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Radiator Glossary of Terms
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| Caliper |
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A hydraulically activated device in a disc brake system, which is mounted straddling the brake rotor (disc). The caliper contains at least one piston and two brake pads. Hydraulic pressure on the piston(s) forces the pads against the rotor.
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| Camber |
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The angle between the centerline of the tire and a vertical line as viewed from the front.
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| Camber Bolt |
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A bolt fitted with an eccentric that is turned to change a wheel's camber setting. Camber bolts are typically used on control arms and lower strut mounts.
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| Camber Roll |
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The change in camber that occurs when the front wheels on a vehicle with an independent suspension are steered to either side. The amount of camber change that occurs is affected by the amount of caster. Some camber change is good because it causes the ti
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| Camber Thrust |
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A cornering force generated by the tire's camber.
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| Camber Wear |
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Tire wear that occurs on one side of the tread because the tire is leaning in or out. The underlying cause may be worn control arm bushings, a weak or sagging spring or a badly worn ball joint.
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| Camshaft |
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A shaft in the engine on which are the lobes (cams) that operate the valves. The camshaft is driven by the crankshaft, via a belt, chain or gears, at one half the crankshaft speed.
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| Capacitor |
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A device that stores an electrical charge.
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| Carbon Dioxide (Co2) |
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A harmless, odorless gas composed of carbon and oxygen. It is the byproduct of complete combustion. But it is also a greenhouse gas that contributes to global warming.
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| Carbon Monoxide (CO) |
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A colorless, odorless gas given off as a normal byproduct of combustion. It is poisonous and extremely dangerous in confined areas, building up slowly to toxic levels without warning if adequate ventilation is not available.
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| Carburetor |
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A device, usually mounted on the intake manifold of an engine, which mixes the air and fuel in the proper proportion to allow even combustion.
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| Combination Valve |
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A device used in some fuel systems that routes fuel vapors to a charcoal storage canister instead of venting them into the atmosphere. The valve relieves fuel tank pressure and allows fresh air into the tank as the fuel level drops to prevent a vapor lock
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| Composite Headlight |
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A headlight system in which the bulb can be replaced without removing the whole unit.
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| Compounding |
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The combining of five basic ingredients: rubber, carbon black, plasticizers, curing materials, and ozone retardants to form the tread and other "rubber" components of a tire.
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| Compression Ratio |
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The comparison of the total volume of the cylinder and combustion chamber with the piston at BDC and the piston at TDC.
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| Compressor Cutoff Switch |
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See Thermostatic Switch.
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| Compressor Cycling Switch |
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See Thermostatic Switch.
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| Computerized Engine Controls |
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A microprocessor based engine management systems that utilizes various sensor inputs to regulate spark timing, fuel mixture, emissions and other functions. Used on most vehicles since 1981 to comply with federal emission regulations. Diagnosis usually req
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| Cardan Joint |
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Also known as a Hooke Joint, Universal Joint or U-Joint, it is a simple flexible coupling using a double yoke and four-point center cross. Cardan joints are used as couplings in the driveshafts of rear-wheel drive cars. Because they can produce uneven sha
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| Casing |
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The tire body, composed of plies that form the tire's structure and give it shape. Sometimes called the carcass.
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| Caster |
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The angle between the vehicle's steering axis and a vertical line, as viewed from the side.
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| Caster Shims |
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Small wedge shaped shims that fit between a leaf spring and solid axle to change caster. Used primarily on trucks with a solid front axle or four-wheel drive.
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| Catalytic Converter |
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A device installed in the exhaust system, like a muffler, that converts harmful byproducts of combustion into carbon dioxide and water vapor by means of a heat-producing chemical reaction.
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| CCMC |
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Committee of Common Market Automobile Constructors. Organization that established the limits and test criteria required for lubricants in the European market. Replaced by the ACEA in 1990.
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| Center Bolt |
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The bolt that maintains the alignment of the leaves in a leaf spring, and the position of the axle on the springs.
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| Center Link |
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The center bar or link in a parallelogram steering system that connects the pitman arm and idler arm. Also called a "relay rod."
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| Center Of Gravity |
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An imaginary point around which the weight of a vehicle is centered. A lower center of gravity improves handing stability and cornering agility. The center of gravity can be lowered by installing shorter suspension springs and/or low profile tires.
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| Centerline |
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The geometric center of the suspension defined by a line that runs the length of the vehicle and bisects the midpoints of the front and rear axles. Used as a reference line in alignment for measuring toe and thrust angle.
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| Ceramic Filter |
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A filter composed of porous ceramic.
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| Cetane Rating |
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A rating for diesel oil that indicates how easily the fuel ignites and how fast it will burn. The rating is obtained by measuring the time lapse between fuel injection and ignition.
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| CFC Certification |
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A process whereby technicians take an EPA approved course on R-12 recovery and recycling, and pass a written examination. CFC certification is required to work on all A/C systems, but no additional certification is required for servicing R-134a systems.
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| Change Of State |
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The rearrangement of the molecular structure of matter as it changes from one physical state to another (solid, liquid or gas). Also called a "phase" change.
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| Charcoal Canister |
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A storage device in the evaporative emissions control system. It is a small cylindrical or rectangular container that contains activated charcoal particles. The charcoal traps gasoline vapors from the fuel tank (and carburetor on older vehicles). Later, t
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| Charge |
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A specific amount of refrigerant or compressor oil by weight. The vehicle manufacturer for individual A/C system applications specifies this.
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| Charging System |
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The charging system includes the alternator, voltage regulator which is often a part of the alternator itself), the battery, and the indicator gauge or warning light on the dash (See Alternator, Battery and Voltage Regulator). The charging system's job is
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| Chassis |
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The frame of a car including the engine, front and rear axles, springs, steering system and gas tank.
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| Check Engine Light |
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A warning light that comes on if the computerized engine control system detects an engine performance or emissions problem. Also called the "Malfunction Indicator Lamp" (MIL). To determine the nature of the problem, the computer system must be accessed to
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| Check Valve |
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Any one-way valve installed to permit the flow of air, fuel or vacuum in one direction only.
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| Chlorofluorocarbons (CFCs) |
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A family of manmade chemicals containing chlorine that include R12 automotive air conditioning refrigerant. CFCs have been blamed for a deterioration of the Earth's protective ozone layer. CFCs have been phased out of production by international agreement
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| Choke |
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device, usually a moveable valve, placed in the path of a carburetor to restrict the flow of air.
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| Circuit Breaker |
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A switch that protects an electrical circuit from overload by opening the circuit when the current flow exceeds a predetermined level. Some circuit breakers must be reset manually, while most reset automatically.
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| Classic Car |
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A car that is considered among the finest of its kind, generally makes and models produced from 1925-1948.
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| Classic Car Club of America |
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Organization of classic car enthusiasts. Address is P.O. Box 443, Madison, NJ 07940.
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| Clear Coat |
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Clear coat paint refers to the clear (non-pigmented) top coat paint that is applied over a colored base coat paint, and is found on most vehicles built in recent years. Clear coat paint increases the vehicle's paint durability, gloss and resistance to har
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| Closed PCV System |
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Widely used design in which the positive crankcase ventilation (PCV) system takes fresh air from the clean side of the air cleaner, passes it through the crankcase, and delivers it to the base of the carburetor or to the intake manifold.
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| Closed Loop |
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The basic principle of electronic engine management in which input from an oxygen sensor allows the engine control computer to determine and maintain a nearly perfect air-fuel ratio. To enter closed loop operation, the oxygen sensor must be producing a vo
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| Clutch |
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An apparatus that disconnects the engine from the transmission in order for the car to change gears and then enables the gears to resume contact and turn together at a new speed.
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| Clutch Pedal |
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The pedal to the left of the brake pedal on cars with manual transmissions that enables the driver to change gears.
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| CMA |
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Chemical Manufacturers Association. Trade organization for chemical manufacturers establishing testing protocol, known as the CMA Code, for motor oils.
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| Coil (Ignition) |
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A transformer in the ignition circuit that steps up the voltage provided to the spark plugs.
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| Coil-On-Plug Ignition (COP) |
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A type of Distributorless ignition system where individual ignition coils are mounted directly over each spark plug. No spark plug wires are used.
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| Coil Springs |
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A type of spring made of wound heavy-gauge steel wire used to support the weight of the vehicle. The spring may be located between the control arm and chassis, the axle and chassis, or around a MacPherson strut. Coil springs may be conical or spiral wound
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| Compliance |
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The "give" or flexing that occurs in the suspension and steering due to the compression of rubber bushings and joint play. A small amount of compliance is desirable because it absorbs shocks and dampens vibrations to reduce steering feedback and harshness
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| Compressor |
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The refrigeration system component that pumps refrigerant and increases the pressure and temperature of refrigerant vapor. The compressor is belt driven via a magnetic clutch, and may be a piston or scroll type design. A compressor failure can throw metal
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| Compressor Oil |
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The oil within the A/C system that lubricates the compressor. R12 systems use a special type of mineral oil. R134a systems use either a PAG or ester-based oil. A certain amount of compressor oil must be in the system at all times to prevent compressor dam
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| Condensation |
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The process whereby a vapor changes to a liquid. This requires a "cooling effect" to draw heat away from the vapor. When the temperature of the vapor reaches a certain point, droplets of liquid (condensate) begin to form. Condensation of the refrigerant v
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| Condenser |
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1 - An electrical device that acts to store an electrical charge preventing voltage surges. 2 - A radiator-like device in the air-conditioning system in which refrigerant gas condenses into a liquid, giving off heat.
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| Conduction |
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The transmission of energy (heat) through a medium without perceptible motion of that medium (direct contact).
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| Conductor |
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Any material through which an electrical current can be transmitted easily.
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| Constant Velocity (CV) Joint |
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A Constant Velocity Joint is one that provides consistent drive shaft speeds regardless of the operating angle of the joint. CV joints are used primarily in on the drive shafts of front-wheel drive vehicles, and they come in two basic varieties: the Rzepp
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| Contact Patch |
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The area of the tire's tread that is in actual contact with the ground. (See Footprint) Harmonic marking Markings on wheels and tires that allow match mounting to cancel tire and wheel runout, minimizing vibration.
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| Continuity |
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Continuous or complete circuit. Can be checked with an ohmmeter.
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| Convection |
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Suspension components that connect the steering knuckles to the chassis or sub-frame, and allow the knuckles to move up and down.
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| Coolant |
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A mixture of water and antifreeze (ethylene glycol) which lowers the freezing point of the water in the cooling system, prevents rust and corrosion, lubricates the water pump, and picks up heat from the engine, transferring it to the air passing through t
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| Coolant Temperature Sensor |
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A variable resistance thermistor that changes resistance as the engine's coolant temperature changes. The sensor's output is monitored by the engine computer to regulate various ignition, fuel and emission control functions, and to turn the radiator-cooli
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| Cooling System |
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A system utilizing either air or water to remove heat from the engine.
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| CORE Charge |
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An acronym for "Cash On Return". Rebuildable parts that can usually be redeemed for a portion of their original purchase price. CORE charges are usually collected for engines, crankshafts, alternators, radiators and brake shoes.
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| Cornering Force |
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The lateral frictional force generated by a cornering tire, acting in opposition to the centrifugal force.
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| Cost |
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The price that the shop or dealership pays for a part compared with the marked-up price charged to consumers.
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| Countershaft |
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An intermediate shaft that is rotated by a mainshaft and transmits, in turn, that rotation to a working part.
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| Cradle |
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A structural member used in many front-wheel drive cars that supports the engine and transaxle. The cradle is bolted to the subframe, and is also connected to the lower control arms. The position of the cradle is important because it affects camber and ca
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| Creeper |
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A small, four-wheeled platform that allows a mechanic to move underneath a car in order to perform checkups and repairs.
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| Cross Caster |
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The difference side-to-side between caster settings. More than half a degree difference may cause a steering pull toward the side the least (negative) caster. Caster on the left front wheel is sometimes decreased to compensate for high road crown.
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| Cross Member |
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A structural component that bolts between the frame rails or attaches to the sub-frame of a unibody. The lower control arms may be attached to the cross member. The position of the cross member is important because it affects camber, caster and setback.
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| Crankcase |
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The lower pad of an engine in which the crankshaft and related parts operate.
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| Crankcase Emissions |
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See blowby.
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| Crankshaft |
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The main driving shaft of an engine that receives reciprocating motion from the pistons and converts it to rotary motion.
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| Cross-Drilled Disc |
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Disc with friction surfaces which have been drilled with rows of holes to improve cooling, reduce weight and provide an escape route for dirt and gasses which can be wedged between the pads and disc. High-performance rotors can be both cross-drilled and s
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| Crown |
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The center area of a tire's tread.
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| Crude Oil |
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unrefined petroleum in its natural form when taken from the ground. Crude oil is the basis for gasoline, engine oil, diesel oil, kerosene and other petroleum-based products.
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| Curved Vane Disc |
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Ventilated rotor in which the cooling channels (or vanes) have been curved to increase their ability to pump out hot air and cool the disc. Curved vane rotors are more efficient than conventional ventilated rotors and, as a side benefit, tend to be strong
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| Cycling Clutch Orifice Tube (CCOT) |
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A refrigerant system in which a fixed displacement compressor is engaged and disengaged to maintain the refrigeration cycle. By cycling the compressor clutch on and off, the cooling output of the system is regulated.
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| Cylinder Block |
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The main structural member of an engine in which is found the cylinders, crankshaft and other principal parts.
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| Cylinder Head |
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The detachable portion of the engine, usually fastened to the top of the cylinder block and containing all or most of the combustion chambers. On overhead valve engines, it contains the valves and their operating parts. On overhead cam engines, it contain
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| Cylinder |
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In an engine, the round hole in the engine block in which the piston(s) ride.
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| Cross Camber |
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The difference side-to-side between camber settings. More than half a degree difference may cause a steering pull toward the side with the most (positive) camber.
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| Control Arms |
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Suspension components that connect the steering knuckles to the chassis or sub-frame, and allow the knuckles to move up and down.
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| Circuit |
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Any unbroken path through which an electrical current can flow. Also used to describe fuel flow in some engines.
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| Centrifugal Advance |
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A mechanical method of advancing the spark timing by using flyweights in the distributor that react to centrifugal force generated by the distributor shaft rotation.
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