Auto Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Click on Letters
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/or 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 pump circuit to allow the engine to deliver more power.
Accessory Refers to a power-operated feature on a car. For instance, power windows and power locks would be considered accessories.
Accumulator A container in the air conditioning system used to remove moisture or water. This helps to extend a/c compressor and other component life.
Actuator An electrical mechanism for moving or controlling something indirectly instead of by hand, such as a door lock. Output device the PCM controls such as solenoids, relays, fuel injectors and stepper motors.
Air Conditioning An Original Equipment or Aftermarket accessory system that cools and dries the incoming passenger compartment air. Aka: a/c
Air Filter This device filters the air that goes into your engine. Without an air filter, harmful 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 vehicle's exhaust to help complete the combustion process and reduce emissions.
Air Bag A safety device, consisting of impact sensors, computer, a detonation device and air bag, that protects the driver (and in some cases, the passenger) in a crash by inflating a cushion hidden in the steering wheel and dashboard.
Alignment Alignment is when all your wheels are pointing in exactly the right direction. If one 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 four wheels according to which have the most traction.
Alternator An alternator is an engine-belt driven device that converts mechanical energy into electrical energy. The electrical output keeps your battery charged and operates your 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 flat 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 radios, it 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 for your vehicle.
Automatic Choke Automatic chokes use either a heat- or computer-controlled element to turn on and off automatically as needed.
Automatic Temperature Control A computerized system that automatically maintains a selected temperature for your 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 the same pressure.
Balancing (Tire) The process of making sure a tire will not cause vibration when driving. By using a computerized machine, a technician can locate a non-balanced tire and balance it by 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 parts. 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 into 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 to 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 replaced 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 case. 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 provide 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 chime.
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 caliper or 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 the brakes for added stopping power.
Brake Caliper A c-shaped device used with disc brakes. When a driver presses on the brake pedal, the 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 brake caliper or wheel cylinder.
Brake Lines Metal tubing and rubber hoses which connects each brake caliper or wheel cylinder to 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 four 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 you step 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 plates that rotate with the wheel when you drive. When you step on the brake, the brake calipers squeeze the brake discs, slowing or stopping the car.
Brake Shoes Brake shoes are used specifically with drum brake systems. Brake shoes fit inside the brake drum, and are pressed against the drum by a wheel cylinder when the brakes 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 booster, brake master cylinder, brake lines, brake fluid, brake rotors (including calipers and pads), and, for some vehicles, brake drums (including wheel cylinders and brake shoes). In addition, all vehicles have a parking/emergency brake. Taken together, these components operate in sync to slow or stop your car. They operate like this: when you press on the brake pedal, the pressure you apply is multiplied by the brake booster. It is then distributed by the brake master cylinder and sent via the brake fluid through the brake lines to each individual wheel. When it arrives at a wheel, this pressure causes, for instance, the caliper (in a vehicle with disc brakes) to close, which then causes the pads to come in contact with the brake rotor. The resulting friction causes the car to slow down and eventually stop. Should this system fail, then the emergency brake may be used as a backup to stop your vehicle.
Burning Oil (Engine) Oil burning occurs when one or more internal engine components fail, thus allowing oil into the engine's combustion chamber. There, the oil is burned along with the air/fuel mixture.
Bushing A piece of rubber or plastic that fits in between two components. Bushing protects the two components from excess wear and damage.
Bypass Providing a secondary path to relieve pressure in the primary passage. One example would be a water pump or thermostat housing bypass in the cooling system.
C

Caliper The housing on disc brakes which holds the disc pads and straddles the brake rotor. When hydraulically actuated, the pads press against the rotor, or disc, to stop or slow the vehicles wheels.
Camber It's the adjustment of a wheels alignment where the top of the wheel is moved inward or outward from vertical as viewed from the front of the vehicle. Incorrect camber reduces tire life.
Camshaft A camshaft, with phased cam lobes mounted on it, regulates the opening and closing of the intake and exhaust valves. Driven by the crankshaft via a timing chain or timing belt, a camshaft has a big influence on engine power characteristics.
Canister An evaporative emission canister contains activated charcoal which absorbs fuel vapors and holds them until the vapors can be purged into the engine when it is started. It is a component of the emissions control system.
Capacitor An electrical device for accumulating and holding a charge of electricity. A capacitor is usually found in an electronic ignition system.
Carb See Carburetor.
Carbon Dioxide A heavy, colorless gas that results as a product of complete combustion. It is considered a greenhouse gas.
Carbon Monoxide A colorless, odorless gas that can be found as a product of incomplete combustion. Breathing high concentrations can be dangerous.
Carburetor A mechanism which mixes fuel with air in the proper proportions to provide a desired power output from a spark-ignition internal combustion engine. On 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 mixed 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 between 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 for 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 the body, fenders, etc.
Choke A device in a carburetor which shuts off airflow so that the engine runs rich. This is necessary to start a cold engine.
Circuit A complete electrical path, usually includes the electrical energy source. May also be used with fluids or air. The headlights and brake system are examples of an electrical and hydraulic circuit.
Cleaner (Air) A housing holding a filter fitted in the intake system of parts requiring clean air. An engine air cleaner filter removes particulates before they can enter the intake system and cause damage.
Clear-Coat Finish Many modern cars have a clear-coat finish. This is an extra, clear layer of paint that 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 controls. 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 loop system allows pre-programmed engine adjustments to occur while running in order to minimize exhaust emissions.
Clutch A mechanical device which uses mechanical, magnetic, or friction type connections to 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 fork to control clutch engagement.
Clutch - Hydraulic A hydraulic clutch uses a hydraulic circuit between the clutch pedal and clutch fork to control clutch engagement.
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 disengage with minimum wear.
Clutch-Operated Fan An engine cooling fan that uses a heat-activated, viscous-fluid clutch which turns the fan on and off as needed.
Code A system of symbols (as letters, numbers, or words) used to represent the meaning of 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 to step up battery voltage. The high voltage created (35,000 volts or more) is delivered to the spark plug so ignition can occur.
Coil Spring A spiral-wound steel wire coil, of various wire diameter thicknesses and coil stack heights, used to suspend a vehicle. Can be used in cars and trucks, both front and rear, depending on the application.
Combustion The process by which the air/fuel mixture burns within an engine to create power.
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 can 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) or powertrain control module (PCM). This controls the car's fuel and ignition systems by taking information from various sensors to determine how to run the engine with the most efficiency and power.
Constant Velocity Joint A coupling that allows a shaft to turn continuously at various angles when coupled with another shaft. Usually associated with front-wheel or all-wheel drive vehicles.
Converter (Torque) A fluid coupling device which multiplies torque between an engine and automatic transmission/transaxle. When a vehicle is stopped, a converter allows enough fluid slippage, 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 vehicle coolants are designed to last 100,000 miles. Please refer to your owner's manual for the proper antifreeze for your vehicle.
Coolant Reservoir Many cars have a clear plastic reservoir that allows the owner to see the level of their vehicle's coolant. Check your owner's manual to find the coolant reservoir on your vehicle.
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, and antifreeze.
Core (Price/Charge) A payment that is credited back to the buyer after they have returned a rebuildable ôCoreö unit to the retailer. A rebuilt alternator purchase would have a core charge and 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 spiderweb fashion across the surface of the paint. Cracked paint is unrestorable, and must often be completely removed when a car is repainted.
Crankshaft The engine component which converts piston reciprocating (up and down) motion 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 hairline cracks. These cracks may spread in a spiderweb fashion across the surface of the 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 little 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 occurs. This 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, it contains the camshafts as well. A head is an important influence in determining an engineÆs overall power and efficiency.
D

Data General term for information, usually represented by numbers, letters and symbols. 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 from your vehicle's windows.
Diagnostics The process of identifying the cause or nature of a condition or situation. Most cars have computer diagnostic systems that help the technician to determine corrective repairs.
Diesel Engine A type of engine that uses heat caused by engine compression rather than spark plugs to ignite its fuel mixture. Diesels are often more economical than gasoline engines, however they create extra noise and vibration.
Dieseling The continued running of a spark-ignited engine after the ignition is turned off. There are two basic causes of dieseling: surface ignition, where combustion chamber surfaces remain hot enough to ignite fuel after the spark is terminated; compression ignition, where the conditions of temperature, pressure, fuel composition and engine idle speed allow ignition to continue.
Differential A component of the drivetrain with an arrangement of gears designed to permit the division of power between two shafts. A differential also lets two wheels on the same axle rotate at different speeds. With out one, cars wouldn't be able to take sharp turns. Differentials are located in a drive axle housing.
Distributor Part of the ignition system, its a mechanical device designed to direct high voltage electricity from the coil to the spark plugs, via the spark plug wires. Rotating the distributor permits adjustment of an engine's initial ignition timing.
Distributor Cap The distributor cap contains the terminals that the spark plug wires plug into. When the distributor sends power to a spark plug, it goes to the cap first and then to the spark plug wire and to the spark plug.
Distributor Rotor The rotor spins around inside the distributor. As it turns, it comes close to the terminals for each spark plug on the distributor cap. When this happens, it sends current to the spark plug, which then ignites the air/fuel mixture in the cylinder at exactly the right time.
Double Overhead Cam (DOHC) A DOHC engine has two camshafts in the cylinder head - one for the exhaust valves, and one for the intake valves. This allows greater efficiency and greater power.
Downshifting The process of going from a higher gear (for instance, fourth gear) to a lower gear (for instance, second gear) with a manual or automatic transmission.
Drive Belt Also called a fan belt or serpentine belt, drive belts are used to drive the engine's accessories, such as the alternator, power steering pump, and air conditioning compressor. A serpentine belt is a wide single drive belt that drives several the engine's accessories at once.
Driveline The system of components that connects the transmission to the wheels. The driveline consists of axles, differentials, constant velocity (CV) or universal joints, and a driveshaft.
Driver A switched electronic device housed in a computer that controls output state. For example, a driver controls how long a fuel injector remains open.
Driveshaft The shaft connecting the transmission output shaft to the differential pinion shaft. It transmits power from the transmission to the differential. It is found primarily on rear-drive vehicles. There is usually a universal joint on either end.
E

Early Fuel Evaporation Used on carburetor-equipped engines only, a system where heat is used to help increase early fuel evaporation of the cold-start air/fuel mixture to achieve more 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 main hydraulic system. It can be used to slow or stop the vehicle if the primary brakes fail, or to hold the vehicle stationary though the brake pedal is not depressed. It usually 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, water, 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 converter, air pump, and oxygen sensor.
Engine A machine designed to convert thermal energy into mechanical energy to produce force or motion. Connected to a drivetrain, an engine's mechanical energy, or torque, 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 the 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 conditioning compressor, as well as many others.
Engine Block The engine block is where the cylinders and pistons reside. The block is the strongest part 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 support the 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 light and engine temperature gauge, respectively. Compare to coolant temperature sensor (CTS) which transmits the coolant temperature to the computer, and the radiator 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 the 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 of nitrogen emissions. The EGR system is important for a smooth performing engine.
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 either a motor or belt.
Fan Belt Also called a drive belt or serpentine belt. Fan belts are used to drive the engine's accessories, such as the alternator, power steering pump, or air conditioning compressor. A serpentine belt is a wide single drive belt that drives multiple engine 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 feeler 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 unable 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 numerically high ratio enhances vehicle acceleration and pulling ability, while a numerically low 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 connection between the transmission torque converter and the engine allowing flexing. Compare 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 connection between the transmission clutch and the engine. Compare to flexplate for automatic transmission.
Four-Wheel Drive (4WD) A drive system in which both the front and rear wheels are connected through the driveshaft and axles to the transmission, usually via a transfer case. A 4WD sytem 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 of the car.
Fuel Any combustible substance burned to provide heat or power. While gasoline is the 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 the carburetor or fuel injection system.
Fuel Injection Fuel injection is a system by which fuel is directly sprayed into the intake manifold 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 individual cylinders. An injector sprays fuel, which helps atomization for a more dense mixture, when 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 cylinder. The fuel system includes the fuel tank, fuel tank level sending unit, the fuel pump, the 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, fuel pressure 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 to 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 destroyed when the circuit is subjected to a power overload. This is a non-reversible action and there are 3 main types of fuses; glass, ceramic and spade.
G

G-Force Unit of measurement used to describe ôlateralö acceleration generated while the vehicle is driven in a steady state turn on a skid pad circle. An average sedan generates 0.60 G of lateral acceleration. Measured in "gravities", one G equals the earth's gravity at 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 are "regular" for low-grade gas, and "premium" for high-grade gas.
Gasket A material usually made of rubber, cork, metal, paper or a combination thereof that 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 system. 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 automatic transmission. In modern cars, the gear selector is often connected to the brake pedal, 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 the 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 gears 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 selector to the transmission.
Generator A generator is like an alternator in that it generates electrical current to both keep the battery charged and supply electricity for a vehicle's electric system. It differs 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 pipe (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. Glazing occurs when the belt slips repeatedly at a high speed. It is a sign that the belt needs replacement.
Glow Plug A combustion chamber heat generating device to aid starting diesel engines. When the glow plug heats the combustion chamber to the proper temperature, the ignition 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 either end, being driven from a differential. Also called a CV axle.
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 flow 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 the heater is turned on, it opens the heater valve which lets hot coolant into the heater 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 interior of the vehicle.
Heater Fan The heater fan is the interior fan attached to a blower motor that controls the speed of air being introduced into the interior.
Heater Valve The heater valve is controlled by the interior heating controls. When you turn on your vehicle's heater, the valve opens and allows hot coolant to enter the heater core, which then warms the air forced through the heater core by a blower motor, and the 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 core, 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 fasteners with hexagonal openings.
Hoses (Cooling System) The cooling system hoses allow coolant to circulate between the radiator, engine, and heater. Over time, they deteriorate, and should be checked annually for condition 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 by 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 efficiently in the cylinders, hydrocarbon molecules are released into the atmosphere as pollutants.
I

Idle Running engine speed with vehicle at rest and accelerator or throttle pedal not 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 the engine is at an idle.
Ignition Complete system used to step up battery voltage to a higher voltage and deliver it to the spark plug to complete the combustion process. When the key is turned on, the ignition system is energized.
Ignition Advance/Retard The advancing or retarding (in crank degrees) of ignition spark relative to the piston 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 system that has points. This prevents that extra energy from jumping across the points when 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, which opens and closes the electric circuit. Electronic ignition systems have made ignition 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 spark plugs. These include the battery, the ignition coil, the distributor (including the cap 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 individual cylinders. A fuel injector sprays fuel, which helps atomization for a more dense mixture, when combined with incoming air.
Instrument An instrument measures levels of a certain system and provides a visual key for those 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.
J

Junk The neighbor's Car.
K

Knock (Engine) The sharp, metallic sound produced when two pressure, or flame fronts collide in the 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 to its increased resistance to cylinder pressure.
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 interior of a brake drum.
Leaf Spring A thin, long, arched, steel spring that is attached between a vehicles frame and axle to act as a suspension. More than one spring leaf are often clamped together to achieve 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 holds pressure. If a cylinder is unable to hold pressure, your technician can pinpoint what component of the cylinder (piston rings, valves, etc) has the problem that is causing the pressure loss.
Liability Insurance Liability insurance is coverage only for damage that you inflict on other people or 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 wheel with the most grip. Many high-performance vehicles have LSDs.
Link (Electrical/Electronic) General term used to indicate a communication connection between two data points. 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 from 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 such 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 directly above the upper control arm. Many lightweight, uni-body cars use this uncomplicated type of front suspension.
Main Bearings Soft metal alloy inserts, bonded to a steel back, used to allow the crankshaft to ride 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 instead of manual chokes.
Manual Steering With a manual steering system, there is no power assist to the driver.
Manual Transmission A manual transmission is a transmission with a clutch. In addition, it is up to the driver to select gears.
Memory A device in which data can be stored and retrieved when needed; associated with a vehicle's computer system.
Mode One of several alternative conditions or methods of operating a system, device or control module. If a vehicle has a 3-mode electronic adjusting shock absorber system, the modes (or settings) are usually soft, medium, or firm.
Module (Electrical/Electronic) A self-contained group of electrical/electronic components, which is designed as a single replaceable unit. An example of a module is the one that operates the anti-lock braking system.
Muffler The muffler is a part of the exhaust system designed to reduce the noise generated by a vehicle.
N

Neutral (Gear) Neutral is actually not a gear. When your vehicle is in neutral, the gearbox (transmission) and engine are completely disconnected. Thus, your car is able to roll freely whether the engine is on or off.
O

Octane A fuel octane rating measures a fuel's resistance to knocking or pinging. The higher the octane rating, the better (and more expensive) the fuel.
Odometer The odometer measures how many miles your vehicle has traveled.
Oil Filter The oil filter removes most particles and contaminates from your engine's oil to protect your engine's internal moving parts.
Oil Pan The oil pan is where the oil in your engine is stored.
Oil Pressure Sensor The oil pressure sensor measures the pressure at which your engine's oil is flowing. If the pressure becomes too high or too low, the oil pressure sensor sends a signal to the vehicle's oil pressure warning light located on the dashboard. If you see this light turn on, pull over as soon as possible and shut off your engine. Check the oil level of the engine by pulling out the dipstick. If the engine oil level is low, add oil, restart the vehicle and see if the oil light goes out. If the oil level is within parameters, or the oil light remains on, have your car towed to a service facility to have the problem checked by a technician.
Oil Pump The oil pump takes oil from the oil pan and pressurizes it, allowing it to travel throughout the engine and lubricate the engine's moving parts.
Open Loop An operating condition or mode in the vehicle's intake fuel system controlled by the vehicle's PCM, based on pre-programmed instructions, usually when an engine is in the cold start-up mode.