tightly against their seats until the cam opens the valve. After the cam turns (releasing pressure), the valve springs close the valves.

Valves

The valve opens and close the valve ports. If the ports were always open, the fuel exploded in the combustion chamber would leave through the ports. The explosion has to be kept in the combustion chamber to push the piston down. The valves are set up to open and close at exactly the right moment. One lets the fuel mixture in and closes. After the fuel explodes and pushes the piston down, the other valve lets the exhaust out.

Visor

The visor is a flat sunshade and is usually movable. It is attached to the interior of the car at the top of the windshield. Visors protect the eyes of the driver and passengers from the sun’s glare.

Voltage Regulator

The voltage regulator controls voltage and current output of the alternator by automatically cutting resistance in or out of the field circuit to keep it in a safe value. Varying the resistance alters the amount of current passing through the field. When the battery becomes fully charged, the resistance is cut into the field circuit and the charging rate is decreased. In electromagnetic regulators, the voltage regulator unit limits voltage output by controlling the amount of current applied to the rotating field. The field relay on these regulators connects the alternator field windings and voltage regulator windings directly to the battery. The conventional cutout relay unit has been eliminated by the diodes in the alternator. The current regulator has also been eliminated by the current-limiting characteristic of the alternator design. Basically, in a transistorized or an electronic regulator, the transistor is switched on and off to control the alternator field current. The frequency of switching depends on the alternator speed and accessory load, with the possibility that the on-off cycle may be repeated as often as 7000 times per second. The transistorized units have a voltage limiter adjustment. The electronic units are factory calibrated and sealed. They are also nonadjustable

Water (Coolant) Jackets

Water Jackets are used in cars to keep them cool. It is a collection of passages within the block and head, which let the coolant circulate around the “hot spots” (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off. The engine block is actually manufactured in one piece with the water jackets cast into the block and cylinder head. At normal operating temperature, the water pump forces the coolant through the head gasket openings and on into the water jackets in the cylinder head. It flows around in there, cooling everything off by absorbing the heat. After doing its thing, the coolant flows through the upper hose to the radiator where it releases the heat. Then, the water pump sends it back down into the engine’s water jackets to continue the cooling process. On the sides of the engine are “freeze” or “expansion” plugs, which are sheet metal plugs pressed into a series of holes in the block, and are designed to hold the pressure of the cooling system. However, they pop out if the coolant in the block ever freezes.

Wheel (Slave) Cylinder

The wheel cylinder, also called the brake cylinder or slave cylinder, is a cylinder in which movable piston(s) convert hydraulic fluid pressure into mechanical force. The piston(s) within the cylinder move the brake shoes or pads against the braking surface of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. The cylinder is usually made up of a single-bore cylinder casting, an internal compression spring, two pistons, two rubber cups or seals, two rubber boots to prevent entry of dirt and water, and a bleeder screw (valve). In drum type brakes, the wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the toe end of each brake shoe. In disc brakes, the wheel cylinder is part of the caliper. As the brake pedal is depressed, it moves pistons within the master cylinder, forcing hydraulic brake fluid through the brake lines and into cylinders at each wheel. The fluid under pressure causes the wheel cylinders’ pistons to move, which forces the shoes or pads against the brake drums or rotors. Two-way pressure is applied when the wheel cylinder is activated. Brake fluid enters the center of the cylinder, forcing the pistons apart. Pushrods at the piston ends then apply equal pressure to the brake shoes. When pressure is released, a return spring pulls the pistons together.

Wheel Lugs

The large bolts that go through the wheel rim and secure it to the wheel hub are known as the wheel lugs. They are pressed into the hub from the inboard side so they cannot pull out when tightened. The lug nuts thread onto the wheel lugs, clamping the wheel rim between the hub and lug nuts. If the wheel lug nuts are not properly tightened your wheel will come off. Over- tightening, conversely, can prevent you from being able to change a flat tire.

Wheel Well

The wheel well is either plastic or metal. Metal wheel wells are usually part of the body shell. Metal wheel wells strengthen the structure of the car because of their shape, and because they are strongly welded to the body shell. Most rear wheel wells are made of metal. Wheel wells are coated with a rock-proof, rubberized coating underneath to prevent the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they hit. The front wheels are often made of plastic. This is because it is harder to mount the engine with the front wheel wells in place. Plastic wheel wells can be removed, and are easier to mount the engine during the manufacturing of the car.

Wheels

Wheels come in many different designs and usually fall into two categories: stamped sheet metal and machine castings. Some wheels are a combination of the two. Generally cast alloy wheels are higher priced, but have greater strength than stamped sheet metal wheels. The most common are the stamped sheet metal wheels because they are less expensive to produce and are adequate for most uses. Some cars have wire wheels, which consist of three basic components; inner rings, outer rings, and a series of spokes, which connect the two. Cast aluminum wheels are very popular, magnesium wheels are also popular. Both are popular because they are lightweight and strong.

Windshield

Most windshields are stationary. They are fixed in place with a weather-strip made of rubber, which has a groove on the inside and a groove on the outside. The inside groove holds the glass; the outside groove holds the metal rim of the windshield opening in place. The glass “floats” in a plastic sealant that is spread out between the edge of the glass and the frame of the windshield. Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it is struck during a collision. The glass sticks to the plastic to eliminate glass from flying around the interior and injuring someone.

Windshield Washers

All cars use an electric pump-operated windshield washer with a positive displacement washer pump. On some, the motor is placed in the washer reservoir, while on others, it is driven by a wiper motor. When the pump is attached to the wiper motor, the four lobe cam starts a spring-loaded follower, but the pump does not operate all the time that the wiper motor is running. This is because the pumping mechanism is locked out and pumping action occurs.

Windshield Wipers

Most cars have an intermittent wiper system, which permits the driver to select a delayed wipe that operates only every few seconds. A representative wiper/washer unit is the wiper assembly, which incorporates a depressed park system that places the wiper blades below the hood line in the parked position. The relay control uses a relay coil, relay armature, and switch assembly. It controls starting and stopping of the wiper through a latching mechanism. An electric washer pump is mounted on the gear box section of the wiper. The wiper unit gear assembly drives it.

Wires and Cables

Wires and cables conduct electricity. Usually, they are made of annealed copper and are used to carry electricity to the various electrical devices and equipment on passenger cars and trucks. Wire and cable sizes are expressed by a gauge number, which indicates the cross-sectional area of the conductor. The larger the diameter of the wire or cable, the smaller the gauge size number. Cables are made of several strands of wire. The cross-sectional area is equal to the circular mil area of a single strand times the number of strands.

Thrust Bearings

Thrust bearings are similar to ball bearings except that the plates that the balls ride between are designed as flat washers. The balls riding between these washers reduce side-to-side load. These are used inside of the transmission, rear end and many other areas of the car.

Tie Rod Ends

Tie rod ends are utilized in the steering linkage, steering knuckle pivot supports, and various other hinge mechanisms. Ball joints that join the key parts of the steering linkage pass on the steering wheel’s motion no matter what the angle of the linkage or the vibration from the road.

Timing Chain/ Belt

The automobile engine uses a metal timing chain, or a flexible toothed timing belt to rotate the camshaft. The timing chain/belt is driven by the crankshaft. The timing chain, or timing belt is used to “time” the opening and closing of the valves. The camshaft rotates once for every two rotations of the crankshaft.

Torsion Bars

Torsion bar suspension uses the flexibility of a steel bar or tube, twisting lengthwise to provide spring action. Two rods of spring steel are used in this type of suspension. One end of the bar is fixed solidly to a part of the frame behind the wheel; the other is attached to the lower control arm. As the arm rises and falls with wheel movement, the bar twists and absorbs more of the road shocks before they can reach the body of the car. Just like a spring that rebounds after it has been compressed, the bar untwists when the pressure is released. Adjusting the torsion bars controls the height of the front end of the vehicle. The adjusting bolts are located at the torsion bar anchors in the front crossmember. The inner ends of the lower control arms are bolted to the crossmember and pivot through a bushing.

Transmission Fluid Dip Stick

The transmission fluid dip stick is a long metal rod that goes into the transmission. It serves check how much transmission fluid is in the transmission. The dip stick is held in a tube; the end of the tube extends into the transmission. It has measurement markings on it. If you pull it out, you can see whether you have enough transmission fluid, or whether you need more by the level of fluid on the markings. Most manual transmissions do not have dipsticks, instead they use a filler hole which is at the same level as the correct oil level. When the oil is topped up or refilled, the mechanic simply adds oil until the filler hole’s level is reached.

Transmission Gears

Most cars have from three to five forward gears, and one reverse gear. The transmission changes the ratio of the engine speed and the wheels by connecting gears in various combinations. First gear connects the engine power to the drive wheels via a pair of reduction gear sets, which gives increased power and reduced wheelspeed when the car is beginning to move. Gears work exactly like levers. A small gear driving a larger one gives an increase in torque, and a decrease in speed, and vise-versa. Transmission gears are heat-treated, high quality steel. They have smooth, hard teeth, cut on precision machinery while red hot. There are many types of gear teeth, but most transmissions use spur and helical gears. Most of the gears are the helical type, because they last longer and are more quiet than spur gears. There has to be enough room (a few thousandths of an inch) between the gear teeth for lubrication, expansion, and any irregularities in size.

Transmission tunnel

The transmission tunnel is a cone-shaped formation in the front of the floor pan. Its shape duplicates the transmission, but it is a little bit bigger and provides about two inches of clearance around the transmission. The transmission tunnel does not exist in front wheel drive cars, because the transmission is on the side of the engine completely under the hood. Only rear-wheel drive cars have transmission tunnels. A manual transmission tunnel has a hole in it to allow the shift linkage to be worked from inside the car. The shifter linkage goes through the transmission tunnel. A rubber boot on the shifter linkage stops dirt, dust and exhaust fumes from entering the passenger compartment. The rubber boot is mounted onto the transmission tunnel and fastened securely around the gearshift linkage. Vehicles with automatic transmission do not need a transmission tunnel because the shift linkage does not usually go through the transmission tunnel. The shift linkage in automatic transmission usually goes in front of the firewall from the base of the steering column.

Tyres

A tyre is a tubular corded carcass covered with rubber or synthetic rubber, which is mounted on a wheel and inflated to provide traction for moving a vehicle and for assisting the brakes in stopping it.

Universal Joint (U-joint)

The Universal joint (U-joint) connects the drive shaft to the transmission output shaft and the differential pinion gear shaft. This joint must be flexible enough to allow changes in the driving angle (road incline) and the drive shaft. This way, the torque is constantly transmitted when the rear axle is moving up and down. Smaller U-joints are used to route the turning motion of the steering wheel through the steering column to the steering box. There are two types of U-joints, the cross and roller type and the ball and trunnion type. The cross and roller type is used the most; it allows the drive shaft to bend. The ball and trunnion type less frequently used; it allows the drive shaft to bend and also permits backward and forward motion of the drive shaft.

Vacuum Hoses and Motors

Vacuum lines are a series of hoses, or tubing, to the intake manifold. These hoses supply vacuum to various components of the engine, such as the emissions control system. Most air conditioning systems have vacuum motors to open and close the doors on the air conditioning ducts. A vacuum motor is just a small diaphragm with connecting rods to activate the valves of the system. They have the advantages of simplicity and quietness.

Vacuum Pump

Most of the fuel pumps have a vacuum booster section that operates the windshield wipers at an almost constant speed. The fuel section then functions in the same way as ordinary fuel pumps. One difference is that the rotation of the camshaft eccentric in the vacuum pump also operates the vacuum booster section by actuating the pump arm, which pushes a link and the bellows diaphragm assembly upward, expelling air in the upper chamber through its exhaust valve out into the intake manifold. On the return stroke of the pump arm, the diaphragm spring moves the bellows diaphragm down, producing a suction in the vacuum chamber. The suction opens the intake valve of the vacuum section and draws air through the inlet pipe from the windshield wipers. When the wipers are not operating, the intake manifold suction (vacuum) holds the diaphragm up against the diaphragm spring pressure so that the diaphragm does not function with every stroke of the pump arm. When the vacuum is greater than the suction produced by the pump, the airflows from the windshield wiper through the inlet valve and vacuum chamber of the pump and out the exhaust valve outlet to the manifold, leaving the vacuum section inoperative. With high suction in the intake manifold, the operation of the wiper will be the same as if the pump were not installed. When the suction is low, as when the engine is accelerated or operating at high speed, the suction of the pump is greater than that in the manifold and the vacuum section operates the wipers at a constant speed.

Valve Cover

The valve cover covers the valve train. The valve train consists of rocker arms, valve springs, push rods, lifters and cam (in an overhead cam engine). The valve cover can be removed to adjust the valves. Oil is pumped up through the pushrods and dispersed underneath the valve cover, which keeps the rocker arms lubricated. Holes are located in various places in the engine head so that the oil recirculates back down to the oil pan. For this reason, the valve cover must be oil-tight; it is often the source of oil leaks. One way to determine if your valve cover is bent is to remove the gasket and put the valve cover back on to the cylinder head. When the valve cover and cylinder head come into contact, the cover should sit flat. If it rocks, it is bent. A symptom of a bent or leaking valve cover is a pinching of the valve cover gasket. This means that the gasket is sealing one area and not sealing another area. This condition produces a leak; oil could be leaking down the side of the engine. Some valve covers are hard to access, because they are covered with other engine parts. Chronic valve cover leakage can sometimes be fixed by using two gaskets glued together instead of using just one.

Valve Lifter

The valve lifter is the unit that makes contact with the valve stem and the camshaft and rides on the camshaft. It opens the valve when the cam lobes push it upwards. The engine oil comes into the lifter body under pressure. It passes through a little opening at the bottom of an inner piston to a cavity underneath the piston. The oil forces the piston upward until it contacts the push rod. When the cam raises the valve lifter, the pressure is placed on the inner piston, which tries to push the oil back through the little opening. It can’t do this, because a small check valve seals the opening. When the cam goes upward, the lifter solidifies and lifts the valve. Then, when the cam goes down, the lifter is pushed down by the push rod. It adjusts automatically to remove clearances.

Valve Ports

Valve ports are openings in the cylinder head. Intake ports let the fuel mixture into the cylinder head, and exhaust ports let the exhaust out.

Valve Seals

The valve seal is a unit that goes over the end of the valve stem. It keeps excess oil from getting between the valve guide and the valve stem.

Valve Springs

The valve springs keep the valves closed tightly against their seats until the cam opens the valve. After the cam turns (releasing pressure), the valve springs close the valves.

Valves

The valve opens and close the valve ports. If the ports were always open, the fuel exploded in the combustion chamber would leave through the ports. The explosion has to be kept in the combustion chamber to push the piston down. The valves are set up to open and close at exactly the right moment. One lets the fuel mixture in and closes. After the fuel explodes and pushes the piston down, the other valve lets the exhaust out.

Visor

The visor is a flat sunshade and is usually movable. It is attached to the interior of the car at the top of the windshield. Visors protect the eyes of the driver and passengers from the sun’s glare.

Voltage Regulator

The voltage regulator controls voltage and current output of the alternator by automatically cutting resistance in or out of the field circuit to keep it in a safe value. Varying the resistance alters the amount of current passing through the field. When the battery becomes fully charged, the resistance is cut into the field circuit and the charging rate is decreased. In electromagnetic regulators, the voltage regulator unit limits voltage output by controlling the amount of current applied to the rotating field. The field relay on these regulators connects the alternator field windings and voltage regulator windings directly to the battery. The conventional cutout relay unit has been eliminated by the diodes in the alternator. The current regulator has also been eliminated by the current-limiting characteristic of the alternator design. Basically, in a transistorized or an electronic regulator, the transistor is switched on and off to control the alternator field current. The frequency of switching depends on the alternator speed and accessory load, with the possibility that the on-off cycle may be repeated as often as 7000 times per second. The transistorized units have a voltage limiter adjustment. The electronic units are factory calibrated and sealed. They are also nonadjustable

Water (Coolant) Jackets

Water Jackets are used in cars to keep them cool. It is a collection of passages within the block and head, which let the coolant circulate around the “hot spots” (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off. The engine block is actually manufactured in one piece with the water jackets cast into the block and cylinder head. At normal operating temperature, the water pump forces the coolant through the head gasket openings and on into the water jackets in the cylinder head. It flows around in there, cooling everything off by absorbing the heat. After doing its thing, the coolant flows through the upper hose to the radiator where it releases the heat. Then, the water pump sends it back down into the engine’s water jackets to continue the cooling process. On the sides of the engine are “freeze” or “expansion” plugs, which are sheet metal plugs pressed into a series of holes in the block, and are designed to hold the pressure of the cooling system. However, they pop out if the coolant in the block ever freezes.

Wheel (Slave) Cylinder

The wheel cylinder, also called the brake cylinder or slave cylinder, is a cylinder in which movable piston(s) convert hydraulic fluid pressure into mechanical force. The piston(s) within the cylinder move the brake shoes or pads against the braking surface of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. The cylinder is usually made up of a single-bore cylinder casting, an internal compression spring, two pistons, two rubber cups or seals, two rubber boots to prevent entry of dirt and water, and a bleeder screw (valve). In drum type brakes, the wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the toe end of each brake shoe. In disc brakes, the wheel cylinder is part of the caliper. As the brake pedal is depressed, it moves pistons within the master cylinder, forcing hydraulic brake fluid through the brake lines and into cylinders at each wheel. The fluid under pressure causes the wheel cylinders’ pistons to move, which forces the shoes or pads against the brake drums or rotors. Two-way pressure is applied when the wheel cylinder is activated. Brake fluid enters the center of the cylinder, forcing the pistons apart. Pushrods at the piston ends then apply equal pressure to the brake shoes. When pressure is released, a return spring pulls the pistons together.

Wheel Lugs

The large bolts that go through the wheel rim and secure it to the wheel hub are known as the wheel lugs. They are pressed into the hub from the inboard side so they cannot pull out when tightened. The lug nuts thread onto the wheel lugs, clamping the wheel rim between the hub and lug nuts. If the wheel lug nuts are not properly tightened your wheel will come off. Over- tightening, conversely, can prevent you from being able to change a flat tire.

Wheel Well

The wheel well is either plastic or metal. Metal wheel wells are usually part of the body shell. Metal wheel wells strengthen the structure of the car because of their shape, and because they are strongly welded to the body shell. Most rear wheel wells are made of metal. Wheel wells are coated with a rock-proof, rubberized coating underneath to prevent the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they hit. The front wheels are often made of plastic. This is because it is harder to mount the engine with the front wheel wells in place. Plastic wheel wells can be removed, and are easier to mount the engine during the manufacturing of the car.

Wheels

Wheels come in many different designs and usually fall into two categories: stamped sheet metal and machine castings. Some wheels are a combination of the two. Generally cast alloy wheels are higher priced, but have greater strength than stamped sheet metal wheels. The most common are the stamped sheet metal wheels because they are less expensive to produce and are adequate for most uses. Some cars have wire wheels, which consist of three basic components; inner rings, outer rings, and a series of spokes, which connect the two. Cast aluminum wheels are very popular, magnesium wheels are also popular. Both are popular because they are lightweight and strong.

Windshield

Most windshields are stationary. They are fixed in place with a weather-strip made of rubber, which has a groove on the inside and a groove on the outside. The inside groove holds the glass; the outside groove holds the metal rim of the windshield opening in place. The glass “floats” in a plastic sealant that is spread out between the edge of the glass and the frame of the windshield. Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it is struck during a collision. The glass sticks to the plastic to eliminate glass from flying around the interior and injuring someone.

Windshield Washers

All cars use an electric pump-operated windshield washer with a positive displacement washer pump. On some, the motor is placed in the washer reservoir, while on others, it is driven by a wiper motor. When the pump is attached to the wiper motor, the four lobe cam starts a spring-loaded follower, but the pump does not operate all the time that the wiper motor is running. This is because the pumping mechanism is locked out and pumping action occurs.

Windshield Wipers

Most cars have an intermittent wiper system, which permits the driver to select a delayed wipe that operates only every few seconds. A representative wiper/washer unit is the wiper assembly, which incorporates a depressed park system that places the wiper blades below the hood line in the parked position. The relay control uses a relay coil, relay armature, and switch assembly. It controls starting and stopping of the wiper through a latching mechanism. An electric washer pump is mounted on the gear box section of the wiper. The wiper unit gear assembly drives it.

Wires and Cables

Wires and cables conduct electricity. Usually, they are made of annealed copper and are used to carry electricity to the various electrical devices and equipment on passenger cars and trucks. Wire and cable sizes are expressed by a gauge number, which indicates the cross-sectional area of the conductor. The larger the diameter of the wire or cable, the smaller the gauge size number. Cables are made of several strands of wire. The cross-sectional area is equal to the circular mil area of a single strand times the number of strands.

Thrust Bearings

Thrust bearings are similar to ball bearings except that the plates that the balls ride between are designed as flat washers. The balls riding between these washers reduce side-to-side load. These are used inside of the transmission, rear end and many other areas of the car.

Tie Rod Ends

Tie rod ends are utilized in the steering linkage, steering knuckle pivot supports, and various other hinge mechanisms. Ball joints that join the key parts of the steering linkage pass on the steering wheel’s motion no matter what the angle of the linkage or the vibration from the road.

Timing Chain/ Belt

The automobile engine uses a metal timing chain, or a flexible toothed timing belt to rotate the camshaft. The timing chain/belt is driven by the crankshaft. The timing chain, or timing belt is used to “time” the opening and closing of the valves. The camshaft rotates once for every two rotations of the crankshaft.

Torsion Bars

Torsion bar suspension uses the flexibility of a steel bar or tube, twisting lengthwise to provide spring action. Two rods of spring steel are used in this type of suspension. One end of the bar is fixed solidly to a part of the frame behind the wheel; the other is attached to the lower control arm. As the arm rises and falls with wheel movement, the bar twists and absorbs more of the road shocks before they can reach the body of the car. Just like a spring that rebounds after it has been compressed, the bar untwists when the pressure is released. Adjusting the torsion bars controls the height of the front end of the vehicle. The adjusting bolts are located at the torsion bar anchors in the front crossmember. The inner ends of the lower control arms are bolted to the crossmember and pivot through a bushing.

Transmission Fluid Dip Stick

The transmission fluid dip stick is a long metal rod that goes into the transmission. It serves check how much transmission fluid is in the transmission. The dip stick is held in a tube; the end of the tube extends into the transmission. It has measurement markings on it. If you pull it out, you can see whether you have enough transmission fluid, or whether you need more by the level of fluid on the markings. Most manual transmissions do not have dipsticks, instead they use a filler hole which is at the same level as the correct oil level. When the oil is topped up or refilled, the mechanic simply adds oil until the filler hole’s level is reached.

Transmission Gears

Most cars have from three to five forward gears, and one reverse gear. The transmission changes the ratio of the engine speed and the wheels by connecting gears in various combinations. First gear connects the engine power to the drive wheels via a pair of reduction gear sets, which gives increased power and reduced wheelspeed when the car is beginning to move. Gears work exactly like levers. A small gear driving a larger one gives an increase in torque, and a decrease in speed, and vise-versa. Transmission gears are heat-treated, high quality steel. They have smooth, hard teeth, cut on precision machinery while red hot. There are many types of gear teeth, but most transmissions use spur and helical gears. Most of the gears are the helical type, because they last longer and are more quiet than spur gears. There has to be enough room (a few thousandths of an inch) between the gear teeth for lubrication, expansion, and any irregularities in size.

Transmission tunnel

The transmission tunnel is a cone-shaped formation in the front of the floor pan. Its shape duplicates the transmission, but it is a little bit bigger and provides about two inches of clearance around the transmission. The transmission tunnel does not exist in front wheel drive cars, because the transmission is on the side of the engine completely under the hood. Only rear-wheel drive cars have transmission tunnels. A manual transmission tunnel has a hole in it to allow the shift linkage to be worked from inside the car. The shifter linkage goes through the transmission tunnel. A rubber boot on the shifter linkage stops dirt, dust and exhaust fumes from entering the passenger compartment. The rubber boot is mounted onto the transmission tunnel and fastened securely around the gearshift linkage. Vehicles with automatic transmission do not need a transmission tunnel because the shift linkage does not usually go through the transmission tunnel. The shift linkage in automatic transmission usually goes in front of the firewall from the base of the steering column.

Tyres

A tyre is a tubular corded carcass covered with rubber or synthetic rubber, which is mounted on a wheel and inflated to provide traction for moving a vehicle and for assisting the brakes in stopping it.

Universal Joint (U-joint)

The Universal joint (U-joint) connects the drive shaft to the transmission output shaft and the differential pinion gear shaft. This joint must be flexible enough to allow changes in the driving angle (road incline) and the drive shaft. This way, the torque is constantly transmitted when the rear axle is moving up and down. Smaller U-joints are used to route the turning motion of the steering wheel through the steering column to the steering box. There are two types of U-joints, the cross and roller type and the ball and trunnion type. The cross and roller type is used the most; it allows the drive shaft to bend. The ball and trunnion type less frequently used; it allows the drive shaft to bend and also permits backward and forward motion of the drive shaft.

Vacuum Hoses and Motors

Vacuum lines are a series of hoses, or tubing, to the intake manifold. These hoses supply vacuum to various components of the engine, such as the emissions control system. Most air conditioning systems have vacuum motors to open and close the doors on the air conditioning ducts. A vacuum motor is just a small diaphragm with connecting rods to activate the valves of the system. They have the advantages of simplicity and quietness.

Vacuum Pump

Most of the fuel pumps have a vacuum booster section that operates the windshield wipers at an almost constant speed. The fuel section then functions in the same way as ordinary fuel pumps. One difference is that the rotation of the camshaft eccentric in the vacuum pump also operates the vacuum booster section by actuating the pump arm, which pushes a link and the bellows diaphragm assembly upward, expelling air in the upper chamber through its exhaust valve out into the intake manifold. On the return stroke of the pump arm, the diaphragm spring moves the bellows diaphragm down, producing a suction in the vacuum chamber. The suction opens the intake valve of the vacuum section and draws air through the inlet pipe from the windshield wipers. When the wipers are not operating, the intake manifold suction (vacuum) holds the diaphragm up against the diaphragm spring pressure so that the diaphragm does not function with every stroke of the pump arm. When the vacuum is greater than the suction produced by the pump, the airflows from the windshield wiper through the inlet valve and vacuum chamber of the pump and out the exhaust valve outlet to the manifold, leaving the vacuum section inoperative. With high suction in the intake manifold, the operation of the wiper will be the same as if the pump were not installed. When the suction is low, as when the engine is accelerated or operating at high speed, the suction of the pump is greater than that in the manifold and the vacuum section operates the wipers at a constant speed.

Valve Cover

The valve cover covers the valve train. The valve train consists of rocker arms, valve springs, push rods, lifters and cam (in an overhead cam engine). The valve cover can be removed to adjust the valves. Oil is pumped up through the pushrods and dispersed underneath the valve cover, which keeps the rocker arms lubricated. Holes are located in various places in the engine head so that the oil recirculates back down to the oil pan. For this reason, the valve cover must be oil-tight; it is often the source of oil leaks. One way to determine if your valve cover is bent is to remove the gasket and put the valve cover back on to the cylinder head. When the valve cover and cylinder head come into contact, the cover should sit flat. If it rocks, it is bent. A symptom of a bent or leaking valve cover is a pinching of the valve cover gasket. This means that the gasket is sealing one area and not sealing another area. This condition produces a leak; oil could be leaking down the side of the engine. Some valve covers are hard to access, because they are covered with other engine parts. Chronic valve cover leakage can sometimes be fixed by using two gaskets glued together instead of using just one.

Valve Lifter

The valve lifter is the unit that makes contact with the valve stem and the camshaft and rides on the camshaft. It opens the valve when the cam lobes push it upwards. The engine oil comes into the lifter body under pressure. It passes through a little opening at the bottom of an inner piston to a cavity underneath the piston. The oil forces the piston upward until it contacts the push rod. When the cam raises the valve lifter, the pressure is placed on the inner piston, which tries to push the oil back through the little opening. It can’t do this, because a small check valve seals the opening. When the cam goes upward, the lifter solidifies and lifts the valve. Then, when the cam goes down, the lifter is pushed down by the push rod. It adjusts automatically to remove clearances.

Valve Ports

Valve ports are openings in the cylinder head. Intake ports let the fuel mixture into the cylinder head, and exhaust ports let the exhaust out.

Valve Seals

The valve seal is a unit that goes over the end of the valve stem. It keeps excess oil from getting between the valve guide and the valve stem.

Valve Springs

The valve springs keep the valves closed tightly against their seats until the cam opens the valve. After the cam turns (releasing pressure), the valve springs close the valves.

Valves

The valve opens and close the valve ports. If the ports were always open, the fuel exploded in the combustion chamber would leave through the ports. The explosion has to be kept in the combustion chamber to push the piston down. The valves are set up to open and close at exactly the right moment. One lets the fuel mixture in and closes. After the fuel explodes and pushes the piston down, the other valve lets the exhaust out.

Visor

The visor is a flat sunshade and is usually movable. It is attached to the interior of the car at the top of the windshield. Visors protect the eyes of the driver and passengers from the sun’s glare.

Voltage Regulator

The voltage regulator controls voltage and current output of the alternator by automatically cutting resistance in or out of the field circuit to keep it in a safe value. Varying the resistance alters the amount of current passing through the field. When the battery becomes fully charged, the resistance is cut into the field circuit and the charging rate is decreased. In electromagnetic regulators, the voltage regulator unit limits voltage output by controlling the amount of current applied to the rotating field. The field relay on these regulators connects the alternator field windings and voltage regulator windings directly to the battery. The conventional cutout relay unit has been eliminated by the diodes in the alternator. The current regulator has also been eliminated by the current-limiting characteristic of the alternator design. Basically, in a transistorized or an electronic regulator, the transistor is switched on and off to control the alternator field current. The frequency of switching depends on the alternator speed and accessory load, with the possibility that the on-off cycle may be repeated as often as 7000 times per second. The transistorized units have a voltage limiter adjustment. The electronic units are factory calibrated and sealed. They are also nonadjustable

Water (Coolant) Jackets

Water Jackets are used in cars to keep them cool. It is a collection of passages within the block and head, which let the coolant circulate around the “hot spots” (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off. The engine block is actually manufactured in one piece with the water jackets cast into the block and cylinder head. At normal operating temperature, the water pump forces the coolant through the head gasket openings and on into the water jackets in the cylinder head. It flows around in there, cooling everything off by absorbing the heat. After doing its thing, the coolant flows through the upper hose to the radiator where it releases the heat. Then, the water pump sends it back down into the engine’s water jackets to continue the cooling process. On the sides of the engine are “freeze” or “expansion” plugs, which are sheet metal plugs pressed into a series of holes in the block, and are designed to hold the pressure of the cooling system. However, they pop out if the coolant in the block ever freezes.

Wheel (Slave) Cylinder

The wheel cylinder, also called the brake cylinder or slave cylinder, is a cylinder in which movable piston(s) convert hydraulic fluid pressure into mechanical force. The piston(s) within the cylinder move the brake shoes or pads against the braking surface of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. The cylinder is usually made up of a single-bore cylinder casting, an internal compression spring, two pistons, two rubber cups or seals, two rubber boots to prevent entry of dirt and water, and a bleeder screw (valve). In drum type brakes, the wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the toe end of each brake shoe. In disc brakes, the wheel cylinder is part of the caliper. As the brake pedal is depressed, it moves pistons within the master cylinder, forcing hydraulic brake fluid through the brake lines and into cylinders at each wheel. The fluid under pressure causes the wheel cylinders’ pistons to move, which forces the shoes or pads against the brake drums or rotors. Two-way pressure is applied when the wheel cylinder is activated. Brake fluid enters the center of the cylinder, forcing the pistons apart. Pushrods at the piston ends then apply equal pressure to the brake shoes. When pressure is released, a return spring pulls the pistons together.

Wheel Lugs

The large bolts that go through the wheel rim and secure it to the wheel hub are known as the wheel lugs. They are pressed into the hub from the inboard side so they cannot pull out when tightened. The lug nuts thread onto the wheel lugs, clamping the wheel rim between the hub and lug nuts. If the wheel lug nuts are not properly tightened your wheel will come off. Over- tightening, conversely, can prevent you from being able to change a flat tire.

Wheel Well

The wheel well is either plastic or metal. Metal wheel wells are usually part of the body shell. Metal wheel wells strengthen the structure of the car because of their shape, and because they are strongly welded to the body shell. Most rear wheel wells are made of metal. Wheel wells are coated with a rock-proof, rubberized coating underneath to prevent the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they hit. The front wheels are often made of plastic. This is because it is harder to mount the engine with the front wheel wells in place. Plastic wheel wells can be removed, and are easier to mount the engine during the manufacturing of the car.

Wheels

Wheels come in many different designs and usually fall into two categories: stamped sheet metal and machine castings. Some wheels are a combination of the two. Generally cast alloy wheels are higher priced, but have greater strength than stamped sheet metal wheels. The most common are the stamped sheet metal wheels because they are less expensive to produce and are adequate for most uses. Some cars have wire wheels, which consist of three basic components; inner rings, outer rings, and a series of spokes, which connect the two. Cast aluminum wheels are very popular, magnesium wheels are also popular. Both are popular because they are lightweight and strong.

Windshield

Most windshields are stationary. They are fixed in place with a weather-strip made of rubber, which has a groove on the inside and a groove on the outside. The inside groove holds the glass; the outside groove holds the metal rim of the windshield opening in place. The glass “floats” in a plastic sealant that is spread out between the edge of the glass and the frame of the windshield. Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it is struck during a collision. The glass sticks to the plastic to eliminate glass from flying around the interior and injuring someone.

Windshield Washers

All cars use an electric pump-operated windshield washer with a positive displacement washer pump. On some, the motor is placed in the washer reservoir, while on others, it is driven by a wiper motor. When the pump is attached to the wiper motor, the four lobe cam starts a spring-loaded follower, but the pump does not operate all the time that the wiper motor is running. This is because the pumping mechanism is locked out and pumping action occurs.

Windshield Wipers

Most cars have an intermittent wiper system, which permits the driver to select a delayed wipe that operates only every few seconds. A representative wiper/washer unit is the wiper assembly, which incorporates a depressed park system that places the wiper blades below the hood line in the parked position. The relay control uses a relay coil, relay armature, and switch assembly. It controls starting and stopping of the wiper through a latching mechanism. An electric washer pump is mounted on the gear box section of the wiper. The wiper unit gear assembly drives it.

Wires and Cables

Wires and cables conduct electricity. Usually, they are made of annealed copper and are used to carry electricity to the various electrical devices and equipment on passenger cars and trucks. Wire and cable sizes are expressed by a gauge number, which indicates the cross-sectional area of the conductor. The larger the diameter of the wire or cable, the smaller the gauge size number. Cables are made of several strands of wire. The cross-sectional area is equal to the circular mil area of a single strand times the number of strands.

USEFUL TERMINOLOGY IN AUTOMOBILE INDUSTRY

A

ABBREVIATIONS

brake horsepower, bhp. – horsepower, hp.- kilometers per hour, kph. – miles per hour, mph. -

cubic centimeter, cc – millimeter, mm. – overhead camshaft, OHC – overhead valve, OHV -

revolutions per minute, rpm. – cubic inch, cu. in.

AERODYNAMICS

The study of the behavior of the airflow as it passes around a moving object and the forces

exerted by the air on the object. In car design the positive and negative lift of the airflow is

studied in wind tunnels. Negative lift is preferred to press the vehicle closer to the ground.

Car air resistance is also studied.

AUTOMATIC TRANSMISSION

A transmission that shifts its own gears according to the prevailing speed, load, and road

condition. Also called automatic gearbox. Operation can be electrical or hydraulic.

B

BELT DRIVE

A system where the final drive from gearbox to wheels is by leather or rubber belts that are

contained on pulleys. Today many of the engine-driven auxiliaries use belt drives.

BERLINE

From World War I, it described a closed luxury car with small windows, which allowed the

occupants to see out but to be barely seen from the outside.

BORE

The diameter of a gasoline or steam reciprocating engine cylinder. The displacement can be

increased by increasing the diameter (reboring).

BRAKE HORSEPOWER (bhp.)

The measure of an engine’s horsepower without the loss in power caused by the gearbox,

generator, differential, water pump and other auxiliaries. The actual horsepower delivered

to the driving wheels is less.

C

CABRIOLET

A description of an auto with collapsible top (convertible) and seating two or four

passengers. Also called a drophead coupé.

CAM

An eccentric (off-center) lobe or projection on a rotating shaft; used to transmit a motion at

a predetermined time during the rotation of the shaft.

CAMSHAFT

A rotating shaft with a number of cams or eccentric lobes used to operate the engine valves,

usually via pushrods and rocker arms.

CARBURETOR

A device through which air and fuel are atomized and drawn into the engine. It meters the

proper proportions of fuel and air to form a combustible mixture and varies the ratio

according to the engine operation.

CHAIN DRIVE

The driving of one shaft by another by means of a toothed wheel on each shaft, with the

wheels connected by an endless chain with special links engaging the teeth.

CHASSIS

The basic-strength auto frame including the engine, suspension, wheels, brakes and drive

train. A car without its body or coachwork. In monocoque or unit construction it is integral

with the body.

CHOKE

A temporary restriction in a carburetor throat that reduces the flow of air and enriches the

fuel-air mixture to aid in starting the engine.

CLUTCH

A friction device used to connect the engine to the drive train. Used when changing gear

ratios during acceleration. Can connect or disconnect the engine and the drive train at

driver’s will.

COACHWORK (French Carrosserie, German Karosserie, Italian Carrozzeria)

The automobile body: especially the comfort and luxury appointments as distinguished from

the operational chassis.

COMBUSTION CHAMBER

The space remaining at the top of the cylinder when the piston is at the top dead center

position. Where the fuel-air mixture begins to burn.

COMPRESSION

In internal-combustion reciprocating engines, the squeezing of the fuel-air mixture in the

cylinder of a spark-ignition engine or the squeezing of the air in a diesel engine.

Compression makes combustion more effective and increases engine efficiency.

COMPRESSION RATIO

The ratio of the cylinder volume with the piston at bottom dead center to the cylinder volume

with the piston at top dead center.

CONNECTING ROD

The arm that connects the piston to the crankshaft and converts the reciprocating motion

into rotary motion.

CONVERTIBLE

Any car with a folding roof. Term used in U.S. since the 1930s. In the 1950s, the “hardtop

convertible” was developed to look like a convertible but had a fixed roof that did not fold.

Also called a drophead coupé.

CONVERTIBLE SEDAN

The conventional body has 4 doors and a folding top with roll-up windows.

COUPÉ

Originally meant a vehicle “cut” by a glass partition behind the front seats that enabled the

rear passengers to ride enclosed and the driver exposed. Today, a two-to-five-seater with

smaller interior than a sedan. Usually a sporty type.

COWL

That part of a car’s body between the engine compartment and the driver.

CRANKCASE

A pan or box that encloses the bottom of the engine, supports the crankshaft, and contains

the oil for the engine.

CRANKSHAFT

The main shaft of an engine with a U-shaped offset at each cylinder to which the connecting

rod is attached. It delivers rotary motion taken from the reciprocating pistons and connecting

rods.

CUBIC CAPACITY

The volume of the cylinder between the piston top dead center and bottom dead center.

Expressed in cubic centimeters or cubic inches.

CUBIC CENTIMETER (cc)

European, metric, and competition measure of engine displacement: 1,000 cc = 1 liter,

which equals about 61 cubic inches.

CUBIC INCH (cu. in.)

U.S. measure of engine displacement: 1 cubic inch = 16.387 cc.

CUSTOM CAR

An automobile that has been restyled, or an all-new body fitted on an existing chassis.

CYCLE-CAR

A term used to describe the very light production autos made prior to 1922. Usually made

from motorcycle parts and generally powered by single- or twin-cylinder engines.

Disappeared when genuine light cars appeared.

CYLINDER

The hollow tubular cavity in the cylinder block in which the piston travels and in which

combustion takes place.

CYLINDER HEAD

The detachable part of the top of the cylinder block that contains the spark plugs and valves.

It seals the cylinder and forms the top of the combustion chamber.

D

DE DION AXLE

The nineteenth-century axle principle of Count de Dion. The wheels tied by a transverse

tube curved to clear the final drive unit rigidly mounted to the car’s chassis frame. Drive to

the wheels is by universally jointed half shafts. The tube moves vertically on a slide to allow

the wheels to rise and fall independently. General use was dropped in 1914, but still is used

on many sports and racing cars.

DIESEL ENGINE

An internal-combustion engine in which the fuel is injected into the cylinder near the end of

the compression stroke and is ignited by the heat of the compressed air in the cylinder. No

spark plug or carburetor is needed.

DIFFERENTIAL GEARS

The gears that convey engine power to the driving axles and are arranged so as to permit

the rear wheels to turn at different speeds as required when the vehicle is negotiating a

turn.

DISC BRAKE

A type of brake in which two friction pads grip a steel disc that is attached to the wheel, with

one pad on each side. Used on race cars, sports cars, and better passenger cars.

DISTRIBUTOR

The moving part of the internal-combustion engine ignition system that directs the highvoltage

current from the coil to the spark plugs in the proper firing order.

DOS-A-DOS

A four-seater auto in which four passengers face each other or sit back-to-back. Seldom

seen after the early 1900s.

DREAM CAR

A one-of-a-kind futuristic, experimental automobile usually appearing at auto shows to

stimulate interest in the manufacturer’s products. Much design benefit spurs from dream

cars and many reach the production stage.

DRIVE TRAIN

A combination of gears, clutches, shafts, etc., that transmits the engine power to the wheels.

DROPHEAD COUPE

See Convertible. Also called cabriolet on the Continent.

DRY SUMP

Type of internal-combustion engine in which the lubricating oil is stored either in a separate

tank or cooling radiator instead of in the crankcase pan. The oil is pumped to and taken from

the engine by separate pumps.

E

ELECTRICAL SYSTEM

In electric ignition internal-combustion engines, those components required to convert the

electricity produced by the generator into a high-voltage spark for the plugs. Includes:

generator or alternator, points, condenser, coil, distributor and spark plugs plus wiring.

ENGINE TYPES

F-Head Side exhaust valve and overhead inlet valve.

L-Head Both valves on one side of the cylinder.

T-Head Exhaust valve on one side and inlet valve on the other side of the cylinder. (Twincamshafts).

I-Head Both valves located directly over the piston. Also called valve–in-head or overhead

valve engine.

SOHC Single overhead camshaft.

DOHC Double overhead camshafts.

HEMI and HEMI-HEAD (See listings in Glossary.)

EPICYCLIC GEARBOX

A form of gear used by Benz in which small pinions revolve around a central or sun gear

and mesh with an outer ring gear called the annulus. Type used in the Ford Model T. Also

called planetary gears, sun-and-planet gears.

EXHAUST

The system of exhausting the burned gases from an internal-combustion engine consisting

of piping or tubing, silencers, and, at times, resonators.

F

FASTBACK

A car that has an unbroken curved line from the top of the roof to the rear bumper as

opposed to a drop in the line for a near-vertical rear window. In a fastback design the rear

window slope follows the unbroken roofline and is often at less than a 45-degree angle.

FIBERGLASS

A very tough and durable plastic material with fibers running through the plastic. Used for

race car bodies, many sports car bodies, and also enjoys considerable acceptance for

passenger car bodies.

FLYWHEEL

A large, heavy iron or steel disc attached to the rear of an engine crankshaft in order to

provide sufficient centrifugal force to smooth the power impulses from the cylinders.

FOUR-STROKE CYCLE

An internal-combustion engine that requires two revolutions per cylinder or four piston

strokes to achieve a power stroke: internal stroke, compression stroke, power stroke,

exhaust stroke. More efficient than the two-stroke-cycle engine. Also called Otto cycle.

FRAME

A bridge-like, structural base of a car that supports and positions the body and major

mechanical items.

FUEL INJECTION

On internal-combustion engines, a system that injects a precisely measured amount of fuel

into the cylinder at exactly the right moment. Dispenses with the carburetor and increases

engine efficiency.

G

GAS TURBINE

An internal-combustion rotating engine with one main moving part: the rotor with pinwheellike

blades attached. Air is compressed by the first rows of blades and delivered to the

combustion chambers, from which the exhaust is directed to pass the remaining blades and

to generate the power. Power is extremely smooth due to the absence of explosions and

reciprocating parts.

GEARS

Wheels with meshing teeth to transmit power between rotating shafts. When the gear

wheels are of different sizes, a change in speed ratio occurs. Gears are made of hard steel.

G.T. / GRAND TOURING

From the Italian Gran Turismo. A car combining sedan and sports car features in which

engineering is the dominant feature. Combines excellent road handling qualities with relative

comfort. Made in two- and four-seaters with the rear seats always cramped.

H

HALF SHAFT

A rotating shaft that transmits power from the final drive unit (differential) to a power wheel.

Used in independent rear suspension and front-wheel drive. Two are required; one for each

side.

HAND CRANK

A crank handle for manually starting internal combustion engines. Used till about 1930.

Now obsolete.

HELICAL GEAR

A gear in which the teeth are cut at an angle to the shaft. The advantage is that there are

usually two teeth meshing at all times, making for smoother and quieter operation.

HEMI

Slang term for an engine with hemispherical combustion chambers, which allow for larger

and less shrouded valves. Used in many sports and racing cars.

HEMI-HEAD

A hemispherically shaped combustion chamber at the top of the engine cylinder. The

hemispheric shape provides improved efficiency because the forces of the explosion are

directed to the piston by the curved surface of the combustion chamber.

HOOD

The removable or lift-up part of an auto body that covers the engine and allows access to it.

(Bonnet in U.K.)

HORSEPOWER (hp.)

The unit for measuring the power output of an engine. One horsepower is defined as lifting

33,000 pounds one foot per minute.

HOT ROD

A production auto that has been modified by the owner for outstanding speed and

acceleration through extensive changes to the engine, chassis, and body.

HYDRAULIC

A mechanical operation based on incompressibility of liquids, generally oil and sometimes

water, and their ability to offer resistance when being forced into a small cylinder or through

an orifice, thereby transmitting an increase in applied force. Hydraulic brakes and clutches

use this principle.

HYDRAULIC VALVE LIFTER

Valve lifter using hydraulic oil pressure to operate and capable of maintaining zero

clearance between metal parts. Thus, valve noise and wear are considerably reduced, as

are the periodic valve adjustments.

HYPOID GEARS

A type of differential final drive using a spiral bevel gear on the drive shaft, allowing it to be

located below the center of the ring gear on the axle. This makes possible a lower floor in

the car.

I

INDEPENDENT SUSPENSION

Suspension in which each wheel is sprung individually so that any disturbance on the wheel

has no effect on the opposite wheel.

INLINE ENGINE

An engine having the cylinders in a straight line, one after the other. Also called a “straight”

engine.

INTERNAL-COMBUSTION ENGINE

Any engine, either reciprocating or rotary, in which the fuel is consumed in the interior of the

engine rather than outside of the engine.

J

K

KAMM BACK

Named for the German aerodynamicist W. Kamm who discovered that drag begins to

increase after the rear of a car’s cross-sectional area is reduced to 50 percent of the car’s

maximum cross section.

KNOCK-OFF

A single wing nut for fastening a wheel to the hub. Easily removed and replaced, it is struck

(knocked off) with a mallet on the wings.

L

LACQUER

A fast-drying pyroxylin paint often used to finish automobile bodies.

LAMINATED WINDSHIELD

A windshield consisting of a thin layer of rubbery plastic sandwiched between two sheets of

glass. When struck by the head in an accident, it bows out without puncturing, and the

plastic holds the glass to prevent it from splintering.

LEAF SPRINGS

A number of slightly curved, flexible steel plates of varying lengths, mounted one atop the

other. The ends are attached to the chassis, and the middle is fixed to the axle. Also called

semi-elliptic springs.

LIMITED SLIP DIFFERENTIAL

A differential that uses cone or disc clutches to lock the two separate axle shafts. This

forces both driving wheels to transmit the same drive torque regardless of the traction

available. It still allows differential action under normal driving conditions but improves

traction in mud and snow.

LIMOUSINE

A closed, chauffeur-driven automobile in which the driver is separated from the passengers

by a glass partition.

LIVE AXLE

An axle that transmits power either by separate half shafts or by side chains, as opposed to

a dead axle.

LOUVER

A slatted air intake or air outlet. Slats used to capture and control the airflow.

LUXURY CAR

A well-appointed, well-equipped, well-designed and constructed auto varying in size from a

compact to a large sedan.

M

MANUAL TRANSMISSION

A mechanism in the drive train with gears to vary the power and torque delivered to the

driven wheels. It consists of a lever that the driver operates in conjunction with the clutch to

change from one gear to another.

MOCK-UP

A full-size dummy of a car made of wood and clay, used for design studies.

N

NORMALLY ASPIRATED

An engine that intakes air or “breathes” without the assistance of a supercharger or

turbocharger.

O

OIL PUMP

An engine-driven pump that delivers oil, under pressure, to the engine’s moving parts.

OIL RING

The lowermost piston ring that scrapes off excess oil from the cylinder walls and returns it to

the oil pan via vents in the ring and piston.

OTTO CYCLE

See Four-Stroke Cycle.

OVERDRIVE

A small auxiliary gearbox that provides an additional gear ratio. It causes the drive shaft to

turn faster than the engine crankshaft or “overdrive” it. It is engaged manually when under

way and reduces fuel consumption.

OVERHEAD VALVE

See Engine Types, I-Head.

P

PHAETON

The conventional body has 4 doors with convertible top and side curtains rather than roll-up

windows. The four- seater was called a double phaeton, and the six- or seven- seater a

triple phaeton.

PINION

A small diameter gear with a small number of teeth designed to mesh with a much larger

gear wheel or a toothed rod (rack). Used in rack-and-pinion steering and for speed reduction

with an increase in power.

PISTON

A partly hollow, cylindrical metal engine part that is closed at one end and fits into the

engine cylinder. Connected to the crankshaft via the connecting rod and usually fitted with

rings to seal it in the cylinder.

PNEUMATIC TIRE

A circular tube of rubber or synthetic rubber and fabric, and sometimes also steel, attached

to the rim of the car’s wheel, having resilience due to its containing air under pressure.

PRE-SELECTOR GEARBOX

An arrangement that enables the driver to select a gear speed before he needs it and then

depress the clutch pedal when he desires to use the selected gear.

PROTOTYPE

The test model of a new car design that is intended to be produced in quantity.

PUSHROD

A metal rod connecting the valve lifter or camshaft with the valve rocker arm on overheadvalve

engines.

Q

QUADRICYCLE

An early type of light, four-wheeled automobile using bicycle wheels and a frame of steel

tubes.

R

RACK-AND-PINION STEERING

A steering system having a pinion gear at the lower end of the steering column that engages

a rack or a toothed rod that connects to the wheel steering arms.

RADIAL PLY

A tire in which the fabric cords run radially in a line from the wheel hub or straight out from

the bead or around the tubular shape of the tire. Annular belts of fabric or steel mesh add

rigidity. Advantages of this design are: more flexible side walls with a relatively stiff tread

area and a larger and more consistent footprint on the road under all driving conditions.

RECIPROCATING

Motion of an object between two limiting positions. Applied to piston engines because of the

limited up and down motion of the pistons.

RING GEAR

One of the gears in the rear axle that transmits power to the differential from the drive shaft.

ROADSTER

A description of a two-seater open car of sporty appearance with side curtains, instead of

roll-up windows.

ROCKER ARM

A pivoted lever that transmits the action of the pushrod to the valve stem. (Pushrod upward

action is converted to downward push on the valve stem.)

RUNABOUT

An open sporting-type vehicle, lightweight, with two seats and with simple bodywork.

RUNNING BOARD

A long flat board under the car doors that acts as a footstep for the passengers.

S

S.A.E. Society of Automotive Engineers.

A group known for publishing research papers and defining various standards of

measurement.

SEALED BEAM

A one-piece, hermetically sealed headlight in which the filament is an integral part of the

unit, and the lens itself is the bulb.

SEDAN

A closed car for four or more passengers with either two or four doors. (Called saloon in

U.K.)

SELECTIVE TRANSMISSION

The conventional manual transmission of today in which any gear may be selected at will as

opposed to the very early progressive transmission in which the gears had to be selected in

order.

SHOCK ABSORBERS

A term used for what are really dampers. Fittings used to absorb the energy that the wheels

convey to the springs. The dampers keep the springs from continuously rebounding. The

majority of shock absorbers are hydraulic.

SLEEVE VALVE

Consists of metal sleeves located between the piston and cylinder wall. When moved up

and down, holes in the sleeves coincide with inlet and exhaust parts to provide passage for

the gases at the right time.

SPARK PLUG

A device inserted into the combustion chamber of a cylinder on an internal-combustion

engine that provides the electrical gap across which the high-tension voltage jumps. This

creates a spark that ignites the compressed fuel-air mixture.

SPORTS CAR

An agile vehicle that is easily maneuverable, accelerates briskly, brakes positively, handles

well and steers precisely. It is tightly sprung and does not wallow and heave as does a

conventional passenger car and is therefore not as comfortable.

SPYDER or SPIDER

In the early 1900s, a light two-seater car. In the 1950s the word was revived by some Italian

manufacturers for an open two-seater sports car.

STROKE

The back-and-forth motion of the piston. The length of the motion of the piston from top

dead center to bottom dead center.

SUPERCHARGER

An air compressor fitted to an internal combustion engine to force the fuel-air mixture into

the cylinders at a pressure greater than that of the atmosphere. Boosts the power of the

engine.

SUSPENSION

The assembly of springs, shock absorbers, torsion bars, joints, arms, etc., that cushions the

shock of bumps on the road and serves to keep the wheels in constant contact with the

road, thereby improving control and traction.

SWING AXLE

Type of independent rear suspension using half shafts that have universal joints only at their

inboard ends on both sides of the differential. This causes a camber angle change of the

wheel with up-and-down wheel movements.

T

TACHOMETER

An instrument that indicates the number of revolutions per minute at which the engine is

turning.

TORPEDO

An open sports vehicle generally with an unbroken design line from the hood to the back of

the car.

TORSION BAR

A rod in the suspension system that, when twisted from a grip at one end, functions like a

spring.

TOURING CAR (British-TOURER)

An open car with seats for four or more passengers. Early models had no side weather

protection but later were fitted with detachable side screens and curtains. Made until about

1930.

TRANSMISSION

The gear-changing or gear-shifting system through which engine power is transferred to the

wheels. The purpose of gear changing is to keep maximum engine power applied to the

wheels at all times for all conditions, from start-up to high speeds.

TREAD

Width of a car measured from the center line of the wheels. Sometimes called the track.

Also the pattern on the surface of a tire.

TRICYCLE

A three-wheeled, early-type open automobile using bicycle wheels and a steel-tube frame.

TURBOCHARGER

A supercharging device driven by exhaust gases from the engine.

TWO-STROKE CYCLE

An internal-combustion engine that requires only one revolution per cylinder or two piston

strokes (up and down) to achieve a power stroke. Rarely used in automobiles.

U

V

VALVE

Device that opens and closes the combustion chamber of an internal-combustion engine to

admit the fuel-air mixture or exhaust the gases.

VALVE-IN-HEAD

See Engine Types, I-Head.

VEE ENGINE

An engine with cylinders arranged in two rows at an angle to the common crankshaft. Has a

“V” shape when viewed from the front.

VIS-A-VIS

A four-seater in which two passengers faced the driver. Used around the turn of the century.

VOITURE LEGERE

A light car, especially a racing car falling between the heavy cars and the voiturette. Term

seldom used to describe production cars. Not used after 1914.

VOITURETTE

Early two-seater touring car. Name first used by Leon Bollee and then applied to any small

car.

W

WHEELBASE

The distance between the centers of the front and rear wheel axles as viewed from the side

of the car.

USEFUL TERMINOLOGY IN AUTOMOBILE

USEFUL TERMINOLOGY IN AUTOMOBILE INDUSTRY

A

ABBREVIATIONS

brake horsepower, bhp. – horsepower, hp.- kilometers per hour, kph. – miles per hour, mph. -

cubic centimeter, cc – millimeter, mm. – overhead camshaft, OHC – overhead valve, OHV -

revolutions per minute, rpm. – cubic inch, cu. in.

AERODYNAMICS

The study of the behavior of the airflow as it passes around a moving object and the forces

exerted by the air on the object. In car design the positive and negative lift of the airflow is

studied in wind tunnels. Negative lift is preferred to press the vehicle closer to the ground.

Car air resistance is also studied.

AUTOMATIC TRANSMISSION

A transmission that shifts its own gears according to the prevailing speed, load, and road

condition. Also called automatic gearbox. Operation can be electrical or hydraulic.

B

BELT DRIVE

A system where the final drive from gearbox to wheels is by leather or rubber belts that are

contained on pulleys. Today many of the engine-driven auxiliaries use belt drives.

BERLINE

From World War I, it described a closed luxury car with small windows, which allowed the

occupants to see out but to be barely seen from the outside.

BORE

The diameter of a gasoline or steam reciprocating engine cylinder. The displacement can be

increased by increasing the diameter (reboring).

BRAKE HORSEPOWER (bhp.)

The measure of an engine’s horsepower without the loss in power caused by the gearbox,

generator, differential, water pump and other auxiliaries. The actual horsepower delivered

to the driving wheels is less.

C

CABRIOLET

A description of an auto with collapsible top (convertible) and seating two or four

passengers. Also called a drophead coupé.

CAM

An eccentric (off-center) lobe or projection on a rotating shaft; used to transmit a motion at

a predetermined time during the rotation of the shaft.

CAMSHAFT

A rotating shaft with a number of cams or eccentric lobes used to operate the engine valves,

usually via pushrods and rocker arms.

CARBURETOR

A device through which air and fuel are atomized and drawn into the engine. It meters the

proper proportions of fuel and air to form a combustible mixture and varies the ratio

according to the engine operation.

CHAIN DRIVE

The driving of one shaft by another by means of a toothed wheel on each shaft, with the

wheels connected by an endless chain with special links engaging the teeth.

CHASSIS

The basic-strength auto frame including the engine, suspension, wheels, brakes and drive

train. A car without its body or coachwork. In monocoque or unit construction it is integral

with the body.

CHOKE

A temporary restriction in a carburetor throat that reduces the flow of air and enriches the

fuel-air mixture to aid in starting the engine.

CLUTCH

A friction device used to connect the engine to the drive train. Used when changing gear

ratios during acceleration. Can connect or disconnect the engine and the drive train at

driver’s will.

COACHWORK (French Carrosserie, German Karosserie, Italian Carrozzeria)

The automobile body: especially the comfort and luxury appointments as distinguished from

the operational chassis.

COMBUSTION CHAMBER

The space remaining at the top of the cylinder when the piston is at the top dead center

position. Where the fuel-air mixture begins to burn.

COMPRESSION

In internal-combustion reciprocating engines, the squeezing of the fuel-air mixture in the

cylinder of a spark-ignition engine or the squeezing of the air in a diesel engine.

Compression makes combustion more effective and increases engine efficiency.

COMPRESSION RATIO

The ratio of the cylinder volume with the piston at bottom dead center to the cylinder volume

with the piston at top dead center.

CONNECTING ROD

The arm that connects the piston to the crankshaft and converts the reciprocating motion

into rotary motion.

CONVERTIBLE

Any car with a folding roof. Term used in U.S. since the 1930s. In the 1950s, the “hardtop

convertible” was developed to look like a convertible but had a fixed roof that did not fold.

Also called a drophead coupé.

CONVERTIBLE SEDAN

The conventional body has 4 doors and a folding top with roll-up windows.

COUPÉ

Originally meant a vehicle “cut” by a glass partition behind the front seats that enabled the

rear passengers to ride enclosed and the driver exposed. Today, a two-to-five-seater with

smaller interior than a sedan. Usually a sporty type.

COWL

That part of a car’s body between the engine compartment and the driver.

CRANKCASE

A pan or box that encloses the bottom of the engine, supports the crankshaft, and contains

the oil for the engine.

CRANKSHAFT

The main shaft of an engine with a U-shaped offset at each cylinder to which the connecting

rod is attached. It delivers rotary motion taken from the reciprocating pistons and connecting

rods.

CUBIC CAPACITY

The volume of the cylinder between the piston top dead center and bottom dead center.

Expressed in cubic centimeters or cubic inches.

CUBIC CENTIMETER (cc)

European, metric, and competition measure of engine displacement: 1,000 cc = 1 liter,

which equals about 61 cubic inches.

CUBIC INCH (cu. in.)

U.S. measure of engine displacement: 1 cubic inch = 16.387 cc.

CUSTOM CAR

An automobile that has been restyled, or an all-new body fitted on an existing chassis.

CYCLE-CAR

A term used to describe the very light production autos made prior to 1922. Usually made

from motorcycle parts and generally powered by single- or twin-cylinder engines.

Disappeared when genuine light cars appeared.

CYLINDER

The hollow tubular cavity in the cylinder block in which the piston travels and in which

combustion takes place.

CYLINDER HEAD

The detachable part of the top of the cylinder block that contains the spark plugs and valves.

It seals the cylinder and forms the top of the combustion chamber.

D

DE DION AXLE

The nineteenth-century axle principle of Count de Dion. The wheels tied by a transverse

tube curved to clear the final drive unit rigidly mounted to the car’s chassis frame. Drive to

the wheels is by universally jointed half shafts. The tube moves vertically on a slide to allow

the wheels to rise and fall independently. General use was dropped in 1914, but still is used

on many sports and racing cars.

DIESEL ENGINE

An internal-combustion engine in which the fuel is injected into the cylinder near the end of

the compression stroke and is ignited by the heat of the compressed air in the cylinder. No

spark plug or carburetor is needed.

DIFFERENTIAL GEARS

The gears that convey engine power to the driving axles and are arranged so as to permit

the rear wheels to turn at different speeds as required when the vehicle is negotiating a

turn.

DISC BRAKE

A type of brake in which two friction pads grip a steel disc that is attached to the wheel, with

one pad on each side. Used on race cars, sports cars, and better passenger cars.

DISTRIBUTOR

The moving part of the internal-combustion engine ignition system that directs the highvoltage

current from the coil to the spark plugs in the proper firing order.

DOS-A-DOS

A four-seater auto in which four passengers face each other or sit back-to-back. Seldom

seen after the early 1900s.

DREAM CAR

A one-of-a-kind futuristic, experimental automobile usually appearing at auto shows to

stimulate interest in the manufacturer’s products. Much design benefit spurs from dream

cars and many reach the production stage.

DRIVE TRAIN

A combination of gears, clutches, shafts, etc., that transmits the engine power to the wheels.

DROPHEAD COUPE

See Convertible. Also called cabriolet on the Continent.

DRY SUMP

Type of internal-combustion engine in which the lubricating oil is stored either in a separate

tank or cooling radiator instead of in the crankcase pan. The oil is pumped to and taken from

the engine by separate pumps.

E

ELECTRICAL SYSTEM

In electric ignition internal-combustion engines, those components required to convert the

electricity produced by the generator into a high-voltage spark for the plugs. Includes:

generator or alternator, points, condenser, coil, distributor and spark plugs plus wiring.

ENGINE TYPES

F-Head Side exhaust valve and overhead inlet valve.

L-Head Both valves on one side of the cylinder.

T-Head Exhaust valve on one side and inlet valve on the other side of the cylinder. (Twincamshafts).

I-Head Both valves located directly over the piston. Also called valve–in-head or overhead

valve engine.

SOHC Single overhead camshaft.

DOHC Double overhead camshafts.

HEMI and HEMI-HEAD (See listings in Glossary.)

EPICYCLIC GEARBOX

A form of gear used by Benz in which small pinions revolve around a central or sun gear

and mesh with an outer ring gear called the annulus. Type used in the Ford Model T. Also

called planetary gears, sun-and-planet gears.

EXHAUST

The system of exhausting the burned gases from an internal-combustion engine consisting

of piping or tubing, silencers, and, at times, resonators.

F

FASTBACK

A car that has an unbroken curved line from the top of the roof to the rear bumper as

opposed to a drop in the line for a near-vertical rear window. In a fastback design the rear

window slope follows the unbroken roofline and is often at less than a 45-degree angle.

FIBERGLASS

A very tough and durable plastic material with fibers running through the plastic. Used for

race car bodies, many sports car bodies, and also enjoys considerable acceptance for

passenger car bodies.

FLYWHEEL

A large, heavy iron or steel disc attached to the rear of an engine crankshaft in order to

provide sufficient centrifugal force to smooth the power impulses from the cylinders.

FOUR-STROKE CYCLE

An internal-combustion engine that requires two revolutions per cylinder or four piston

strokes to achieve a power stroke: internal stroke, compression stroke, power stroke,

exhaust stroke. More efficient than the two-stroke-cycle engine. Also called Otto cycle.

FRAME

A bridge-like, structural base of a car that supports and positions the body and major

mechanical items.

FUEL INJECTION

On internal-combustion engines, a system that injects a precisely measured amount of fuel

into the cylinder at exactly the right moment. Dispenses with the carburetor and increases

engine efficiency.

G

GAS TURBINE

An internal-combustion rotating engine with one main moving part: the rotor with pinwheellike

blades attached. Air is compressed by the first rows of blades and delivered to the

combustion chambers, from which the exhaust is directed to pass the remaining blades and

to generate the power. Power is extremely smooth due to the absence of explosions and

reciprocating parts.

GEARS

Wheels with meshing teeth to transmit power between rotating shafts. When the gear

wheels are of different sizes, a change in speed ratio occurs. Gears are made of hard steel.

G.T. / GRAND TOURING

From the Italian Gran Turismo. A car combining sedan and sports car features in which

engineering is the dominant feature. Combines excellent road handling qualities with relative

comfort. Made in two- and four-seaters with the rear seats always cramped.

H

HALF SHAFT

A rotating shaft that transmits power from the final drive unit (differential) to a power wheel.

Used in independent rear suspension and front-wheel drive. Two are required; one for each

side.

HAND CRANK

A crank handle for manually starting internal combustion engines. Used till about 1930.

Now obsolete.

HELICAL GEAR

A gear in which the teeth are cut at an angle to the shaft. The advantage is that there are

usually two teeth meshing at all times, making for smoother and quieter operation.

HEMI

Slang term for an engine with hemispherical combustion chambers, which allow for larger

and less shrouded valves. Used in many sports and racing cars.

HEMI-HEAD

A hemispherically shaped combustion chamber at the top of the engine cylinder. The

hemispheric shape provides improved efficiency because the forces of the explosion are

directed to the piston by the curved surface of the combustion chamber.

HOOD

The removable or lift-up part of an auto body that covers the engine and allows access to it.

(Bonnet in U.K.)

HORSEPOWER (hp.)

The unit for measuring the power output of an engine. One horsepower is defined as lifting

33,000 pounds one foot per minute.

HOT ROD

A production auto that has been modified by the owner for outstanding speed and

acceleration through extensive changes to the engine, chassis, and body.

HYDRAULIC

A mechanical operation based on incompressibility of liquids, generally oil and sometimes

water, and their ability to offer resistance when being forced into a small cylinder or through

an orifice, thereby transmitting an increase in applied force. Hydraulic brakes and clutches

use this principle.

HYDRAULIC VALVE LIFTER

Valve lifter using hydraulic oil pressure to operate and capable of maintaining zero

clearance between metal parts. Thus, valve noise and wear are considerably reduced, as

are the periodic valve adjustments.

HYPOID GEARS

A type of differential final drive using a spiral bevel gear on the drive shaft, allowing it to be

located below the center of the ring gear on the axle. This makes possible a lower floor in

the car.

I

INDEPENDENT SUSPENSION

Suspension in which each wheel is sprung individually so that any disturbance on the wheel

has no effect on the opposite wheel.

INLINE ENGINE

An engine having the cylinders in a straight line, one after the other. Also called a “straight”

engine.

INTERNAL-COMBUSTION ENGINE

Any engine, either reciprocating or rotary, in which the fuel is consumed in the interior of the

engine rather than outside of the engine.

J

K

KAMM BACK

Named for the German aerodynamicist W. Kamm who discovered that drag begins to

increase after the rear of a car’s cross-sectional area is reduced to 50 percent of the car’s

maximum cross section.

KNOCK-OFF

A single wing nut for fastening a wheel to the hub. Easily removed and replaced, it is struck

(knocked off) with a mallet on the wings.

L

LACQUER

A fast-drying pyroxylin paint often used to finish automobile bodies.

LAMINATED WINDSHIELD

A windshield consisting of a thin layer of rubbery plastic sandwiched between two sheets of

glass. When struck by the head in an accident, it bows out without puncturing, and the

plastic holds the glass to prevent it from splintering.

LEAF SPRINGS

A number of slightly curved, flexible steel plates of varying lengths, mounted one atop the

other. The ends are attached to the chassis, and the middle is fixed to the axle. Also called

semi-elliptic springs.

LIMITED SLIP DIFFERENTIAL

A differential that uses cone or disc clutches to lock the two separate axle shafts. This

forces both driving wheels to transmit the same drive torque regardless of the traction

available. It still allows differential action under normal driving conditions but improves

traction in mud and snow.

LIMOUSINE

A closed, chauffeur-driven automobile in which the driver is separated from the passengers

by a glass partition.

LIVE AXLE

An axle that transmits power either by separate half shafts or by side chains, as opposed to

a dead axle.

LOUVER

A slatted air intake or air outlet. Slats used to capture and control the airflow.

LUXURY CAR

A well-appointed, well-equipped, well-designed and constructed auto varying in size from a

compact to a large sedan.

M

MANUAL TRANSMISSION

A mechanism in the drive train with gears to vary the power and torque delivered to the

driven wheels. It consists of a lever that the driver operates in conjunction with the clutch to

change from one gear to another.

MOCK-UP

A full-size dummy of a car made of wood and clay, used for design studies.

N

NORMALLY ASPIRATED

An engine that intakes air or “breathes” without the assistance of a supercharger or

turbocharger.

O

OIL PUMP

An engine-driven pump that delivers oil, under pressure, to the engine’s moving parts.

OIL RING

The lowermost piston ring that scrapes off excess oil from the cylinder walls and returns it to

the oil pan via vents in the ring and piston.

OTTO CYCLE

See Four-Stroke Cycle.

OVERDRIVE

A small auxiliary gearbox that provides an additional gear ratio. It causes the drive shaft to

turn faster than the engine crankshaft or “overdrive” it. It is engaged manually when under

way and reduces fuel consumption.

OVERHEAD VALVE

See Engine Types, I-Head.

P

PHAETON

The conventional body has 4 doors with convertible top and side curtains rather than roll-up

windows. The four- seater was called a double phaeton, and the six- or seven- seater a

triple phaeton.

PINION

A small diameter gear with a small number of teeth designed to mesh with a much larger

gear wheel or a toothed rod (rack). Used in rack-and-pinion steering and for speed reduction

with an increase in power.

PISTON

A partly hollow, cylindrical metal engine part that is closed at one end and fits into the

engine cylinder. Connected to the crankshaft via the connecting rod and usually fitted with

rings to seal it in the cylinder.

PNEUMATIC TIRE

A circular tube of rubber or synthetic rubber and fabric, and sometimes also steel, attached

to the rim of the car’s wheel, having resilience due to its containing air under pressure.

PRE-SELECTOR GEARBOX

An arrangement that enables the driver to select a gear speed before he needs it and then

depress the clutch pedal when he desires to use the selected gear.

PROTOTYPE

The test model of a new car design that is intended to be produced in quantity.

PUSHROD

A metal rod connecting the valve lifter or camshaft with the valve rocker arm on overheadvalve

engines.

Q

QUADRICYCLE

An early type of light, four-wheeled automobile using bicycle wheels and a frame of steel

tubes.

R

RACK-AND-PINION STEERING

A steering system having a pinion gear at the lower end of the steering column that engages

a rack or a toothed rod that connects to the wheel steering arms.

RADIAL PLY

A tire in which the fabric cords run radially in a line from the wheel hub or straight out from

the bead or around the tubular shape of the tire. Annular belts of fabric or steel mesh add

rigidity. Advantages of this design are: more flexible side walls with a relatively stiff tread

area and a larger and more consistent footprint on the road under all driving conditions.

RECIPROCATING

Motion of an object between two limiting positions. Applied to piston engines because of the

limited up and down motion of the pistons.

RING GEAR

One of the gears in the rear axle that transmits power to the differential from the drive shaft.

ROADSTER

A description of a two-seater open car of sporty appearance with side curtains, instead of

roll-up windows.

ROCKER ARM

A pivoted lever that transmits the action of the pushrod to the valve stem. (Pushrod upward

action is converted to downward push on the valve stem.)

RUNABOUT

An open sporting-type vehicle, lightweight, with two seats and with simple bodywork.

RUNNING BOARD

A long flat board under the car doors that acts as a footstep for the passengers.

S

S.A.E. Society of Automotive Engineers.

A group known for publishing research papers and defining various standards of

measurement.

SEALED BEAM

A one-piece, hermetically sealed headlight in which the filament is an integral part of the

unit, and the lens itself is the bulb.

SEDAN

A closed car for four or more passengers with either two or four doors. (Called saloon in

U.K.)

SELECTIVE TRANSMISSION

The conventional manual transmission of today in which any gear may be selected at will as

opposed to the very early progressive transmission in which the gears had to be selected in

order.

SHOCK ABSORBERS

A term used for what are really dampers. Fittings used to absorb the energy that the wheels

convey to the springs. The dampers keep the springs from continuously rebounding. The

majority of shock absorbers are hydraulic.

SLEEVE VALVE

Consists of metal sleeves located between the piston and cylinder wall. When moved up

and down, holes in the sleeves coincide with inlet and exhaust parts to provide passage for

the gases at the right time.

SPARK PLUG

A device inserted into the combustion chamber of a cylinder on an internal-combustion

engine that provides the electrical gap across which the high-tension voltage jumps. This

creates a spark that ignites the compressed fuel-air mixture.

SPORTS CAR

An agile vehicle that is easily maneuverable, accelerates briskly, brakes positively, handles

well and steers precisely. It is tightly sprung and does not wallow and heave as does a

conventional passenger car and is therefore not as comfortable.

SPYDER or SPIDER

In the early 1900s, a light two-seater car. In the 1950s the word was revived by some Italian

manufacturers for an open two-seater sports car.

STROKE

The back-and-forth motion of the piston. The length of the motion of the piston from top

dead center to bottom dead center.

SUPERCHARGER

An air compressor fitted to an internal combustion engine to force the fuel-air mixture into

the cylinders at a pressure greater than that of the atmosphere. Boosts the power of the

engine.

SUSPENSION

The assembly of springs, shock absorbers, torsion bars, joints, arms, etc., that cushions the

shock of bumps on the road and serves to keep the wheels in constant contact with the

road, thereby improving control and traction.

SWING AXLE

Type of independent rear suspension using half shafts that have universal joints only at their

inboard ends on both sides of the differential. This causes a camber angle change of the

wheel with up-and-down wheel movements.

T

TACHOMETER

An instrument that indicates the number of revolutions per minute at which the engine is

turning.

TORPEDO

An open sports vehicle generally with an unbroken design line from the hood to the back of

the car.

TORSION BAR

A rod in the suspension system that, when twisted from a grip at one end, functions like a

spring.

TOURING CAR (British-TOURER)

An open car with seats for four or more passengers. Early models had no side weather

protection but later were fitted with detachable side screens and curtains. Made until about

1930.

TRANSMISSION

The gear-changing or gear-shifting system through which engine power is transferred to the

wheels. The purpose of gear changing is to keep maximum engine power applied to the

wheels at all times for all conditions, from start-up to high speeds.

TREAD

Width of a car measured from the center line of the wheels. Sometimes called the track.

Also the pattern on the surface of a tire.

TRICYCLE

A three-wheeled, early-type open automobile using bicycle wheels and a steel-tube frame.

TURBOCHARGER

A supercharging device driven by exhaust gases from the engine.

TWO-STROKE CYCLE

An internal-combustion engine that requires only one revolution per cylinder or two piston

strokes (up and down) to achieve a power stroke. Rarely used in automobiles.

U

V

VALVE

Device that opens and closes the combustion chamber of an internal-combustion engine to

admit the fuel-air mixture or exhaust the gases.

VALVE-IN-HEAD

See Engine Types, I-Head.

VEE ENGINE

An engine with cylinders arranged in two rows at an angle to the common crankshaft. Has a

“V” shape when viewed from the front.

VIS-A-VIS

A four-seater in which two passengers faced the driver. Used around the turn of the century.

VOITURE LEGERE

A light car, especially a racing car falling between the heavy cars and the voiturette. Term

seldom used to describe production cars. Not used after 1914.

VOITURETTE

Early two-seater touring car. Name first used by Leon Bollee and then applied to any small

car.

W

WHEELBASE

The distance between the centers of the front and rear wheel axles as viewed from the side

of the car.