auto dictionary

8/9/2019 Auto Dictionary

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A

Acceleration Acceleration is what occurs when the car moves forward from a stop or from a

slower speed to a higher speed.

Accelerator Pedal A foot operated device which, directly or indirectly, controls the flow of fuel and

air to the engine, controlling engine rpm. Also called the gas pedal. See Throttle.

Accelerator pump Accelerator pumps are found in cars equipped with carburetors. When you

accelerate, the accelerator pump delivers extra fuel through the accelerator pum

circuit to allow the engine to deliver more power.

Accessory Refers to a power-operated feature on a car. For instance, power windows and p

locks would be considered accessories.

Accumulator A container in the air conditioning system used to remove moisture or water. Th

helps to extend a/c compressor and other component life.

Actuator An electrical mechanism for moving or controlling something indirectly instead

hand, such as a door lock. Output device the PCM controls such as solenoids, relfuel injectors and stepper motors.

Air Conditioning An Original Equipment or Aftermarket accessory system that cools and dries th

incoming passenger compartment air. Aka: a/c

Air filter This device filters the air that goes into your engine. Without an air filter, harmf

particles would enter your car's engine and cause internal wear and damage.

Air pump Many emissions systems include an air pump, which pumps fresh air into a vehic

exhaust to help complete the combustion process and reduce emissions.

Airbag A safety device, consisting of impact sensors, computer, a detonation device and bag, that protects the driver (and in some cases, the passenger) in a crash by infl

a cushion hidden in the steering wheel and dashboard.

Alignment Alignment is when all your wheels are pointing in exactly the right direction. If o

wheel is off by even one or two degrees, it is considered out of alignment. When a

vehicle is out of alignment, excessive tire, steering system and suspension system

wear may be the end result.

All-wheel drive

(AWD)

An all-wheel drive system has differentials which split the engine's power to the

wheels according to which have the most traction.

Alternator An alternator is an engine-belt driven device that converts mechanical energy inelectrical energy. The electrical output keeps your battery charged and operates

vehicle's electrical system.

Anti-lock braking

system (ABS)

ABS uses a series of sensors, a computer and a high-pressure hydraulic pump to

prevent your brakes from locking up during sudden stops on slippery surfaces.

Anti-roll bar The anti-roll bar is a suspension system component that helps a vehicle to stay fl

and not lean excessively when cornering. Also called a sway bar or stabilizer bar

Anti-theft code (radio) Many modern radios have special anti-theft circuitry that prevents them from

operating after being disconnected from a power source. For these types of radio


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is necessary to enter a factory-supplied code to get the radio to work again.

Antifreeze The fluid mixed with water that is put into your vehicle's radiator. Antifreeze is

traditionally green in color; however, newer long-life antifreezes may be red or

orange. Please refer to your vehicle's owner's manual for the proper antifreeze fo

your vehicle.

Automatic choke Automatic chokes use either a heat- or computer-controlled element to turn on a

off automatically as needed.

Automatic temperature

control

A computerized system that automatically maintains a selected temperature for

car's interior. Also called climate control.

Automatic

transmission

Automatic transmissions have hydraulically operated gear sets, which require no

gear shifting or clutching by the driver.

Axial Referring to a type of air conditioning compressor that compresses the R-12

refrigerant in a horizontal cylinder and piston compressor. Compare to Radial.

(Remember, Axial is LONG like an axle; Radial is SHORT like a radial tire.)

Axle The shaft around which the wheels rotate.

B

Balance Tube A tube or pipe connecting the exhaust head pipes in a dual exhaust system. This

balance tube acts like a pressure equalizer enabling both exhaust pipes to flow at

same pressure.

Balancing (tire) The process of making sure a tire will not cause vibration when driving. By usin

computerized machine, a technician can locate a non-balanced tire and balance i

attaching weights on the wheel rim to even out the tire's balance.

Ball joint A joint between two parts that allows movement in any direction by the two part

Ball joints are most often found in a vehicle's suspension and steering systems.

Barrel (carburetor) A barrel is a venturi in a carburetor where air and fuel are mixed, then taken in

the intake manifold and then to a cylinder. Carburetors usually have from one to

four barrels, depending on the engine application.

Battery An electrical storage container designed to produce DC voltage by means of an

electrochemical reaction. This reaction occurs in the container between the lead

plates and sulfuric acid. Voltage is supplied to the starting, ignition and other

electrical systems.

Bearings Bearings are used to prevent wear when two moving parts are placed very close

each other.

Bleeding Bleeding removes fluid from a system, such as a brake or clutch system. When a

technician bleeds a brake system, the old fluid is completely removed and replac

with new fluid.

Blower Motor An electric motor with a fan designed to supply a current of air at a moderate

pressure. A blower usually consists of a fan assembly, a motor, and a suitable cas


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The blower case is usually designed as part of the heating/air conditioning system

Blueprinting The procedure of dismantling an engine, measuring, machining components, and

reassembling it to the minimum factory tolerances. This procedure usually will

provide more power and efficiency

Body The assemblage of components, including windows, doors, seats, etc., that provid

enclosures for passengers and/or cargo in a motor vehicle.

Body Control Module

(BCM)

A device powered by the main vehicle computer that takes input from various

sensors to control components such as the air bag, headlight sentinel and door ch

Brake A device, such as the disc or drum brake, for retarding motion. This is usually

created by means of friction caused by a clamping force from a stationary calipe

shoe, against a rotating rotor or drum.

Brake booster A device that uses engine vacuum or hydraulic pressure to multiply or boost the

pedal effort of the driver while braking, thus adding more hydraulic pressure to

brakes for added stopping power.

Brake caliper A c-shaped device used with disc brakes. When a driver presses on the brake pedthe caliper piston squeezes the brake pads against the rotor and causes the car to

slow down or stop.

Brake drums Brake drums are drum-shaped components which contain internal brake shoes,

which expand and press against the drum, when the driver presses on the brake

pedal, slowing or stopping the car.

Brake fluid A special type of hydraulic fluid designed specifically for brakes. Brake fluid

transfers the motion of a driver stepping on a brake pedal directly to operate a b

caliper or wheel cylinder.

Brake lines Metal tubing and rubber hoses which connects each brake caliper or wheel cylinto the brake master cylinder.

Brake master cylinder As the main component of a braking system, the brake master cylinder takes the

pressure applied to the brake pedal by the driver and distributes it evenly to all f

brakes on a car.

Brake pads Brake pads are used specifically with disc brake systems. The pads fit inside the

calipers, and create friction and stopping power when pressed against the brake

rotor. When you have your disc brakes replaced, it is often just the pads that are

being replaced.

Brake pedal The pedal to the left of the accelerator pedal that controls a car's brakes. When ystep on the brake pedal, the car slows down or stops.

Brake rotors (discs) Brake rotors, or discs, are fitted to most modern cars. They are flat, circular pla

that rotate with the wheel when you drive. When you step on the brake, the brak

calipers squeeze the brake discs, slowing or stopping the car.

Brake shoes Brake shoes are used specifically with drum brake systems. Brake shoes fit insid

brake drum, and are pressed against the drum by a wheel cylinder when the bra

are applied, thus slowing or stopping the car.

Braking system The braking system in a modern car consists of the brake pedal, a power brake


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production vehicles, carburetors have been replaced by electronic fuel injection.

Carburetor jet A fitting inside a carburetor that meters fuel into a metering circuit where it is m

with air in the venturi.

Caster An alignment spec where an imaginary line through the ball joints (steering axis

intersects a vertical line through the front wheel center. Positive caster delivers

directional stability and improved steering feel.

Catalyst A substance that can increase or decrease the rate of a chemical reaction betwee

substances without being physically consumed in the process. A catalyst, which

reduces engine emissions, is used in a catalytic converter.

Catalytic converter An in-line, exhaust system device, containing a catalyst, which reduces engine

exhaust emissions. Converters are located near the exhaust manifolds or headers

maximum efficiency.

Charging system The system which maintains the electrical charge in your vehicle's battery. The

charging system consists of the alternator, voltage regulator and battery.

Chassis The suspension, steering, and braking components of a vehicle. Everything but tbody, fenders, etc.

Choke A device in a carburetor which shuts off airflow so that the engine runs rich. Thi

necessary to start a cold engine.

Circuit A complete electrical path, usually includes the electrical energy source. May als

used with fluids or air. The headlights and brake system are examples of an elect

and hydraulic circuit.

Cleaner (Air) A housing holding a filter fitted in the intake system of parts requiring clean air.

engine air cleaner filter removes particulates before they can enter the intake sys

and cause damage.

Clear-coat finish Many modern cars have a clear-coat finish. This is an extra, clear layer of paint

goes on top of the last color coat of paint to protect it from scratches, chips and

other environmental damage.

Climate Control Describes temperature/ventilation environment in the passenger compartment.

Climate adjustments are made by adjusting the heater/ ventilation and A/C cont

Aka automatic temperature control.

Closed Loop (Engine) An operating mode of the PCM enabling modification of pre-programmed

instructions based on a feedback system. By constant exhaust sampling, a closed

system allows pre-programmed engine adjustments to occur while running in orto minimize exhaust emissions.

Clutch A mechanical device which uses mechanical, magnetic, or friction type connectio

facilitate engaging or disengaging two rotating members. Examples: the friction

clutch located between the engine and manual transmission or the a/c clutch.

Clutch - cable-

operated

A cable-operated clutch uses a metal cable between the clutch pedal and clutch f

to control clutch engagement.

Clutch - hydraulic A hydraulic clutch uses a hydraulic circuit between the clutch pedal and clutch f

to control clutch engagement.


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Clutch disc The friction material lined plate that delivers power from the engine to the

transmission.

Clutch pedal The pedal on manual transmission cars that operates the clutch.

Clutch throw-out

bearing

A bearing that lets the clutch pressure plate and disc smoothly engage and diseng

with minimum wear.

Clutch-operated fan An engine cooling fan that uses a heat-activated, viscous-fluid clutch which turnsfan on and off as needed.

Code A system of symbols (as letters, numbers, or words) used to represent the meanin

information. An engine trouble code shows where a vehicle system or component

failure may be occurring.

Coil (Ignition) A device consisting of fine wire windings around an iron core, which is designed

step up battery voltage. The high voltage created (35,000 volts or more) is deliver

to the spark plug so ignition can occur.

Coil Spring A spiral-wound steel wire coil, of various wire diameter thicknesses and coil stac

heights, used to suspend a vehicle. Can be used in cars and trucks, both front andrear, depending on the application.

Combustion The process by which the air/fuel mixture burns within an engine to create powe

Combustion chamber The area in the cylinder head where air/fuel is ignited to create power.

Comprehensive

insurance coverage

Comprehensive coverage includes protection against theft and accident damage,

regardless of fault.

Compression gauge A special gauge used by technicians to measure how much pressure a cylinder ca

create.

Compression test A test to see how much pressure a cylinder can create.

Computer (PCM) Many modern cars have a central computer called an engine control unit (ECU)

power train control module (PCM). This controls the car's fuel and ignition syste

by taking information from various sensors to determine how to run the engine w

the most efficiency and power.

Constant Velocity

Joint

A coupling that allows a shaft to turn continuously at various angles when coupl

with another shaft. Usually associated with front-wheel or all-wheel drive vehicle

Converter (Torque) A fluid coupling device which multiplies torque between an engine and automati

transmission/transaxle. When a vehicle is stopped, a converter allows enough fluslippage, so the engine can idle without stalling.

Coolant A fluid used in the radiator for heat transfer. Mixed with water, coolants usually

contain rust inhibiting additives and provide antifreeze protection. Some new ve

coolants are designed to last 100,000 miles. Please refer to your owner's manual f

the proper antifreeze for your vehicle.

Coolant reservoir Many cars have a clear plastic reservoir that allows the owner to see the level of

vehicle's coolant. Check your owner's manual to find the coolant reservoir on yo

vehicle.


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Cooler A heat exchanger that reduces the temperature of the cooling medium. Two

examples would be a engine radiator or oil cooler.

Cooling system The system of components that keeps your engine at the correct operating

temperature. The cooling system includes the radiator, radiator cap, coolant

reservoir, cooling fan, water pump, thermostat, hoses, heater core, heater valve,

antifreeze.

Core (Price/Charge) A payment that is credited back to the buyer after they have returned a rebuildaCore unit to the retailer. A rebuilt alternator purchase would have a core charge

would require returning the old one to receive the credit.

Cracked paint Cracked paint occurs when a paint is so damaged, the surface actually develops

cracks. These cracks may spread in a spider web fashion across the surface of th

paint. Cracked paint is unrestorable, and must often be completely removed whe

car is repainted.

Crankshaft The engine component which converts piston reciprocating (up and down) motio

into rotary motion at the flywheel or flexplate. Connected to the clutch or torque

converter, engine torque is delivered to the drivetrain to move the vehicle.

Crazed paint Crazed paint occurs when paint is so damaged, the surface actually develops hai

cracks. These cracks may spread in a spider web fashion across the surface of th

paint. Crazed paint is unrestorable, and sometimes has to be completely removed

when a car is repainted.

Cruising Cruising is a driving style whereby the driver maintains a set speed with very lit

fluctuation.

CV joints CV (constant velocity) joints are part of a car's driveline. They allow a wheel to

rotate freely in any direction while still receiving power from the axle.

Cylinder Cylinders are the large round holes in the engine block in which combustion occThis combustion forces the piston down and turns the crankshaft.

Cylinder Head A removable part located on the top of the cylinder block; it usually contains

valvetrain components and combustion chambers. For an overhead cam engine,

contains the camshafts as well. A head is an important influence in determining

engines overall power and efficiency.

D

Data General term for information, usually represented by numbers, letters and symb

A gas gauge is an instrument that provides data to the driver.

Defroster A setting of your car's heating controls that lets you easily remove frost and fog f

your vehicle's windows.

Diagnostics The process of identifying the cause or nature of a condition or situation. Most c

have computer diagnostic systems that help the technician to determine correctiv

repairs.

Diesel engine A type of engine that uses heat caused by engine compression rather than spark


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efficient combustion and lower emissions. GM used an electric grid system.

Electric cooling fans Electric cooling fans are part of many cars' cooling systems. They use a heat

activated switch to turn on and off as needed to help keep your engine cool.

Electric motor Any device that converts Electromagnetic force to motion, or vice-versa. Electric

motors are often used in accessories such as power windows or power seats to

provide movement with minimal effort by the user.

Emergency brake Also called the parking brake. A braking system which is independent of the ma

hydraulic system. It can be used to slow or stop the vehicle if the primary brakes

or to hold the vehicle stationary though the brake pedal is not depressed. It usua

consists of a foot pedal or hand lever that actuates either front or rear brakes

mechanically through a series of cables and linkages.

Emissions Emissions are the byproducts of combustion. After combustion is complete, wate

gases, and carbon are released through the car's exhaust system as emissions.

Emissions equipment Emissions equipment is equipment required by the government to keep a car's

exhaust emissions to a minimum. Emissions equipment includes catalytic conver

air pump, and oxygen sensor.

Engine A machine designed to convert thermal energy into mechanical energy to produc

force or motion. Connected to a drivetrain, an engine's mechanical energy, or tor

moves a vehicle. An engine can run by using gas, diesel fuel, steam or other fuel

sources.

Engine accessory An engine accessory is a peripheral piece of equipment that runs directly off of t

engine's power to supply energy or a fluid to another part of the car. Engine

accessories include the alternator, power steering pump, air pump, air condition

compressor, as well as many others.

Engine block The engine block is where the cylinders and pistons reside. The block is the stronpart of the engine and withstands tremendous pressures while the engine is

operating.

Engine mounts Engine mounts are often made of metal and rubber. Engine mounts help suppor

engine, and also help to prevent engine vibrations from shaking the entire car.

Engine temperature

sender

The engine temperature switch and sending unit measure the temperature of the

engine's coolant. They send this information to the engine temperature warning

and engine temperature gauge, respectively. Compare to coolant temperature se

(CTS) which transmits the coolant temperature to the computer, and the radiato

fan switch which engages the radiator's cooling fan.

Evaporative Emissions

Control

A system which filters evaporating fuel fumes from the vehicle's fuel system and

routes them to the engines intake to be burned.

Exhaust Gaseous by-products of combustion emitted from an engine. Exhaust flows from

engine, through the muffler and exits from the exhaust system.

Exhaust Gas

Recirculation

An engine system where a small portion of exhaust gases are recycled into the

combustion chamber. This lowers combustion temperatures and reduces oxides

nitrogen emissions. The EGR system is important for a smooth performing engin


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Exhaust hanger Exhaust hangers keep the exhaust system in place, while also preventing excess

vibration and noise from reaching the passengers.

Exhaust manifold The exhaust manifold carries the exhaust from the cylinder head to the exhaust

system.

Exhaust system The exhaust system carries exhaust away from the engine and away from the car

The exhaust system includes the exhaust manifold, the catalytic converter, the

muffler, and the tailpipe.

F

Fan Designed to supply air flow as the fan blades rotate, a fan can be driven by eithe

motor or belt.

Fan belt Also called a drive belt or serpentine belt. Fan belts are used to drive the engine'

accessories, such as the alternator, power steering pump, or air conditioning

compressor. A serpentine belt is a wide single drive belt that drives multiple engi

accessories.

Fan clutch A viscous-fluid clutch that controls how fast an engine fan rotates to help cool an

engine.

Fan motor An electric motor which drives a fan to direct air, through a radiator or car's

interior, for example.

Feedback Carburetor A computer-controlled carburetor that adjusts the air/fuel mixture according to

input from various sensors, via a mixture-control solenoid. The solenoid's

adjustment helps maintain the correct air/fuel ratio and minimizes exhaust

emissions.

Feeler Gauge An instrument used to measure the distance between two metal contacts. A feele

gauge could be use to measure spark plug gap, point gap or valve clearance.

Fiberglass matting and

resin

These materials are often used to fill in large rust holes where filler would be una

to work, and where welding in new metal would be difficult.

Final Drive Ratio The ratio between the pinion and ring gear in the drive differential. A numerical

high ratio enhances vehicle acceleration and pulling ability, while a numerically

ratio enhances highway cruising and fuel economy.

Flexplate Secured to the end of the crankshaft, it has three functions; the ring gear for the

starter on the outside diameter; helps to balance out engine vibrations; a connec

between the transmission torque converter and the engine allowing flexing. Com

to flywheel for manual transmission.

Flushing Flushing is a means of entirely replacing the fluid in a given system. For instance

when a technician flushes a cooling system, all the old coolant is removed and

completely replaced with new.

Flywheel Secured to the end of the crankshaft, it has three functions; the ring gear for the

starter on the outside diameter; helps to balance out engine vibrations; a connec

between the transmission clutch and the engine. Compare to flexplate for autom


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transmission.

Four-wheel drive

(4WD)

A drive system in which both the front and rear wheels are connected through th

driveshaft and axles to the transmission, usually via a transfer case. A 4WD syste

can be full time or part time. Sometimes called 4x4 (four by four).

Front-wheel drive

(FWD)

A front-wheel drive vehicle sends its power from the engine to the front wheels o

car.

Fuel Any combustible substance burned to provide heat or power. While gasoline is t

most common, other fuels include diesel, ethanol and natural gas.

Fuel filter A car's fuel filter removes debris and contaminants from fuel before it reaches th

carburetor or fuel injection system.

Fuel injection Fuel injection is a system by which fuel is directly sprayed into the intake manifo

or intake port at high pressure. Fuel injection is often controlled by a computer,

allowing precise monitoring of efficiency and performance by the car's computer

Fuel injector A device for delivering metered, pressurized fuel to the intake system or individu

cylinders. An injector sprays fuel, which helps atomization for a more dense mixwhen combined with incoming air.

Fuel pump The fuel pump moves gas from the gas tank and delivers it to the fuel injection

system or carburetor.

Fuel starvation Fuel starvation occurs when fuel, for one reason or another, is prevented from

reaching the carburetor or fuel injectors.

Fuel system The fuel system is the system by which fuel is stored and delivered to each cylind

The fuel system includes the fuel tank, fuel tank level sending unit, the fuel pump

fuel filter, and fuel lines. For carbureted cars, the fuel system also includes the

carburetor. For fuel injected cars, the fuel system also includes injectors, fuelpressure regulator and often a main computer.

Fuel tank level sending

unit

This unit measures the amount of gas in the fuel tank and sends that information

the vehicle's gas gauge and, if equipped, a low gas level warning light.

Fuses A device designed to open and protect equipment or a circuit from being destroy

when the circuit is subjected to a power overload. This is a non-reversible action

there are 3 main types of fuses; glass, ceramic and spade.

G

G-Force Unit of measurement used to describe lateral acceleration generated while the ve

is driven in a steady state turn on a skid pad circle. An average sedan generates 0

G of lateral acceleration. Measured in "gravities", one G equals the earth's grav

sea level.

Gas - grade This is a general term that refers to a gasoline's general quality - for instance, its

octane rating and package of additives. The two common terms for gas grades ar

"regular" for low-grade gas, and "premium" for high-grade gas.


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Gasket A material usually made of rubber, cork, metal, paper or a combination thereof

is placed between two surfaces to ensure proper sealing against the passage of air

liquid or vapors. Valve cover gaskets are one example of a popular gasket.

Gauge A gauge is a type of instrument that measures or displays levels of a certain syste

For instance, the gas gauge in a vehicle measures the fuel level, while the

temperature gauge measures the engine temperature.

Gear selector The gear selector is the lever that lets you select a certain gear with an automatictransmission. In modern cars, the gear selector is often connected to the brake pe

so that you can only shift into drive or reverse when your foot is on the brake.

Gear synchronizers Gear synchronizers allow you to upshift and downshift a manual transmission

without grinding gears. They do this by synchronizing, or matching, the speed of

engine and the speed of the gear you are selecting. If your car didn't have gear

synchronizers (also known as synchromesh), you would either have to match the

engine speed to the gear speed (known as double-clutching) or else grind your ge

every time you shifted. See also "synchromesh".

Gearshift lever The gearshift lever is the lever that allows you select the different gears of a

transmission.

Gearshift linkage This is a series of rods and/or cables that connect the gearshift lever or gear selec

to the transmission.

Generator A generator is like an alternator in that it generates electrical current to both ke

the battery charged and supply electricity for a vehicle's electric system. It differ

from an alternator in that a generator generates direct current (DC) where an

alternator generates alternating current (AC).

Glass Pack A muffler design that contains fiberglass packing around a perforated internal p

(straight through) which slightly deadens exhaust noise. Usually louder than a

conventional replacement muffler.

Glazing (belts) Glazing is a shiny coating on the inside surface of a fan, or serpentine belt. Glazi

occurs when the belt slips repeatedly at a high speed. It is a sign that the belt nee

replacement.

Glow Plug A combustion chamber heat generating device to aid starting diesel engines. Wh

the glow plug heats the combustion chamber to the proper temperature, the igni

key can be turned to engage the starter.

Governor An electronic or mechanical device designed to limit engine speed. Large diesel

engines usually are equipped with governors.

Ground An electrical conductor used as a common return for completing an electric

circuit(s). Car batteries contain a ground terminal, usually the negative terminal

H

Halfshaft An exposed axle driveshaft usually having a CV (constant velocity) joint on eithe

end, being driven from a differential. Also called a CV axle.


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Hazard relay The hazard relay controls the flashing of the hazard warning lights.

Head gasket The head gasket seals the cylinder head to the engine block. It is subject to

tremendous pressures, and often fails if and when an engine overheats.

Headers Constructed from steel tubing, headers provide a smooth and efficient exhaust fl

path from the exhaust port to the exhaust system. Headers are frequently used in

performance engine applications and are generally less restrictive than the stock

exhaust manifold, resulting in increased power.

Heater core The heater core is a miniature radiator that sits in the dashboard area. When th

heater is turned on, it opens the heater valve which lets hot coolant into the heate

core, which then warms the air coming into the vehicle's interior.

Heater ducts The heater ducts are the passageways through which warmed air enters the inte

of the vehicle.

Heater fan The heater fan is the interior fan attached to a blower motor that controls the sp

of air being introduced into the interior.

Heater valve The heater valve is controlled by the interior heating controls. When you turn onyour vehicle's heater, the valve opens and allows hot coolant to enter the heater c

which then warms the air forced through the heater core by a blower motor, and

warmed air then enters the vehicle's interior.

Heater/heating system The heating system warms the air brought into a vehicle's interior. The heating

system is connected to the cooling system and consists primarily of the heater cor

heater valve, and, if equipped, a climate-control system.

Hex Wrench Also known as an Allen wrench, it is a hexagonal tool that fits and operates faste

with hexagonal openings.

Hoses (cooling system) The cooling system hoses allow coolant to circulate between the radiator, engineheater. Over time, they deteriorate, and should be checked annually for conditio

and possible damage.

Hub Hub is a generic term for a circular area where a component is mounted. For

instance, there are hubs for every wheel on your car.

HVAC Stands for Heating, Ventilation, Air Conditioning. These systems are controlled

the car's climate control panel.

Hydraulic circuit The hydraulic circuit is a closed system of tubes and components that contain

hydraulic fluid. When pressure is applied at one end of the hydraulic circuit, it

travels through the tubes to the other end.

Hydrocarbon An organic compound containing various carbon and hydrogen molecules linked

together in fuel. Gasoline is a hydrocarbon fuel. If the fuel is not burned efficient

the cylinders, hydrocarbon molecules are released into the atmosphere as polluta

I

Idle Running engine speed with vehicle at rest and accelerator or throttle pedal not


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depressed. While waiting at a stop light, the engine is at idle.

Idle circuit This is a special kind of circuit found in a carburetor that only operates when th

engine is at an idle.

Ignition Complete system used to step up battery voltage to a higher voltage and deliver i

the spark plug to complete the combustion process. When the key is turned on, t

ignition system is energized.

Ignition

Advance/Retard

The advancing or retarding (in crank degrees) of ignition spark relative to the pi

location in the cylinder. Ignition timing should be set to factory specifications.

Ignition condenser The condenser collects and stores excess electrical energy in an older ignition sys

that has points. This prevents that extra energy from jumping across the points w

they first open and close.

Ignition module Part of the ignition system which instructs the ignition coil to send current to the

distributor.

Ignition points Part of the ignition system which allows the ignition coil to send current to the

distributor in older vehicles. Ignition points do this by opening and closing, whicopens and closes the electric circuit. Electronic ignition systems have made igniti

points and condensers obsolete.

Ignition switch This is the switch where you insert the key that starts the vehicle.

Ignition system The ignition system contains the components that supply spark to the vehicle's sp

plugs. These include the battery, the ignition coil, the distributor (including the c

and rotor), the spark plug wires, the ignition module, and the spark plugs

themselves. Older cars also have ignition points and an ignition condenser.

Injector (fuel) A device for delivering metered, pressurized fuel to the intake system or individu

cylinders. A fuel injector sprays fuel, which helps atomization for a more densemixture, when combined with incoming air.

Instrument An instrument measures levels of a certain system and provides a visual key for

levels. For instance, the gas gauge in your car measures the fuel level, while the

temperature gauge indicates the engine temperature.

Intake Air Air used in combustion that flows through an air filter, throttle valve and is

distributed to each cylinder by the intake manifold.

Intake manifold The intake manifold is located between the vehicle's fuel system and the cylinder

head(s) to distribute the fuel/air mixture to individual cylinders.

K

Knock (Engine) The sharp, metallic sound produced when two pressure, or flame fronts collide i

combustion chamber. This could be the result of incorrect ignition timing or the

wrong grade (octane rating) of gas. Higher octane fuel can eliminate knock due t

increased resistance to cylinder pressure.


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L

Lathe Device used to machine the outside and/or inside of a metal object as it rotates. A

brake lathe is used to smooth the exterior pad surface of a brake rotor or the int

of a brake drum.

Leaf Spring A thin, long, arched, steel spring that is attached between a vehicle frame and axact as a suspension. More than one spring leaf are often clamped together to ach

a desired load capacity or spring rate.

Leakdown test A leakdown test is used to find excessive wear in an engine. When a technician

performs a leakdown test on a vehicle, each cylinder is tested to see how well it h

pressure. If a cylinder is unable to hold pressure, your technician can pinpoint w

component of the cylinder (piston rings, valves, etc) has the problem that is caus

the pressure loss.

Liability insurance Liability insurance is coverage only for damage that you inflict on other people o

their possessions. It does not cover theft or damage to your vehicle.

Limited-slip

differential (LSD)

An LSD senses the slippage of each wheel and sends and redirects power to the w

with the most grip. Many high-performance vehicles have LSDs.

Link

(Electrical/Electronic)

General term used to indicate a communication connection between two data po

Mechanics use a link to retrieve trouble codes from a vehicle's ECU in order

facilitate repairs.

Linkage A series of bars, levers, yokes, rods, or cables used in unison to transmit motion

one unit to another. Transmission shift linkage connects the shifter to the

transmission and allows gear selections to be made.

Loaded (caliper) A disc brake caliper, which comes complete with all the installation hardware su

as emergency brake lever, spring, bracket and brake pads. This speeds a caliper

installation during replacement.

Lug nuts Lug nuts attach a car's wheel to its hub. Also known as wheel nuts.

M

MacPherson strut A shock absorbing component in a front suspension system that is mounted dire

above the upper control arm. Many lightweight, uni-body cars use thisuncomplicated type of front suspension.

Main Bearings Soft metal alloy inserts, bonded to a steel back, used to allow the crankshaft to ri

on a cushion of oil formed between the crank journal and bearing surface. Main

bearings often last throughout the life of the engine.

Manifold A component designed to collect and/or distribute an engine's air and/or fuel

mixture, or exhaust.

Manual choke A manual choke system has a cable that lets the driver control the carburetor's

choke operation. Most newer cars with carburetors have automatic chokes instea


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Open Loop An operating condition or mode in the vehicle's intake fuel system controlled by

vehicle's PCM, based on pre-programmed instructions, usually when an engine i

the cold start-up mode.

Output Shaft A shaft that drives the next element in the power train, like the front driveshaft y

slipping over the output shaft of the transmission, which drives the wheels.

Overboost (turbo) Overboost occurs when a turbo's wastegate does not release excess intake pressu

This pressure instead enters the engine, causing potentially significant damage toengine.

Overdrive Overdrive is a transmission gear that allows the engine to turn at a reduced rpm

a given road speed.

Overhead cam (OHC) An overhead cam engine has its camshaft in the cylinder head, above the valves

cylinders. This allows the camshaft to directly open the valves without using

pushrods.

Overhead valve

(OHV)

An overhead valve engine has its camshaft in the engine block. It uses lifters,

pushrods and rocker arms to open and close the valves in the cylinder head.

Overheating Overheating occurs when an engine reaches too high of an operating temperatur

Overheating may lead to potentially significant engine damage.

Overinflation (tires) Overinflation occurs when a tire is inflated beyond the pressure recommended b

manufacturer. Overinflating can lead to increased tire wear and sudden tire failu

Owner's manual The owner's manual is the booklet supplied with all cars when they are sold new

usually placed in the glovebox. The owner's manual contains information about

vehicle's equipment and options, what kinds of fluids and lubricants to use, and

to maintain your car. If you don't have an owner's manual, one can be obtained

the vehicle's manufacturer.

Oxides of Nitrogen Commonly known as NOX, it is various combinations of one part nitrogen and o

or more parts of oxygen, which is a by-product of combustion at a very high

temperature when using gasoline as a fuel. NOX is a component of smog.

Oxygen sensor The oxygen sensor is part of the exhaust and emission systems and is usually loca

in the exhaust manifold. It senses the amount of oxygen in the exhaust gases and

adjusts the fuel system's operation accordingly to minimize emissions while

improving economy and performance.

P

Park (gear) This is a gear found only on automatic transmissions. The park gear locks a vehi

transmission in place, preventing the car from moving.

Park/neutral safety

switch

This is a switch found on many modern automatic transmissions that prevents a

vehicle from starting unless the gear selector is in park or neutral.

Parking brake Also known as the emergency brake. The parking brake is used when parking on

incline to prevent the car from rolling away. The parking brake is usually cable

operated and can be used as a backup if the regular hydraulic brake system fails


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Parking brake cable The parking brake cable connects the parking brake pedal or handle to the park

brakes themselves.

Parking brake

shoes/pads

The parking brake shoes/pads are just like normal brake pads or brake shoes. T

only difference is that they work specifically with the parking brakes, and are

independent from the regular brake system.

Petcock A small valve used for draining liquids. Petcocks are usually associated with

radiators and are located at the bottom of one of the radiator's tanks.

Pinging (engine) A noise made in the engine caused by a pre-ignition condition. When your engin

knocks or pings, it is a sign that the engine is firing at the wrong time. This could

because of improper ignition timing, an incorrect grade of gas, or another ignitio

fuel system fault.

Piston An aluminum-based cylindrical part located inside an engines cylinder (combust

chamber) that moves up and down, transferring the force of combustion to the

connecting rod and then to the crankshaft, which causes rotation.

Piston Ring Usually 3-4 rings that fit on the outer diameter of the piston beneath the piston t

which seals the pressure of combustion in the cylinder (top 2 or 3 rings called thecompression rings) and aids in scraping residual lubricating oil from the cylinde

walls (bottom ring called the oil ring).

Piston-To-Valve

Clearance

The distance or space between the intake and exhaust valves in relation to the to

the piston when the piston is at the top of its stroke, known as TDC, or top dead

center.

Pitman Arm Arm attached to the pitman shaft on a steering box that moves the relay rod as t

steering wheel is turned in a mechanical (not rack and pinion) steering system..

Plastic polish A special type of polish designed to gently remove scratches and yellowing from

plastic items such as convertible top windows and plastic lenses.

Play Play occurs when there is excessive free movement in a vehicle's steering system.

instance, if you turn your steering wheel either direction from the center and not

happens for the first two inches of travel, your steering system has play in it.

Porting The enlarging of the exhaust and intake passages to increase flow through the

cylinder head. When done correctly, this process can add a significant amount of

power and increase fuel efficiency.

Posi Also known as Positraction, which is a limited-slip differential (LSD) distributin

power equally to both drive axles through a series of plates, clutches and springs

Positive Crankcase

Ventilation (PCV)

This system relieves pressure and recirculates fumes created by the motion of th

crankshaft, connecting rods and pistons in the crankcase, by sending them throu

one-way valve back into the engine to be burned in the combustion process.

Power Steering A system which provides additional hydraulic force, generated by a pump, to the

steering mechanism, either a steering box or rack, reducing the driver's turning

effort at the steering wheel.

Power steering fluid A special type of fluid designed for power steering systems.

Power steering pump The power steering pump transfers power steering fluid under pressure to other


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power steering system components, allowing the driver to steer with minimal eff

Power train The elements of a vehicle by which motive power is generated and transmitted to

driven axles. Examples of power train components are the engine, transmission a

differential.

Power train Control

Module (PCM)

A module commonly referred to as the vehicle's "main computer", it controls ho

the engine and transmission operate via input from many sensors. Aka: ECM

(Electronic Control Module), EEC (Electronic Engine Control) and ECU (ElectrControl Unit).

Prechamber A dual-chamber combustion system for diesel engines with a centrally located

auxiliary combustion chamber for reduced emissions and less diesel soot.

Pressure (Absolute) The pressure referenced to a perfect vacuum, usually found in the intake manifo

Commonly known as the MAP, or Manifold Absolute Pressure.

Pressure

(Atmospheric)

The pressure of the air outside of the engine at any given temperature and altitu

Sometimes called barometric pressure, it is usually referenced as the "baro" sen

reading in the power train control system.

Pressure (Differential) The pressure difference between two areas in the engine, such as between the

pressure in the intake manifold and the atmospheric, or outside, air pressure.

Pressure Plate The part of a manual clutch system with a covered spring and clamping ring

mounted over the friction disk, to the flywheel. When the pressure plate is engag

clamps the friction disk to the flywheel, which turns the input shaft of the

transmission. It allows the smooth application of power to the transmission. Also

known as a clutch cover.

Primer A type of paint applied to a vehicle's surface to increase its compatibility with th

topcoat and/or to improve the corrosion resistance of the base metal. The primer

paint is applied first, then the final topcoat, or color coat of the vehicle is appliedtop of the primer coat.

Proportioning Valve A valve in the brake hydraulic system usually located in or near the brake maste

cylinder that controls pressure to the rear wheels to achieve better braking balan

front-to-rear.

Pump A device used to transfer fluids or air by suction, pressure, or both. An example

this is an oil pump for the vehicle's engine, or the pump that raises and lowers th

pressure in a vehicle's air-ride suspension system.

Pushrod Pushrods are used in engines with overhead valve (OHV) designs. The camshaft

the engine block pushes up on the lifters and then on the pushrods, which then p

the rocker arms, which then open the valves.

R

Radial Referring to a type of air conditioning compressor that compresses its refrigeran

using a radial, or round, piston and cylinder arrangement. It's a fairly light unit

is associated with 1982 and newer GM vehicles and used R12 and R-134 refriger

Compare to Axial. (Remember, Axial is LONG like an axle; Radial is SHORT li


20/27

radial tire.)

Radiator A radiator is a liquid-to-air heat transfer device having a tank(s) and core(s)

specifically designed to reduce the temperature of the coolant in an liquid-cooled

internal combustion engine. Radiators can be made from aluminum or copper-b

Radiator cap The radiator cap maintains a specific pressure in the cooling system so it operate

efficiently.

Rail A manifold for fuel injection which distributes fuel to the fuel injectors, often cal

fuel rail. They are usually made from an aluminum extrusion or steel pipe.

Ram Air Type of induction where fresh air is fed through the hood or underneath the veh

and sent to the intake via the air filter. With the reduced air temperatures associ

with fresh, non-underhood, ram air, more power and efficiency is generated.

Rear-wheel drive

(RWD)

Rear wheel drive cars transmit power to the ground through the rear wheels.

Refrigerant Commonly referred to as freon, it is a substance used as a heat transfer agent in

air conditioning system. There are two types being used in vehicles today; R134 fnewer cars and R12 for older vehicles. Because R12 refrigerant is harmful to the

environment when it leaks into the atmosphere, it is being phased out in favor of

R134.

Regulator (Voltage) A device that automatically controls the output of another device by adjusting th

voltage to meet a specified value. Example: an alternator can put out over 14 vol

but by sending the voltage through a regulator, it only allows 12 volts output.

Relay A electromechanical device in which connections of a higher voltage circuit are

operated by a lower voltage circuit to divert the current. High-output auxiliary

driving lights contain relays in their circuits so as not to overload and burnout th

on-off switch.

Remanufactured A component or piece of equipment that has been rebuilt and restored to its OE

(original equipment) specifications to function as new. Common examples of reb

parts include alternators, water pumps, carburetors and power steering pumps.

Reservoir Reservoir is a generic term that refers to any container for a fluid. For instance,

vehicles have a windshield washer fluid reservoir and a brake fluid reservoir.

Revving the engine Increasing the RPM's of an engine without allowing the power to be transferred

the wheels. When your car is in park or neutral and you press on the gas without

intention of making the car move, you are revving the engine.

Rheostat Rheostat refers to a control which varies the intensity of the lights and speed of

certain accessories that it is connected to. For instance, an instrument lighting

rheostat controls the brightness of the instrument lighting.

Riding the clutch When driving along, if you rest your foot on the clutch pedal, you are riding the

clutch. This practice causes excess wear on the clutch and the clutch throw-out

bearing.

Rocker arms Rocker arms are used in overhead valve (OHV) engines. They are operated by

pushrods and open and close the valves.


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Roller Cam A camshaft which uses lifters, either hydraulic or mechanical, using rollers at th

base of each lifter which contacts the cam. These high-strength steel cams reduce

friction and emissions and increase power and efficiency with optimized lobe des

Rotary engine A rotary engine does not have pistons or cylinders; instead, it has triangular sha

rotors that move in an elliptical path within chambers to create power. The only

companies that have offered rotary cars for sale are Mazda, NSU, and Citroen.

Rotor- Brake A disc made from cast iron or steel, rotating on an integral or separate hub nearwheel of a vehicle and is stopped by friction pads located on either side of a

hydraulically-operated brake caliper.

Rotor-Distributor An electrically conductive component mounted to the rotating distributor shaft t

transfers electrical energy from the centrally located coil terminal to the individu

cylinder terminals within the distributor cap circumference. Also known as an

ignition rotor.

Rubbing compound A rubbing compound is a type of paint polish that contains extremely fine abrasi

particles. These particles remove the top layer of paint, eliminating shallow

scratches, and revealing the shiny paint layer underneath.

Running Board Usually a long, flat board that runs along the rocker panel of a truck or SUV, wh

is used to help passengers step in and out of the vehicle.

Running rich This is a condition that occurs when too much gas and too little air is being fed to

engine. A sign of rich running is black, sooty exhaust.

Rust-converting

primer

Rust-converting primer is a special type of primer paint that stops the progress o

surface rust.

S

Scan Tool A device that interfaces with, and communicates vehicle information to and from

vehicle's power train control module or computer, via an onboard data link.

Sensor The name for a device that senses the absolute value or a change in a physical

quantity such as temperature, pressure, rotation or flow rate, and converts that

change into an electrical signal, which is then sent to the vehicle's power train co

module (PCM).

Serpentine belt A serpentine belt is a wide single drive belt that drives certain engine accessories

(alternator, power steering pump, air conditioning compressor, etc.). It's a type ofan belt with multiple grooves that fit into similar grooves on the pulleys. Also kn

as a multi-groove belt, micro-groove belt, or multi-v belt.

Shift linkage This is a series of rods and/or cables that connect the gearshift lever or gear selec

to the transmission.

Shift Solenoid A PCM-controlled electromechanical device which regulates shift firmness and r

in an electronically-controlled automatic transmission.

Shock Absorber A component using friction to dampen and control a vehicle's suspension up and

down movement. Modern shocks are of the hydraulic type, using an oil to dissipa


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the heat of friction to the outside air. They contribute to your vehicle's ride quali

See also Strut.

Short (circuit) A short circuit occurs when there is a break in an electrical circuit and the circu

finds a new ground source.

Shroud A metal or plastic cover used to isolate rotating components or hot parts of the

vehicles' engine or exhaust system. A radiator shroud surrounds the radiator fan

helps direct incoming air through the radiator and to the front of the engine as was protecting the radiator and fan from foreign objects.

Single overhead cam

(SOHC)

A type of overhead cam engine with a single cam that operates both the intake an

exhaust valves.

Solenoid A device consisting of an electrical coil, and when energized, produces a magneti

field in a plunger and is pulled to a central position. A solenoid may be used as a

actuator in a valve or switch. Power door locks use a solenoid-activated actuator

Spark Plug Part of the ignition system, it's an electrical device with a ground and center

electrode where a spark is created between the two by a high voltage current fro

the distributor. The spark ignites the fuel/air mixture in the combustion chambethe top of the compression stroke.

Spark plug electrode The electrode is the curved piece(s) of metal (ground electrode) that reaches over

center electrode. The spark is created between the electrodes.

Spark plug gap Gap is the precise distance between a spark plug's center and ground electrodes.

Spark plug terminal The terminal is the metal part of a spark plug above the ceramic insulator that t

spark plug wire attaches to.

Spark plug wires Spark plug wires are the cables that conduct the electric pulses from the distribu

cap to the spark plugs. Also called ignition wires.

Speedometer An instrument that indicates a vehicle's speed in miles or kilometers per hour.

Sprag A transmission internal component load carrying element, usually consisting of r

bearings and a cage element. Heavy duty sprags have more bearings, therefore a

greater load capacity.

Springs (suspension) Springs absorb road imperfections and vibration, help hold the suspension up, a

help vehicles handle better. Also called coil springs, or leaf springs.

Stabilizer bar See Sway bar.

Starter motor

(starter)

This is the electric motor that turns your engine over when you turn the key in th

ignition switch.

Starter solenoid This is a large relay that controls the operation of the starter motor.

Starting system The starting system consists of the starter motor, starter solenoid, battery, igniti

switch and ignition key.

Steering lock The steering lock is a theft prevention device that locks the steering wheel in plac

when the key is removed from the ignition switch.


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Steering system The steering system allows you to control the direction of your vehicle. Most mod

cars have a rack and pinion steering system with a power assist. Components in

steering system include the steering rack, tie rods, tie rod ends, ball joints, power

steering pump, power steering hoses, and the pump drive belt.

Stroke The distance traveled by the piston in its cylinder from top dead center to bottom

dead center. The stroke is determined by the throw of the crankshaft, and is a

determining factor in the displacement of an engine.

Struts Struts are part of your vehicle's suspension, and do the same job as a shock abso

A vehicle will either have struts or shock absorbers, or a combination of both (i.e

struts in the front, and shock absorbers in the rear). They regulate how much yo

vehicle can move up and down, and keeps the tires in contact with the road surfa

after going over a bump.

Supercharger A mechanically driven device, usually off the crankshaft, that pressurizes the int

air, and in turn increases the density of the air/fuel mixture and subsequently

increases the power output of a given engine displacement.

Suspension The suspension connects the vehicle body to the frame. A well tuned suspension

the vehicle to handle better, while increasing comfort and isolating passengers frbumps and vibration.

Sway bar The sway bar is a suspension system component that helps to minimize the lean o

vehicle when cornering. Also called a stabilizer bar.

Synchromesh Synchromesh is a feature that allows you to upshift and downshift a manual

transmission without grinding gears. It does this by synchronizing, or evening ou

the speed of the engine and the speed of the gear you are selecting. If the

transmission didn't have synchromesh, you would either have to match the engin

speed to the gear speed (known as double-clutching) or else grind the gears every

time you shift. This term is often shortened to just "synchro".

T

Tachometer An instrument that indicates engine speed in revolutions-per-minute (rpm). It

measures the speed that the crankshaft is rotating.

Tailpipe The part of an exhaust system where exhaust gasses exit the car body from the r

of the vehicle. The tailpipe connects the muffler to the tailpipe tip (sometimes cal

spout). The tailpipe tip is the part of the exhaust system that you can see sticking

from under the rear bumper.

Thermostat The thermostat is a valve located in the cooling system of a vehicle that automati

regulates the coolant flow through the radiator and engine based on the coolant

temperature.

Throttle A mechanism for regulating the supply of the fuel/air mixture to an internal

combustion engine, thereby regulating the speed of the engine. Aka; accelerator

pedal

Tie rod Part of the steering system, the tie rod connects the spindles/wheels to the rest of

steering system.


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Timing (ignition

timing)

Timing refers to the moment when the spark ignites the air/fuel mixture in the

engine's combustion chamber. Timing needs to be set exactly right for an engine

run correctly.

Timing belt Timing belts are rubber belts that connect an engine's camshaft to its crankshaft

timing belt breaks, these two components will get out of synch, which can cause

potentially significant engine damage.

Timing chain Timing chains are metal chains that connect an engine's camshaft gear to itscrankshaft gear. Timing chains ride on sprockets that eventually wear out and ca

cause sloppy timing. When this happens, it is time to replace the sprockets and c

If a timing chain breaks, the camshaft and crankshaft will get out of synch, causi

potentially significant engine damage.

Timing gears Timing gears are part of a timing chain system that connects the engine's camsh

its crankshaft. On some vehicles, the camshaft gear meshes directly with the

crankshaft gear, eliminating the timing chain.

Timing light A timing light is used to check or set ignition timing.

Tire gauge Tire gauges are used to measure the air pressure of a tire. You should always ch

tire pressure when your tire is cold (when the vehicle hasn't been driven for abou

hour).

Tire valve The fitting in the valve stem of the wheel that allows you to inflate or deflate the

Tonneau An accessory cover fitted to protect a vehicle bed or driver's compartment, most

often on pickups and early autos. A tonneau can be constructed of fabric, metal o

fiberglass. In addition to sealing the vehicle bed or passenger area, it also contrib

to vehicle appearance.

Torque converter A fluid coupling device which multiplies torque between an engine and automatitransmission/transaxle. It allows smooth power transfer from the engine to the

transmission. When a vehicle is stopped, a converter allows enough fluid slippag

that the engine can idle without stalling.

Transaxle Transaxles are a combination of components; the transmission and differential.

front-wheel drive cars have transaxles. However, some rear wheel drive cars, suc

some Porsches, new Corvettes and Alfa Romeos, have rear-mounted transaxles.

Transducer A device that receives an electrical signal from one system and transfers it, often

different form, to another system. Example: the cruise control transducer conver

vehicle speed signal to a vacuum to control the servo attached to the throttle.

Transfer case Used in 4X4 vehicles to transfer power to the front and rear differential assembl

There are different selectable ranges to maximize traction in varying road or tra

conditions.

Transmission A component of the power train of a vehicle which selects gear changes (either

manually or automatically), which can increase or decrease the speed and power

between the engine and the drive axles.

Transmission fluid Transmission fluid (ATF) is specially developed to allow automatic transmission

operate smoothly and efficiently. Automatic transmission fluid needs to be check

and replenished periodically.


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Transmission

interlock

A safety device found on many modern automatic transmissions that prevents th

drive or reverse gear from being selected until the brake pedal is pressed.

Transmission linkage This is a series of rods and/or cables that connect the gearshift lever or gear selec

to the transmission, allowing the shifting of gears.

Transmission mounts Transmission mounts are often made of steel and rubber. Transmission mounts

support the transmission, and also help to prevent transmission vibrations from

being transmitted to the car interior.

Transmission oil Transmission oil is specially developed to allow manual transmissions to operate

smoothly and efficiently. Transmission oil rarely needs to be replenished.

Travel Travel is a measurement of how much movement, or play, occurs in a given syste

Trinary Consisting of three (3) parts, or a progression of a multiple of threes (3).

Tune up A procedure during which a series of parts that wear out (spark plugs, ignition r

distributor cap, etc.) are replaced to bring the engine back into proper operating

specifications. In addition, timing is normally checked and reset. A tune up is usu

performed according to a schedule.

Turbocharger A centrifugal device driven by exhaust gases that pressurizes the intake air,

increasing the density of the air and consequently increasing the power output fr

a given engine displacement. A turbocharger will boost the power of an engine.

U

Universal joint Universal joints are part of a car's driveline. They allow the driveshaft to continu

rotate at all angles.

V

Vacuum A condition in which pressure has been reduced below the ambient atmospheric

pressure. Vacuum is created in the intake manifold and can be used to operate a

power brake booster.

Vacuum hose Vacuum hoses connect between vacuum-powered accessories and a vacuum sour

such as the engine's intake manifold.

Valve A device by which the flow of a liquid, gas or vacuum may be controlled. Examp

the intake and exhaust valve in the cylinder heads start and stop the flow of the

incoming fuel mixture and outgoing combusted exhaust gases.

Valve cover The valve cover is the metal cover that is attached to the top of the cylinder head

allows technicians access to the engine valves and rocker arms for adjustment an

checks.

Valvetrain Components actuated by the camshaft and can include valve lifters, pushrods, ro

arms and valve springs.


26/27

Vapor lock Vapor lock occurs when an engine gets so hot, it boils the fuel traveling through

fuel lines. This creates vapor, preventing the fuel from traveling through the line

causing the engine to stop running.

Variable-assist power

steering

A power steering system designed to vary the level of power assist according to

vehicle speed or angle of the steering wheel.

VIN Code The VIN (Vehicle Identification Number) can be found by looking at the dashboard o

driver side of the vehicle. If the VIN cannot be found, open the driver side door and loat the door post (where the door latches when it is closed). It is likely that the VIN wi

also be displayed in this location.

Voltage regulator The voltage regulator limits the power output of the alternator to prevent

overcharging the battery and electrical system.

W

Washer fluid This is special fluid designed to help clean the windshield quickly and with little

residue, used in conjunction with the wiper blades.

Washer fluid

reservoir

The container where washer fluid is kept in a car, usually located under the hood

Washer nozzles These are the jets on the hood or in the wipers that spray washer fluid onto the

windshield.

Washer pump An electric motor that delivers washer fluid to the washer nozzles for cleaning th

windshield with the windshield wipers.

Wastegate A valve on a turbocharged engine that limits air pressure in the intake tract by

allowing the pressure to bypass to outside air, after the turbocharger.

Water in fuel warning

light

This is a warning light found only on diesel-engine cars. Because diesel fuel colle

water, a sensor in the fuel tank will indicate when the ratio of diesel fuel to water

reaches a certain level.

Water pump Part of the cooling system, the water pump circulates coolant, helping the engine

stay in the desired temperature range.

Wax Wax is a product used to protect paint finishes and create extra shine.

Weather-stripping A rubber gasket found around vehicle openings to seal out water and wind. Wea

stripping is located around doors, windows and trunks.

Wheel bearing A bearing or bearing assembly located at each wheel allowing the wheel to spin

around the axle with minimal wear and friction. Front wheel bearings are contai

within the hub, and are sometimes integral to the hub. A wheel bearing set consi

an inner and outer bearing.

Wheel cylinder

(brakes)

The wheel cylinder is used with drum-type brakes. When the brake pedal is push

the wheel cylinder pushes the brake shoes against the drum brake, slowing or

stopping the car.

Wheel nuts Wheel nuts are used to attach a wheel to a hub.


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Wiper arms The part of the windshield wipers that are between the wiper pivots at the base o

windshield and wiper blades.

Wiper blades The rubber part and carrier assembly of the windshield wiper that clears the

windshield.

Wiper refill The rubber part of the wiper blade that makes contact with the windshield. A w

refill will insert into a wiper blade.

Wire (electrical) An insulated conductor used in an electrical system to transmit electricity from o

component to another. If a wire breaks, it creates an open circuit. If a broken wi

make contact with a grounded surface, it creates a short circuit.

auto dictionary

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