Glossary Terms Between A and D
accelerator Otherwise know as the gas pedal, it is the pedal that makes the car go faster the further it is depressed.
air cleaner A metal or plastic housing near the fuel injection intake where the air filter sits. The filter removes large particles from the air before entering your engine.
air filter This filter sits inside the air cleaner to remove large particles from the air before entering your engine.
air pump A device that pumps air into the exhaust system to cut down on the level of unburned fuel in the exhaust.
alignment The position of the wheels relative to the car body. Proper wheel alignment reduces tire wear and improves driving control. Normal driving will eventually take wheels slightly out of alignment but running over bumps and curbs will make that happen faster. Cars have adjustments that allow mechanics to bring wheels back in alignment.
all-wheel drive A vehicle on which the power is delivered to all the wheels versus the more common 2 wheel drives on which power is delivered only to the front or rear wheels. Full-time all-wheel drive operates constantly and improves handling even on dry pavement. Selectable all-wheel drive is engaged manually at the driver's discretion.
Allen wrench An L-shaped tool that works like a screwdriver, designed to remove screws with hexagonal holes in their heads. They are sometimes called hex wrenches.
alternative fuel A substance other than gasoline or diesel fuel, such as electricity, natural gas, hydrogen, and fuel cells.
alternative power plants Hybrids, fuel cells, and other innovations designed to replace the internal combustion engine.
alternator An electric generator for your car. As you drive, it generates electricity that's stored in the battery to be used in starting the car and running the electrical equipment.
anti-lock braking system (ABS) Advanced technology designed to prevent brakes from locking up regardless of brake pedal pressure. Anti-lock braking systems have become increasingly popular because they enhance traction in slippery conditions and allow you to keep steering control of a vehicle, even in a skid.
antifreeze A greenish-yellow or orange colour chemical used to keep your engine at a normal operating temperature. It is usually mixed with water and circulated throughout your engine by a water pump to keep the engine from boiling as well as freezing. Most antifreeze also prevent rust and lubricate moving parts in the cooling system.
automatic choke A device that automatically adjusts the amount of air entering the carburetor by sensing changes in engine temperature. It is operated by a thermostatic spring that cuts air flow into a carburetor when the engine is cold.
automatic transmission A transmission that selects gears automatically based on the power required in various driving situations and conditions.
axle A solid metal shaft to which the wheels of a vehicle are attached on which they rotate.
backflushing Pushing fluid in a direction opposite of normal flow. This is done for cleaning purposes.
ball joint A movable joint found on the steering linkage and suspension system of a car that permits rotating movement in any direction between the parts that are joined.
bands Part of a system that allows an automatic transmissions to change gears.
battery A box filled with a solution of water and acid that stores electricity generated by the alternator. It deliver power to the parts of the car that operate on electricity.
bearings Anti-friction devices that are usually found between two moving parts to help movement while preventing wear . Bearings are found in ball- or roller-type.
biocide A product that kills any fungus or microbes that may have contaminated diesel fuel.
bleeding a system To remove air bubbles from a brake system, fuel injection system, or a cooling system so that they don't impede the flow of liquid through that system.
block heaters Devices that keep the engine warm when a car sits idle in very cold temperatures. These are especially important for starting diesel engines at extremely low temperatures.
blow-by Gases that blow past the piston rings during a piston's power stroke. These products form acid and sludge in the crankcase and cause smoke.
blue/black books A name for some popular listings of the current car prices, based on age, condition, and optional equipment; published in the Kelly Blue/Black Book, the NADA Used Car Guide (published by National Automobile Dealers Association), and the Red Book (published by National Market Reports).
boots The protective rubber cover of ball joints and constant velocity (CV) joints that holds grease. It also refers to the rubber or plastic covers located at either end of a spark-plug cable to insulate the connections between the cable ends and the spark plug and distributor terminals.
bore The width or diameter of the cylinder hole where gas is burned and pistons are pushed.
brake backing plate A metal plate, located inside the brake drum, on which the wheel cylinder, brake shoes, and other brake parts are mounted.
brake booster If your car has power brakes, a brake booster is located between the brake pedal and the master cylinder to increase the force applied to the brakes. There are two common types
brake calipers The clamp like device on a disc brake system that squeezes the brake pads onto the brake disc to slow down or stop the car.
brake discs Also known as rotors, these are used universally on front braking systems and on some rear braking systems. Brake fluid under pressure pushes pistons in brake calipers, which clamp a set of brake pads around one corner of the rotating disc and slow it down, thus slowing down the car.
brake drums Part of the braking system, these are metal drums mounted at the rear wheels on some cars. The brake shoes press against the inner surfaces of the drums to slow or stop the car. See also brake system.
brake fluid The liquid used in the hydraulic brake system to stop or slow the car. See also brake discs, brake lines.
brake lines A system of hoses and metal tubes through which the brake fluid flows from the master cylinder to the brakes at each wheel. See also brake system.
brake lining For drum brakes, this is high-friction and heat resistant material that's attached to a brake shoe. When the shoe is pressed against the brake drum, the lining grabs the inside of the drum, which stops the wheel and thus the car.
brake pads For disc brakes, these are friction material on a metal backing plate that, during braking, is clamped around a brake disc by brake caliper pistons to slow down the wheel to which it is attached. See also brake system, brake fluid.
brake shoes Curved pieces of metal on which brake linings are bonded. The shoes push the lining against the brake drum in order to slow and stop the car.
brake system A system that starts with your brake pedal and finishes with your brake pads. It uses hydraulic pressure to enable your car to slow and stop safely as you step on the pedal. It consists of all the parts, when you step on the brake pedal, that work together to force brake fluid in the master cylinder, through the brake lines, and into the calipers / cylinders in the disc or drum brakes at each wheel.
breaker plate In older cars with points and condensers, this is the movable plate inside the distributor to which the points and the condenser are affixed.
bushing A protective liner that provides a cushion between moving metal parts.
butterfly valve On non-fuel injected engines, this is a small metal disc that controls the flow of air into the carburetor.
calipers The clamp mounted on disc brakes that hold the brake pads and presses them against the disc to stop or slow the car.
cam An egg shaped metal lobe used in the camshaft to activate the opening and closing of the valves and, in the distributor, to force the points to open.
cam lobes The bumps on a camshaft that contact and activate cylinder head intake and exhaust valves, either directly or via such devices as camshaft lifters or push rods.
camber A wheel alignment adjustment of the inward or outward tilt on the top of the wheel when viewed from the front of the car. Improves handling and reduces tire wear.
camshaft A shaft with cam lobes that causes the valves to open and close. See also cam, overhead camshaft, push rods, rocker arms.
camshaft sensor A trigger device found on some distributor less ignition systems that synchronizes when the proper ignition coil should be fired.
carbon monoxide A colourless and odorless gas that is emitted as a byproduct of burning gasoline. This poisonous gas is emitted by the exhaust system of your vehicle.
carburetor Used in older cars, this is a complex device usually found right below the air cleaner that uses a series of flaps and valves to vapourize fuel and mixed it with air in proper quantities to suit the varying needs of the engine.
carburetor barrel The tube-like part of the carburetor through which air flows and is mixed with vapourized fuel. The choke butterfly valve is located at the top of the carburetor barrel, and the throttle valve is located at the bottom. The size and quantities of barrels dictate the volume of air that will enter the car's combustion chamber.
caster The forward or backward tilt of a car's front wheels that, when aligned properly, will make them follow naturally in a straight line. The caster setting is what helps the car return to straight after turning a corner.
catalytic converter Part of the exhaust system, this pollution-control device found on many newer cars it re-burns unburned gas in the exhaust system before it leaves your vehicle as exhaust.
centrifugal advance A device that is part of a non electronic distributor and advances or retards the ignition spark to correspond with changes in engine speed and load.
cetane rating Similar to octane in gasoline, this is a diesel oil rating based on the time lapse between fuel injection and ignition to determine how easily the oil ignites and how fast it burns. See also octane rating.
charging system The electrical generation and distribution system in your car. It includes the belt driven alternator (or generator) to generate electrical current and the battery which stores and delivers electricity to devices in the car.
chassis The underlying frame of a car. Or in other words, what is left when the fenders and body are removed.
chock A small block that is used to block a wheel from rolling. This keeps the vehicle from moving while working underneath it.
choke The device that regulates the amount of air allowed to enter the carburetor. When closed, it enriches the fuel/air mixture and enables the car to start and run more easily when cold. Automatic chokes have a thermostatic coil or thermostatic spring that activates a butterfly valve at the top of the carburetor barrel. Older cars have manually operated chokes.
cloud point The lowest temperature at which diesel oil tends to thicken and cloud up.
clutch Any device that connects or disconnects power transfer in rotating parts. In a manual transmission, this pedal operated device disconnects the engine from the transmission to allow the car to change gears, and then allows the engine and transmission to resume contact and turn together at a new speed. Clutches are also used in automatic transmissions, air conditioners, and differentials.
clutch disk In a manual transmission, this is the spinning plate located at the end of the driveshaft facing the engine and covered with an organic material surface. When the clutch is engaged, the clutch disk is gradually forced against the flywheel, causing the engine and the transmission to turn at the same speed with a smooth transition.
clutch pedal On cars with manual transmissions, this is a pedal ("The third pedal") located on the floor of the car to the left of the brake pedal. When the clutch pedal is depressed, it disengages the clutch so the driver can change gears.
coil A device used to amplify the voltage from a typical battery into a big jolt of voltage capable of jumping a spark plug gap. The jolt is distributed via the distributor and sent to the spark plugs.
coil springs Large metal coils that cushion and absorb the shocks and bumps as the car is driven. They work with the gas filled shock absorbers to keep the car on an even keel while giving you the smoothest ride possible.
combustion The burning of the fuel/air mixture that causes an explosion in the combustion chamber generating the power in an engine.
combustion chamber The part of the cylinder within an engine block where the fuel/air mixture is compressed by the piston and ignited by a spark from the spark plug.
compression gauge Like a tire gauge, this tool is used to check the maximum pressure created in a cylinder when the piston is at its highest point (TDC) and is squeezing the fuel/air mixture into the smallest possible space. Poor, or low compression, indicates leakage which leads to a loss of power from that cylinder.
compression ratio The ratio between the two volume extremes of the combustion chamber. This cylinder's cubic volume is measured when the piston is at the top (Top Dead Center) and the bottom of its stroke. The higher this ratio, the higher the octane rating required by your engine to prevent pre-ignition (or engine knocking) under load.
condenser A small metal cylinder, usually located inside a non-electronic distributor, that prevents electricity from arcing across the gap when the points are open by acting as a "sponge" for the excess current.
connecting rod The metal rod that connects the piston to the crankshaft and converts the up-and-down motion of a piston into the circular motion of the crankshaft. Under tremendous load and extensive wear, the rod can break and break through the engine block. This is called "throwing a rod".
constant velocity joints (CV) Found mostly in front-wheel-drive cars, and on some rear-wheel-drive cars with independent rear suspension systems, these special joints transmit engine power while allowing full steering and suspension movement. They are covered by black accordion boots that protect joints and hold grease.
control arms The upper or lower A shaped suspension components that are mounted on the frame and support the ball joints and steering knuckles.
coolant A solution that raises the boiling point and lowers the freezing point of the water in the cooling system, prevents rust and corrosion, and lubricates the system components. It is often called antifreeze.
coolant recovery system A bottle or tank that acts as a reservoir for liquid expelled from the cooling system through the overflow pipe and then returns the liquid to the system when it cools down. A special radiator pressure cap is also part of the system. Also called a closed cooling system when it's part of the original equipment.
cooling system The system that stores and circulates coolant throughout the engine (in water cooled engines only) to prevent overheating. Some cars have air-cooled engines in which air rushing by metal heat dispensing plates are sufficient to keep the engine cool.
core charge Core is an acronym for Cash On REturn. A sum of money is refunded for a re-buildable part that's exchanged for a rebuilt part of the same type. A common CORE charge is for brake shoes that need relining.
core plugs Metal plugs in the sides of the engine block that pop out because of excessive pressure. This prevents the engine block from cracking in freezing conditions. These plugs sometimes develop leaks and should then be replaced.
cotter pin A locking device shaped like a pin but split up the center. It's usually inserted in a hole drilled through a nut and bolt and is intended to lock the nut in place so that it can't unscrew. After insertion, the legs of the cotter pin are bent around the nut to keep it in place.
crankcase The lower part of the engine block that houses the crankshaft and its surrounding parts. The car's oil pan, into which the drain plug is screwed, is attached to the crankcase.
cranking The act of engaging the starter by turning the key in the ignition switch, which makes the engine turn over. In the old days, a hand crank was used to do this, hence the term cranking.
crankshaft The main rotating shaft in an engine that transfers the pistons' up and down motion into a smooth circular motion that is then used to drive the transmission and eventually the wheels.
crankshaft pulley A grooved wheel attached to the front end of the crankshaft which is connected by accessory belts to the fan, alternator, power steering pump, water pump, air conditioning compressor, and other devices so that the rotating crankshaft can drive these other parts as well. The crankshaft pulley usually has timing marks located on it, and these are necessary for checking and adjusting timing with a timing light. Also called a harmonic balance wheel.
crankshaft sensor A trigger device that tells the ignition module when to fire the spark plugs on cars with distributorless ignition systems.
creeper A platform on wheels that allows you to move around easily while lying on your back when you work under your car.
cross-shaft lug wrench See lugwrench.
cruise control An optional feature that keeps your car cruising at a preset speed unless overridden by the brake pedal.
CV joint Also Constant Velocity joint. Found mostly in front-wheel-drive cars, and on some rear-wheel-drive cars with independent rear suspension systems, these special joints transmit engine power while allowing full steering and suspension movement. They are covered by black accordion boots that protect joints and hold grease.
cylinder A hollow tube-shaped pipe in the engine block. The piston rides up and down in the cylinder to compress the fuel/air mixture that drives the engine.
cylinder block See engine block.
cylinder head The part above the engine block that contains the combustion chambers and the valves. The spark plugs screw into the top or side of the cylinder head. On most cars, a valve cover, camshaft cover, or a rocker-arm cover is located on top of the cylinder head.
cylinder sequence The order in which the cylinders are located on a particular car. It's necessary to locate the #1 cylinder to check and adjust timing with a timing light. The #1 cylinder may be at the front of the engine on a U.S.-made straight 4- or 6-cylinder engine or at the rear of the engine on a foreign-made car.
DEX-COOL A coolant that raises the boiling point and lowers the freezing point of the water in the cooling system, prevents rust and corrosion, and lubricates the system components. It is often called long-life antifreeze. It is orange in colour and is designed to function up to 60 months or 240,000 Kilometers.
diesel engine An engine that burns diesel fuel instead of gasoline. The diesel oil is injected directly into the combustion chamber, where it's ignited by the heat caused by intense compression, rather than by a spark from a spark plug.
diesel fuel Fuel for cars with diesel engines. It is heavier than gasoline and uses the heat of extremely highly compressed air to ignite the fuel in the combustion chamber.
dieseling This is the term used to describe an engine that continues to run after the ignition key has been switched off. This condition is often due to using fuel with too high an octane rating.
differential A component of gears, situated in rear-wheel drive cars between the rear wheels, that translates the power of the rotating driveshaft to drive the rear wheels. In front-wheel drive cars, the differential is located in the transaxle, usually directly below the transmission. The differential also allows each of the opposing wheels to turn at a different speed when cornering.
dipstick A stick that's dipped into a reservoir to check the level of the fluids based on the markings on the stick. Most common dipsticks are for used to check oil, transmission fluid, and power steering fluid.
disc brakes A brake system, that looks a lot like traditional bicycle brakes, that applies caliper pressure against a disk on wheels ( called rotors) to stop a car. Older cars have disc brakes on the front wheels and drum brakes on the rear wheels. Many of the new cars have disc brakes on all four wheels.
displacement Usually refers to the combined volume of the piston chambers - that is, the maximum volume of fuel and air that an engine can hold before compression takes place.
distributor A device that distributes an electric charge to the spark plugs via a piece of metal that rotates to reach sequential contact points. The rotating action is timed with the rotation of the engine in order to distribute an electric charge to the right spark plug, at the right time, and in the right sequence.
distributor cap A cap that covers the distributor. It has an outlet for each spark plug wire, plus an outlet where the wire from the coil enters the cap to conduct electrical current to the rotor. The cap keeps dirt and moisture from getting into the distributor.
distributor shaft The metal shaft inside the distributor that turns with the engine and in turn spins the distributor rotor.
distributorless ignition An ignition system in which each spark plug has its own high voltage source (or coil). Spark commands are issued from the engine management computer.
double overhead cam An engine that uses two camshafts mounted on the head to control the intake and exhaust valves respectively. This eliminates the need for pushrods to open and close valves.
downshifting A technique referring to manually shifting to a lower gear to accelerate or provide more power. This technique is also used in braking to assist the brakes in slowing down the vehicle.
drive train A term referring to all the components along a path of power from the engine to the drive wheels. It consists of the clutch, transmission, driveshaft, differential, transaxle, or rear axle.
drive wheels The set of wheels that actually propel the car forwards and backwards. Vehicles are now identified as having front-wheel drive, rear-wheel drive, four-wheel drive, or all-wheel drive.
drivebelt The belt that transfers the rotation of the engine via the crankshaft pulley to drive the various devices such as alternator for electricity, water pump for the cooling system, air conditioning compressor for your air conditioning, or power steering pump for your steering system.
driveline The shaft and joints that connect the transmission with the differential.
driveshaft A spinning metal shaft that transmits power from the transmission to the differential, the axle, and the drive wheels.
drum brakes Brake systems, usually mounted on back wheels, that force curved brake shoes against the inner walls of a hollow metal drum attached to each wheel.
dual carbs Two carburetors on the same engine allowing more fuel and air mixture to enter the engine..
dwell Refers to the number of degrees a distributor shaft rotates while ignition points are closed. Also called cam angle.
dwell meter A device for determining whether your points are correctly gapped in a nonelectronic ignition system.
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