Chevrolet Trax: Automotive terminology & definitions

ABRASIVE CLEANING

removing contaminants using a cleaning agent containing abrasive material. Cleaning that requires physical abrasion (e.g., glass bead blasting, wire brushing).

ADDITIVE

in automotive terminology, a substance added to a liquid, such as engine oil, transmission fluid, gear oil or coolant to enhance its properties.

AEROSOL

a cloud consisting of particles dispersed in a gas or gases

AFTERMARKET

broad term that applies to any change after the original purchase, such as adding equipment. When applied to AFVs, it refers to conversion devices or kits for conventional fuel vehicles.

ALIGNMENT

an adjustment to bring parts or components into a line or proper coordination.

ALTERNATOR

a belt driven device that provides electrical current for the vehicle's charging system.

ANTIFREEZE

a material such as ethylene glycol which is added to water to lower its freezing point; used in an automobile's cooling system.

AQUAPLANING

the loss of traction that results when a tire loses sufficient grip on a wet roadway, the tire actually loses contact with the road surface and rides on a thin film of water.

AUTOMATIC TRANSMISSION FLUID (ATF)

the oil that is used in an automatic transmission.

BATTERY ACID

the sulfuric acid solution used as the electrolyte in a battery.

BATTERY CELL

the part of a battery made from two dissimilar metals and an acid solution. A cell stores chemical energy to be used later as electrical energy.

BATTERY SAVER

the battery saver system is an effective way to prevent complete battery discharge when the engine is shut down. Based on the preset time-limit, the system automatically disconnects the battery load when the battery is not being charged. Depressing the reset push button will enable the battery to be reconnected for additional periods of time. Critical systems can be set up to have battery power maintained.

BATTERY

batteries are the principal energy storage devices for hybrid electric vehicles (HEVs). Desirable attributes of high-power batteries for HEV applications are high-peak and pulse- specific power, high specific energy at pulse power, a high charge acceptance to maximize regenerative braking utilization, and long calendar and cycle life. Developing methods/designs to balance the packs electrically and thermally, developing accurate techniques to determine a battery's state of charge, and developing abuse-tolerant batteries, and recyclability are additional technical challenges.

BEARING RACE

the machined surface of a bearing assembly against which the needles, balls or rollers ride. The outer race is also called a cup.

BEARING

part that supports and reduces friction between a stationary and moving part or two moving parts.

BLEEDER VALVE

a valve located on disc brake calipers, wheel cylinders and some master cylinders that allows air and fluid to be removed from the brake system.

BOILING POINT

the temperature at which a liquid turns to vapor.

BRAKE DRAG

a condition that occurs when brake pads or shoes are in continuous contact with the disc brake rotors or brake drums.

BRAKE FLUSHING

a procedure to clean the brake hydraulic system with fresh, clean fluid that should be performed whenever new parts are installed, if there is any doubt as to the grade of fluid in the system, if a glycol fluid has been mixed with a silicone-based fluid, or if the fluid has been contaminated with petroleum or mineral based fluids.

BRAKE HOSE

flexible hoses that connect the brake lines on the chassis with the calipers or wheel cylinders, or the junction block on a solid axle.

BRAKE LINE

metal tubing that carries the brake fluid from the master cylinder to other brake system components.

CHARGE

the electrical current that passes through the battery to restore it to full power; to fill, or bring up to the specific level, an A/C system with refrigerant; the required amount of refrigerant for an A/C system.

CHARGING SYSTEM

the system that supplies electrical power for vehicle operation and recharges the battery.

CHEMICAL CLEANING

relies primarily on chemical action to remove dirt, grease, scale, paint or rust.

COLD CRANKING AMPS

the amount of cranking amperes that a battery can deliver in 30 seconds at OºF ( - 18ºC).

COLD START

difficulty of starting an internal combustion engine in cold weather because of gasoline, which evaporates more slowly when it is cold; oil, which gets thicker in cold weather; and the chemical reactions inside the battery, which progress more slowly in cold weather.

CONDENSER

a device, similar to a radiator, in which the refrigerant loses heat and changes state from a high-pressure gas to a high pressure liquid as it dissipates heat to the surrounding air.

COOLANT

the mixture of water and antifreeze used in an engine's cooling system to maintain the engine's temperature throughout Its operating range.

COOLING FAN

a mechanically or electrically driven propeller that draws air through the radiator.

COOLING SYSTEM

the system used to remove excess heat from an engine and transfer it to the atmosphere. Includes the radiator, cooling fan, hoses, water pump, thermostat and engine coolant passages.

CORE PLUGS

plugs that fill holes in a block or head left from the casting process. Also called freeze, welsh or expansion plugs.

CORE

in automotive terminology, the main part of a heat exchanger, such as a radiator, evaporator or heater.

Usually made of tubes, surrounded by cooling fins, used to transfer heat from the coolant to the air.

CORROSION INHIBITORS

additives used to inhibit corrosion (e.g., rust) in the fuel system.

CROSSFLOW RADIATOR

a radiator in which coolant enters on one side, travels through tubes, and collects on the opposite side (see downflow radiator).

DIFFERENTIAL

gear assembly that transmits power from the driveshaft to the wheels; allows the outside wheel to turn faster than the inside when cornering.

DIGITAL VOLT/OHMMETER (DVOM)

an instrument that measures volts, ohms and amps and displays the results numerically.

DIRECTIONAL TIRE

tire with a tread pattern that is designed to give maximum traction by removing water from under the tread in such a way as to minimize the risk of aquaplaning. Directional tires must be installed to turn in a specific direction.

DOWNFLOW RADIATOR

a radiator in which coolant enters the top of the radiator and is drawn downward by gravity (see crossflow radiator).

DRIVETRAIN

all of the components that generate power and transfer it to the vehicle's wheels.

DUAL MASTER CYLINDER

a master cylinder that has one cylinder bore, but two pistons and two fluid reservoirs. Each piston applies hydraulic pressure to two wheels only. In the event one of the hydraulic circuits fails, the other provides enough braking power to stop the vehicle.

DUO-SERVO DRUM BRAKES

a drum brake design that provides increased stopping power due to the servo or self- energizing action of the brake shoes.

EGR VALVE

see 'exhaust gas recirculation (EGR) valve',

ELECTROLYTE

a material whose atoms become ionized (electrically charged) in solution. In automobiles, the battery electrolyte is a mixture of sulfuric acid and water.

ELECTRONIC AIR SUSPENSION

electronic air suspension provides the comfort of riding on air with adjustable spring rates and capability to change ride height and load-carrying ability. Under normal driving conditions, an electronic air suspension vehicle rides at the same height as a traditionally sprung vehicle. With a heavy load, ride height is increased automatically. On current vehicles, the suspension lowers the ride height by 20 mm at highway speeds for improved aerodynamics, with about 2 percent better fuel economy. Lower ride height also can improve on-center feel of steering due to the change in suspension geometry and increased caster angle.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

a sensor which works by a negative coefficient thermistor that loses resistance as its temperature goes up (just like the intake air temperature sensor). When the computer applies its 5-volt reference signal to the sensor, this voltage is reduced through a ground circuit by an amount corresponding to the temperature of the engine coolant

EVAPORATOR

a heat exchanger, in which low-pressure refrigerant flows and changes state, absorbing heat from the surrounding air.

EXHAUST GAS RECIRCULATION (EGR)

component in the EGR system, used to meter a controlled amount of exhaust gas into the intake air stream.

EXHAUST GAS RECIRCULATION (EGR) VALVE

an emissions control technique that reuses engine exhaust gases as part of the intake air supply to help reduce harmful emissions (especially Nox).

FAHRENHEIT

a scale of temperature measurement with the boiling point of water at 212ºF. In the metric system, water's boiling point is 100ºCelsius.

FAN CLUTCH

a device attached to a mechanically driven cooling fan that allows the fan to freewheel when the engine is cold or the vehicle is driven at speed.

FAN SHROUD

an enclosure that routes air through the radiator cooling fins.

FAN

a mechanically or electrically driven propeller that draws or pushes air through the radiator, condenser, heater core or evaporator core.

FILTER

a screen or filter element that can be made to filter specified sizes of particles from air or liquid.

FLOODING

a condition in which unvaporized fuel in the intake manifold and/or combustion area, prevents the engine from starting.

FOOT POUND

a unit of measurement for torque. One foot pound is the torque obtained by a force of one pound applied to a wrench handle that is 12-in. long; a unit of energy required to raise a weight of one pound, a distance of one foot.

FOUR STROKE CYCLE ENGINE

an engine, either gasoline or diesel that uses four strokes: intake, compression, power and exhaust. A firing impulse occurs every two turns of the crankshaft. When this engine is a gasoline engine it is also called an Otto cycle engine after its inventor. A diesel engine is called a Diesel cycle engine for the same reason.

FREEZE PLUG

another name for core plug.

FRONT WHEEL DRIVE

the entire drivetrain is located at the front of and drives the front wheels of the vehicle.

FUSE

a metal circuit protection device that melts when there is a circuit overload or short.

FUSIBLE LINK

a smaller gauge wire that is included in an electrical circuit to provide circuit protection. The smaller gauge wire will melt when the circuit is overloaded.

GASKET

a material such as artificial rubber, cork, or steel used to seal between parts that would otherwise leak fuel, coolant, lubricants or combustion gases.

GENERATOR

a device that converts mechanical energy into electrical energy; SAE J1930 nomenclature for an alternator; a generating device that uses diode rectifiers to convert ac to dc.

HALFSHAFT

transfers power from the transaxle to the front wheels on a front-wheel drive vehicle. Also used on some vehicles with rear-wheel drive and independent rear suspension to transfer power from the differential to the rear wheels. Consists of a stub shaft that is splined into the differential side gear, another stub shaft that is splined into the wheel hub, an interconnecting shaft, and two CV-joints, which connect the interconnecting shaft to the stub shafts.

HEATER CORE

a radiator-like device used to heat the inside of a vehicle. Hot coolant is pumped through it by the water pump, and heat from the coolant moves from the heater core to the passenger compartment as the blower fan forces air through it.

HUB

mounting point for the wheelan an axle or spindle; the part of the synchronizer assembly that is splined to the transmission shaft; the center part of a wheel, gear, etc., that rides on a shaft.

HYDRAULIC PRESSURE

pressure exerted through a liquid.

HYDROMETER

an instrument used to measure the specific gravity of a solution.

IMPEDANCE

the total resistance of an electrical device measured in ohms.

INCH POUND

one twelfth of a foot pound.

INDEPENDENT SUSPENSION

a suspension in which each wheel can travel up and down without directly affecting the position of the opposite wheel.

INNER BEARING RACE

inner part of a ball or roller bearing that provides a surface for the balls or rollers to rotate.

INTEGRATED CIRCUIT

an electrical circuit containing many interconnected amplifying devices and circuit elements formed on a single body or chip of semiconductor material; diodes, transistors and other electronic components mounted on semiconductor material and able to perform numerous functions.

INTERCOOLER

a component on some turbocharged engines used to cool the compressed intake air.

INTERNAL COMBUSTION ENGINE (ICE)

engine that converts the energy contained in the fuel inside the engine into motion. Combustion engines use the pressure created by the expansion of the gases to do mechanical work.

JAM NUT

a locknut.

KEEP-ALIVE MEMORY

a series of vehicle battery-powered memory locations in the microcomputer that store information on input failure, identified in normal operations for use in diagnostic routines; adapts some calibration parameters to compensate for changes in the vehicle system.

LEAF SPRING

a suspension spring consisting of a single flat plate made of steel or composite material or several steel plates bundled together.

LIGHT-DUTY VEHICLE

passenger cars and trucks with a gross vehicle weight rating of 8,500 or less.

LIMITED SLIP DIFFERENTIAL

a type of differential that uses clutches to supply a major portion of the drive torque to the wheel that has better traction when one wheel is slipping,

LITER (L)

a metric measurement used to calculate the volume displacement of an engine. One liter is equal to 1,000 cubic centimeters or 61 cubic inches.

LUBRICATION

the process of introducing a friction reducing substance between moving parts to reduce wear.

MACPHERSON STRUT

the principal device in the suspension of the same name, in which the spring, shock absorber and sometimes the steering knuckle are combined in a single unit.

MALFUNCTION INDICATOR LIGHT (MIL)

also known as the CHECK ENGINE or SERVICE ENGINE SOON light on many vehicles. The MIL comes on when the ignition is first turned on (to check the bulb) and then goes out once the engine is started, unless a trouble code is stored in the computer. If the MIL is on when the vehicle is running, there has been a malfunction on one of the sensor or actuator circuits monitored by the computer, and a diagnosis will have to be made by retrieving the code.

MASTER CYLINDER

the primary fluid pressurizing device in some hydraulic systems. In automotive use, it is found in the brake and hydraulic clutch systems and is pedal-activated, either directly or through a vacuum assist unit.

MILLIMETER

the base of metric size measurement. One millimeter equals 0.039370-in. One inch is equal to 25.4 m m.

MULTIVISCOSITY OIL

chemically-modified oil that has been tested for viscosity at cold and hot temperatures.

OFF-ROAD

any non-stationary device, powered by an internal combustion engine or motor, used primarily off the highways to propel, move, or draw persons or property, and used in any of the following applications: marine vessels, construction/farm equipment, locomotives, utility and lawn and garden equipment, offroad motorcycles, and off-highway vehicles.

OHM

a unit of electrical resistance of a circuit in which an electromotive force of one volt maintains a current of one ampere, named after German physicist Georg Ohm.

OHMMETER

an instrument that measures electrical resistance in ohms.

OHM'S LAW

a basic law of electricity expressing the relationship between current, resistance and voltage in any electrical circuit. Ohm's law states that the voltage in a circuit is equal to the current multiplied by the resistance.

OIL COOLER

device used to remove heat from the engine or transmission oil. There are oil-to-air coolers and oil coolers that are incorporated into the vehicle's cooling system.

OIL PAN

the part that encloses the crankcase at the lower end of the block.

OIL PRESSURE

the pressure that results from resistance to flow from the oil pump. As the pump turns faster, it produces more flow. A relief valve limits the amount of pressure it can produce.

ON-CAR BALANCING

the practice of spinning a wheel on the car to balance the wheel and all other rotational components together.

ORIGINAL EQUIPMENT MANUFACTURER (OEM)

the original manufacturer of a vehicle or engine.

OSCILLOSCOPE

an instrument that displays electrical activity in the form of line patterns on a screen.

OUTER BEARING RACE

outer part of a bailor roller bearing that provides a surface for the balls or rollers to rotate. Can be integral with the bearing or a separate part.

OXIDATION

the process of combining with oxygen, resulting in rusting or burning. Rust is slow oxidation; fire is rapid oxidation.

PAG

polyalkyline glycol oil (lubricant) used with A/C systems containing R- 134a refrigerant.

PARALLEL CIRCUIT

a circuit with more than one path for the current to follow.

PARKING BRAKE

a system that applies the brakes mechanically through a series of linkages and cables. Depending on the vehicle, the parking brake system will either be actuated using a foot pedal or a hand-operated lever.

PASCAL'S LAW

the law of physics stating that liquids are noncompressible, and that a force applied to the top of a liquid in a closed container is exerted equally in all directions.

PCV SYSTEM

see 'positive crankcase ventilation system'.

PCV VALVE

a part of the positive crankcase ventilation system. Meters crankcase vapors into the intake manifold.

PLAY

the relative movement between or among parts.

POLARITY

the condition of being positive or negative relative to a reference point or object; the particular state (positive or negative) with reference to the two magnetic poles.

POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM

a system that controls crankcase emissions by using a valve to meter crankcase vapors nto the intake manifold.

POWER BRAKES

a system that uses vacuum or hydraulic pressure to assist the driver with brake application.

PSI

measurement of pressure in pounds per square inch.

RADIAL RUNOUT

the out-of-roundness ot a wheel or tire.

RADIATOR CAP

a device that seals the radiator and maintains a set pressure in the cooling system.

RADIATOR

the part of the cooling system that acts as a heat exchanger, transferring heat to atmosphere. It consists of a core and holding tanks connected to the cooling system by hoses.

REAR WHEEL DRIVE

system where the driveline drives the rear wheels of the vehicle. Most often the engine is located in the front of the vehicle and a transmission and drive shaff connect to a drive axle, however there are also systems where the entire drive line is located toward the rear of the vehicle.

REAR WHEEL STEERING

a system used on a some vehicles to change the toe of the rear wheels to either steepen a sharp turn or enhance cornering on a shallower, faster one.

RESISTOR

an electrical device installed in a circuit to lower voltage and current flow.

RIDE HEIGHT

the dimension between a fixed point on the vehicle and the pavement. The fixed point varies according to vehicle and manufacturer. Also called vehicle height.

RUNOUT

wobble or deflection beyond a rotating part's normal plane of movement.

SCAN TOOL

microprocessor designed to communicate with a vehicle's on-board computer system to perform diagnostic and troubleshooting functions.

SEMICONDUCTOR

a material that is neither a good conductor of electricity nor a good insulator.

SENDING UNIT

a mechanical, electrical, hydraulic or electromechanical device which transmits information to a gauge or other receiving unit.

SERIES CIRCUIT

a circuit that has only one path for current to follow.

SERIES-PARALLEL CIRCUIT

a circuit that combines series and parallel circuits.

SERVO

a device, such as an electric motor or hydraulic piston, that is controlled by an amplified signal from a low power command device.

SHOCK ABSORBER

a device used to dampen the oscillation of the suspension caused by irregularities in the road surface.

SHORT CIRCUIT

a condition that occurs in an electrical circuit when the current bypasses the intended load and takes a path with little or no resistance, such as another circuit or ground.

SPECIFIC GRAVITY

the ratio of the weight or mass of the given volume of a substance to that of an equal volume of another substance, e.g. - water for liquids and solids; air or hydrogen for gases, are used as standards.

SPONGINESS

the feel of a soft or mushy brake pedal usually caused by trapped air in the hydraulic system.

SPRUNG WEIGHT

the weight of all the vehicle components that are supported by the springs; see 'unsprung weight'.

STABILIZER BAR

a torsion-bar spring connecting the suspension on either side of the vehicle. When a vehicle rolls to the side in a turn, the suspension at the outside wheel compresses and the suspension at the inside wheel extends. The stabilizer bar that connects them twists to apply a counteracting force to hold the vehicle closer to level. Also called an anti-roll bar or sway bar.

STARTER

the electric motor that is used to start an engine.

STUD

a fastener that has screw threads at both ends.

TECHNICAL SERVICE BULLETIN (TSB)

information published by vehicle manufacturers that describe updated service procedures and service procedures that should be used to handle vehicle defects.

TENSIONER

a device used with a timing chain or belt to maintain its tension.

THERMOSTAT

a device installed in the cooling system that allows the engine to come to operating temperature quickly and then maintain a minimum operating temperature.

TIMING BELT

a toothed reinforced belt used to drive the camshaft from a sprocket on the crankshaft.

TOLERANCE

the difference between the allowable maximum and minimum dimensions of a mechanical part; the basis for determining the accuracy of a fitting.

TORQUE SEQUENCE

a specified order in which a component's mounting bolts should be tightened

TORQUE WRENCH

a breaker bar or ratchet wrench with an indicator that measure the twisting effort applied to a fastener during tightening.

TORQUE

twisting effort on a shaft or bolt.

TWIN I-BEAM SUSPENSION

a type of independent front suspension and used on light trucks and vans. It consists of two I-beams supported by coil springs, and the steering knuckles/spindles, which are connected by king pins or ball joints. The inner end of the axle connects to the vehicle frame through a rubber bushing. A radius arm also connects to the frame through rubber bushings to control wheelbase and caster.

UNIVERSAL JOINT (U-JOINT)

a joint that allows the drives haft to transmit torque at different angles as the suspension moves up and down.

UNSPRUNG WEIGHT

the components of a vehicle that rest directly on the road surface without being supported by the suspension springs.

VACUUM

a pressure lower than atmospheric.

VOLT

unit of electromotive force. One volt of electromotive force applied steadily to a conductor of one-ohm resistance produces a current of one ampere.

VOLTAGE DROP

voltage lost by the passage of electrical current through resistance.

VOLTMETER

an instrument used to measure voltage in a circuit.

WATER PUMP

a device used to circulate coolant through the engine.

WHEEL ALIGNMENT

the adjustment of suspension and steering components to optimize steering control and minimize tire wear.

WHEEL BALANCE

the condition in which a wheel/tire assembly has equal weight around its center, preventing vibration at high speeds. Wheel balance can be static, such as on a bubble balancer, or dynamic, such as with a spin balancer.

WHEEL WEIGHTS

small weights, usually made of lead, attached either mechanically or by adhesive to a wheel/tire assembly to correct its balance.

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