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Safety Rim
Wheel designed with small ridges that hold a tire in place if a blowout or flat occurs.
Safety Washer
On a non-driving wheel, flat washer that keeps wheel bearing from rubbing on spindle adjusting nut.
Satellite Face
Valve face coated with hard metal to withstand high temperatures.
Saving Memory
A method of preventing loss of information in computer memory by connecting a small voltage source to it before disconnecting the vehicle's battery cables.
Scanner
Electronic system used to analyze engine and computer operations.
Schrader
Valve
A spring-loaded valve, similar to a tire valve, used in air conditioning systems.
Screw Extractor
Tool threaded opposite normal direction, so it can be used to unscrew a broken bolt or screw.
Seal
A formed material or paste-like substance used to prevent leaks.
Seal Alignment Tool
Device used to center seal around the crankshaft snout when mounting some engine front covers.
Sealant
A material applied, in liquid or paste form, to prevent leakage between parts.
Sealing Rings
Rings placed around either end of a turbo shaft to keep oil from leaking into the turbocharger housing.
Seal Part Number
Code number stamped on a seal that is used when ordering a replacement.
Seat Width
The area of the valve seat that is actually in contact with the valve face.
Secondary
In a carburetor, the components that operate under high engine output conditions.
Secondary Circuit
In an ignition system, all components operating on coil (high) voltage.
Secondary Pattern
Pattern of high-voltage (ignition secondary) changes, as shown on an oscilloscope.
Secondary Wire
Wire used in a vehicle ignition system. It carries high voltage from coil to spark plugs.
Secondary Wire Resistance
A type of test performed to check condition of a spark plug wire or coil wire.
Sector Shaft
Output gear in a re-circulating ball gearbox.
Select Fit Parts
Parts that have been selected and installed to improve fit or clearance.
Self-Diagnosis
The ability of a computer system to check circuits and output a code showing the nature or location of the problem.
Self-Sealing Tire
One with a scaling compound applied to its liner to stop air leakage in case of puncture.
Semi-Centrifugal Clutch
One that uses weighted release levers or rollers on the pressure plate, and the effects of centrifugal force, to increase clamping pressure on the clutch disk.
Semiconductor
Substance that acts as an insulator or a conductor, depending upon conditions.
Semi-Floating Axle
Most common type of rear axle for automobiles.
Sensor
Device that monitors and reports a condition (such as engine temperature) to the vehicle computer.
Sensor Rotor
A toothed wheel that operates at the same rpm as the vehicle wheel.
Separator
An insulating material placed between plates of a battery.
Service Manager
Person responsible for the complete service and repair operation.
Service Manual
Book with detailed information on specific car repairs. Also called a shop manual.
Service Publications
In addition to service manuals, there are other publications (such as owner's manuals and technical bulletins) that provide information on vehicle servicing.
Service Valves
Points at which pressures in an air conditioning system can be checked, and refrigerant removed or replaced.
Servo
Piston that operates a band in an automatic transmission.
Servo Action
Situation in which primary shoe of a drum brake system helps apply the secondary shoe.
Servo Motor
One that can be stopped in exact positions (degrees of rotation).
Servo Motor Actuator
A small DC motor that can turn or move parts.
Set Screw
Headless fastener used to secure a part on-to a shank.
Shaft Run-Out
Wear or damage (bending) causing a shank to not run true around its axis.
Sharp Valve Margin
A result of excessive grinding of valve face, leaving no margin.
Shell
A component of an automatic transmission clutch that connects the front clutch drum and the sun gear of a planetary gear set.
Shift Fork
Device that physically moves synchronizer and gear together as a result of shift lever (gearshift) movement.
Shift Lever
The handle operated by the vehicle driver to manually shift from gear to gear.
Shift Linkage Adjustment
Making sure transmission linkage positions match the gear selector positions.
Shift Linkage Alignment Pin
Tool used to properly align shift linkage rods for proper operation.
Shift Rail
A manual transmission linkage that is contained within the transmission case.
Shock Absorber
Device that uses air or hydraulic pressure to dampen up-and-down motion of vehicle.
Shock Actuators
Solenoid-operated valves that control fluid flow inside shock absorbers in an electronic shock absorber system.
Shock Bounce Test
Method of quickly checking whether shock absorbers need replacement.
Shock Compression and Extension
Actions of shock absorbers resulting from the vehicle traveling over road bumps.
Shock Mode Switch
Dash switch that allows driver to select desired ride stiffness in an electronic shock
absorber system.
Shop Supervisor
A person in charge of a group of technicians in a large garage.
Short Block
The bottom end of the engine, including the cylinders, pistons, and crankshaft.
Short Circuit
Excess current flow that occurs when a conductor touches ground.
Shorted Condenser
One with a direct electrical connection to ground.
Shorted Injector Coil
A short-circuited solenoid coil is preventing injector operation.
Shroud
Enclosure around a fan, used to direct airflow through the radiator.
Sidewall
Portion of tire between tread and bead.
Simple Circuit
One consisting of a power source, a load, and conductors.
Single-Point
Injection system with fuel sprayed from a single location into the intake manifold.
Sintered Bronze Filter
A porous metal fuel filter.
Six-Point
Box end wrench with six indentations, or gripping teeth.
Slant Engine
One with a single bank of cylinders tilted to one side.
Slave Cylinder
Hydraulic cylinder that produces the movement of the clutch fork.
Slide Hammer Puller
Tool used to break loose and remove an axle that is stuck in its housing.
Slipper Skirt
Material remaining after part of piston below pin is removed for better crankshaft clearance.
Slip Rings
Components mounted on the rotor shaft of a generator to provide current to rotor windings.
Slip Yoke
Component that connects transmission to the front universal joint of the driveline.
Slow Charger
One that feeds a small current into the battery over a long period of time.
Smog
The cloud of airborne pollutants visible over major population centers.
Smoke Meter
Device for testing the amount of smoke (ash or soot) in diesel exhaust.
Smooth DC
Direct current without "ripples" or "spikes" due to fluctuating voltages.
Snap Ring
Spring steel ring that snaps into a groove to act as a retainer on a shaft.
Sodium Filled Valve
Hollow construction accepts sodium filling for more even cooling.
Soft Failure
One that is intermittent, such as the make/break connection from a loose terminal.
SOHC
Single overhead cam engine.
Soldering Gun
Tool that applies heat to joined wires so that solder can be melted into the joint.
Solenoid Actuator
One with a moving metal core that is actuated by an induced magnetic field.
Solvent Tank
Container holding a cleaning solution used for removing grease and other dirt from a part.
Sonar Sensor
Sound wave sensor used to detect road conditions in some electronic shock absorber systems.
Spark Ignition
System that uses an electric arc to ignite fuel.
Spark Knock
Noise caused by spark plug firing too early.
Spark Line
Oscilloscope line showing voltage needed to maintain an arc across the spark plug gap.
Spark Plug
Devices that emit an electrical arc at the tip to ignite the air-fuel mixture in an engine cylinder.
Spark Plug Gap
See Plug gap.
Spark Test
Check of the spark intensity (brightness and length of arc).
Spark Tester
Device used to cheek operation of ignition system.
Specialized Manual
Service manual devoted to a specific vehicle area, such as engines or braking systems.
Specialized Mechanic
A technician who is an expert on one system of a car.
Special Tools
Fixtures or tools needed for certain repairs or adjustments. They are described in service manuals.
Specific Gravity
Weight or density of a liquid.
Speed Control System
Method of regulating a car's throttle to maintain a preset speed. Also called cruise control.
Spider Gears
Idler and axle gears in the differential that drive the rear axles of a vehicle.
Spindle
Stationary shaft used to support rotating wheel assembly on non-driving wheels.
Spindle Adjusting Nut
A nut threaded on end of wheel spindle to adjust wheel bearing.
Spin On Oil Filter
One that is replaced as a unit.
Splash Oiling
Oil distributed to needed areas by spraying or splashing.
Splines
A series of slots cut into a shaft and mating part.
Spongy Brakes
Braking system that is "soft" feeling, usually as a result of air trapped in the hydraulic system.
Spring Bind
Situation that can occur when a valve spring is fully compressed and locks the valve train.
Spring Fatigue
Weakening of springs that allows the height of the car (and thus road clearance) to decrease.
Spring Free Length
The length of a spring when removed from the engine.
Spring Rate
The stiffness or tension; amount of weight needed to compress or bend a spring.
Spring Tension
The stiffness of a valve spring.
Sprocket Timing Marks
Lines, circles, or dots on crankshaft and camshaft sprockets, aligned to set engine timing.
Spur Gears
Those with teeth cut parallel to the centerline of the drive shaft.
Squish Area
Part of a wedge-shaped combustion chamber.
Staking
Making a small dent in cylinder head metal next to a valve seat to hold it in place after replacement.
Stall
Work area of a repair shop.
Stalling
Condition in which the engine merely stops running.
Stall Speed
Highest speed of impeller rotation in a torque converter without rotation of the turbine.
Stall Test
Method used to shop-test for transmission slippage.
Starter Current Draw Test
Starting test that establishes the number of amps used by the starting system.
Starter Ground Circuit Resistance Test
Check of all parts between the battery negative and the starting motor ground for excess resistance.
Starter Mounted Solenoid
One with a plunger that moves to engage the pinion gear with the flywheel gear.
Starter Relay
Device that uses a small current flow from the ignition switch to control a larger current flow to the starter solenoid.
Starter Shims
Thin metal pieces used to adjust the space between the pinion gear and the flywheel gear.
Starter Solenoid
A high current relay that energizes the starter motor.
Starting Headlight Test
Starting test conducted with headlights turned on to provide a load on the battery.
Starting Motor Rebuild
Process involving disassembly, cleaning, parts replacement, and reassembly of the motor.
Starting System
Electric motor and other components used to rotate the engine until it starts.
Star Wheel
Adjusting screw assembly for drum brakes.
States of Matter
Forms in which a substance can exist (solid, liquid, gas).
Static Imbalance
Lack of balance that causes a wheel to vibrate up and down as it rolls.
Static Pressure Reading
A reading made with the engine off to determine whether a system has an adequate refrigerant charge.
Stator
The stationary magnetic field in a generator. Also component of torque converter
that improves oil circulation and thus, torque.
Stator Support
A stationary tube surrounding the input shaft of a torque converter and supporting the stator.
Stator Test
Ohmmeter check for open or shorted windings in the stator.
Steering Axis Inclination
Angle formed by the inward tilt of ball joints, king pin, or struts.
Steering Column
Assembly consisting of the steering wheel, steering shaft, ignition key mechanism and associated parts.
Steering Gearbox
Gear assembly that turns rotary motion into linear (straight line) left-right motion.
Steering Knuckle
Component that provides support for wheel spindle or bearings surrounding an axle.
Steering Linkage
Components connecting steering gearbox to steering knuckles.
Steering Sensor
Provides wheel orientation and speed data to computer in electronic shock absorber system.
Steering Shaft
Component that transfers turning motion from steering wheel to steering gearbox.
Steering System
The components that let the driver change direction of a vehicle.
Steering Wheel Play
Excessive movement of wheel without causing front wheel movement.
Stem Type Valve
Manual valve that is opened or closed by screwing the valve stem in or out.
Stethoscope
A medical device, also used by auto technicians to better hear internal engine noises.
Stiff Clutch Pedal
A condition caused by binding or other restriction in the clutch mechanism, making the pedal hard to depress.
Stoichiometric Fuel Mixture
A perfect (chemically correct) air-fuel mixture.
Straightedge
A metal ruler or bar, with one edge known to be smooth and straight, used to determine flatness of surfaces.
Strap
Connector between cells of a battery.
Stratified Charge
A combustion chamber design that first ignites the air-fuel mixture in a small chamber connected to the main chamber.
Strut Assembly
Suspension component combining shock absorber, coil spring, and upper damper unit. It replaces the upper control arm.
Strut Cartridge
Replaceable shock absorber unit on a MacPherson strut.
Strut Rod
A rod that fastens to the control arm and frame to keep arm properly oriented.
Stuck Valve
One that will not move up and down freely in the guide; usually, a condition occurring after long storage.
Stumble
See Hesitation.
STY
Suction throttling valve.
Supercharger
Air pump used to push denser fuel-air charge into combustion chambers for increased power.
Superheat Switch
One that shuts down an air conditioning system if refrigerant or oil levels are low.
Superimposed Pattern
Oscilloscope pattern in which the traces for all cylinders are placed one on top of the other.
Surging
Condition in which engine power fluctuates up and down.
Suspension Leveling System
Suspension system designed to keep vehicle level and at proper height even when carrying a heavy load in the truck.
Suspension System
Components that let the wheels move up and down without body movement.
Suspension System Computer
One that accepts sensor input and regulates the stiffness of the vehicle's suspension system.
Sway Bar
A stabilizer that keeps the vehicle body from leaning excessively in turns.
Swing Axle
Axle provided with U-joints to allow for up-and-down suspension movement. Used on vehicles with differential mounted solidly on frame.
Swirl Chamber
Combustion chamber shape that causes the air-fuel mixture to spin as it enters, for better mixing.
Switching Sensor
One that opens or closes a switch in response to a change in condition.
Switch Self Test
Systematic actuation of various switches while using the scanner, providing a check of switch operation.
Synchronizer
Assembly of hub, sleeve, and other components that locks the selected output gear to the output shaft to transmit power. It permits meshing of gears without grinding.
Synthetic Fuels
Liquid fuels made from such solids as coal or tar sand.
System
A group of related parts that perform a specific function.
Systematic Approach
Combining knowledge and a logical process of elimination to solve a problem.
System Bleeding
Removing any trapped air from the entire braking system.
Tach-Dwell:
Combined meter that measures engine rpm and degrees of breaker cam rotation for distributor point adjustment.
Tailpipe
Tubing that carries exhaust from muffler to point at rear or side of the vehicle, where it can be dispersed.
Tank Pickup-Sending Unit
Component that extends into fuel tank to withdraw fuel and send fuel-level information to the fuel gauge.
Tap
Tool for cutting threads inside a hole.
Tappet Clearance
The proper degree of tension (neither too tight nor too loose) for the valve train of an engine.
Taxable hp
General rating of engine size.
TBI
Throttle body (single-point) fuel injection.
TBI Rebuild
Similar to a carburetor rebuild.
TDC
Top Dead Center. When the engine cylinder piston achieves its highest position within the cylinder.
Telescoping Gauge
Spring-loaded device for measuring inside dimensions (such as a cylinder bore).
Temperature Gauge Tester
Electronic device for testing accuracy of engine temperature gauge.
Tensile Strength
The amount of stretching a material can withstand before breaking.
Terminals
The positive and negative posts or threaded connectors on a battery.
Test Light
Device that will light up to show the presence of voltage (electrical
potential).
Test Light Code
Trouble code read by counting the flashes of a test light.
Thermal Efficiency
A comparison of fuel burned to horsepower output.
Thermo-Time Switch
Control circuit that energizes cold start injector when temperature is low enough.
Thermostatic Air Cleaner
System that heats the air being drawn through the engine air inlet to prevent carburetor icing.
Thermostatic Fan Clutch
Clutch that locks up for maximum airflow when it reaches operating temperature.
Thermostatic Spring
Bimetal coil spring that responds to engine heat and opens or closes the choke.
Thermostatic Switch
Electrical component that shuts off an air conditioning Compressor when the evaporator temperature approaches the freezing point.
Thermostat Rating
Temperature at which the thermostat opens.
Thread Pitch
Number of threads per inch or (metric sizes) distance between threads.
Throttle Body
Section of the carburetor containing the throttle valves.
Throttle Positioner
Device that works with idle air control valve in a TBI system to control idle speed.
Throttle Position Sensor Device that senses how much throttle is opening or closing.
Throttle Return Dashpot
Diaphragm device that prevents engine stalling when returning from high speed to idle operation.
Throttle Valve
Disc-shaped valve that controls airflow through the air horn.
Throw-Out Bearing
Bearing that decreases friction between clutch fork and pressure plate.
Thrust Bearing
Special bearings with flanges that limit crankshaft forward and rearward movement.
Thrust Washers
Metal pieces that can be slipped between block and crankshaft to limit endplay.
Tie Rod
Connectors between rack ends and steering knuckles.
Tightening Sequence
Recommended pattern for tightening multiple fasteners to obtain even tension.
Timed Injection
System timed to inject fuel as the intake valves open.
Timing Advance
Making the spark plug fire sooner in the compression stroke.
Timing Belt
Rubber belt performing the same job as timing chain or timing gears.
Timing Belt Cover
See Engine front cover.
Timing Belt Sprockets
Toothed wheels driving a cogged timing belt.
Timing Belt Tension
The proper degree of tightness; one that will transmit power efficiently without causing excessive belt wear.
Timing Belt Tensioner
Part performing same function as timing chain tensioner.
Timing Chain
Sprocket-and-chain combination that performs same function as timing gears.
Timing Chain Guide
Channel that helps support chain and prevents chain slap.
Timing Chain Tensioner
Spring-loaded plastic or fiber block that pushes on chain to eliminate slack.
Timing Gear Backlash
The amount of clearance between timing gear teeth.
Timing Gear Marks
Markings on differential ring and pinion gear sets that permit proper alignment.
Timing Gear Runout
The amount of wobble that occurs when gear is rotating.
Timing Gears
Meshing gears on crankshaft and camshaft that rotate camshaft at half crankshaft speed.
Timing Light
Strobe-like light that makes moving parts appear to stand still, allowing timing marks to be observed.
Timing Marks
Calibrating marks on timing gears or other timing devices.
Timing Retard
Making the spark plug fire later in the compression stroke.
Timing Sprockets
Gear-like toothed wheels used with timing chain.
Tire Bead
Wire ring, encased in rubber, that helps hold tire sidewall against the rim.
Tire Changer
Air-powered machine that automates many steps of tire changing.
Tire Gauge
Small instrument used to check inflation pressure of a tire.
Tire Impact Damage
Punctures, cuts, or tears caused by running over debris in road.
Tire Markings
Information shown on the sidewall to indicate inflation pressure, load carrying ability, size, and other data.
Tire Plug
Rubber insert sometimes used to repair punctures. The tire industry discourages the use of plugs under most circumstances.
Tire Ply
Layer of fabric or other material that forms the carcass or body of the tire.
Tire Rotation
Moving tires to different wheels periodically to even out wear.
Tire Wear Pattern
Areas of tread that are worn off, which can provide information on causes of the wear.
Toe
Degree to which opposing wheels are on converging or diverging lines (not parallel). Also, the narrow part of a gear tooth.
Toe-out On Turns
Steering feature that turns inside wheel more sharply than outside wheel.
Torque Converter
Fluid coupling that acts as a clutch on an automatic transmission.
Torque Multiplication
Variation in torque achieved by turning the impeller of a torque converter faster than the turbine.
Torque Specifications
Information on the correct amount of force to be applied in tightening a fastener.
Torque Tube
A solid steel drive shaft enclosed in a hollow tube, with a single swivel joint at the front.
Torque Wrench
A tool that is used to indicate the amount of force being applied to a fastener.
Torsion Bar
Spring steel rod that operates by twisting and untwisting.
Torsion Springs
Small coil springs that help absorb the shock and vibration that occur when the clutch engages.
Tracking
The position or direction of the front wheels in relation to the rear wheels.
Track Rod
Metal rod used to prevent axle side-to-side movement when cornering.
Tram Gauge
Instrument used to compare distances between the front and rear of a set of tires for toe adjustment.
Transaxle
A combination of transmission and differential in one case, used on front-wheel-drive vehicles.
Transaxle Differential
Transaxle assembly that transfers torque to driving axles and allows them to rotate at different speeds.
Transaxle Dipstick
Metal rod used to check level of lubricant in transaxle.
Transaxle External Adjustments
Clutch, shift linkage, bands, and other components often can be adjusted from outside the transaxle housing.
Transaxle Fill and Drain Plugs
Removable plugs that can be used to drain and refill lubricant in a transaxle.
Transaxle Filter
Replaceable element used to trap metal particles and other debris circulating with the lubricant.
Transaxle Gearbox
The transmission section of the transaxle, housing the forward and reverse gears.
Transaxle Input Shaft
Main shaft that turns the gears in a transaxle.
Transaxle Output Shaft
Shaft that transfers power to the ring and pinion gears of the differential.
Transaxle Pan
Lubricant sump at bottom of a transaxle.
Transducer
A device that changes an action or signal from one medium to another (an electrical pulse into a physical movement, for example).
Transfer Case
A power takeoff unit that sends power to both the front and rear axle assemblies on a four-wheel-drive vehicle.
Transfer Case Fill Plug
Removable plug to allow checking and adjusting of fluid level in the transfer case.
Transfer Pump
A small pump that supplies fuel to a diesel injector.
Transistor
Tiny electronic component that functions as a switch, but has no moving parts.
Transmission Case
Metal housing surrounding and supporting the transmission.
Transmission Cooler
A small separate radiator used to cool transmission oil in vehicles pulling heavy loads.
Transmission Diagnosis Chart
A diagnostic aid listing symptoms and probable causes.
Transmission ID Tag
A separate tag or set of' stamped numbers identifying the exact type of transmission being serviced.
Transmission Jack
A special tool used to support the weight of a transmission as it is being removed from a vehicle.
Transmission Linkage
System that connects the shift lever with the transmission shift forks.
Transmission Oil Cooler
Small tank within the radiator, used to regulate transmission fluid temperature.
Transverse
Crosswise; term used to identical an engine rotated 90 degrees from the traditional longitudinal mounting, typically found in front wheel drive cars.
Tread
Outer surface of tire that contacts the road.
Trigger Wheel
Rotating component with one tooth for each cylinder.
Tripod CV-Joint
Constant velocity joint used on front wheel drive vehicles, consisting of a spider and ball arrangement inside a housing.
Trouble Code Chart
Diagnostic aid that lists the trouble for each code.
Troubleshooting Chart
A guide that lists methods for finding and correcting vehicle problems.
Tubeless
Tire that does not have a separate inner tube to hold air.
Tumbler
Ignition switch lock mechanism.
Tune-Up Parts
Spark plugs, filters, and other periodic replacement items.
Turbine
The driven fan assembly in a torque convener.
Turbine Housing
The outer case that routes gases around the turbine wheel.
Turbine Wheel
A fan-like wheel driven by the exhaust gases of an engine. It turns a shaft and compressor wheel.
Turbo Bearing
Bearings supporting the turbo shaft.
Turbocharger
A form of supercharger that is driven by exhaust gases.
Turbo Lag
A short delay before turbo charging becomes effective.
Turbo Shaft
Shaft connecting turbine and compressor wheels in a turbocharger.
Turning
Term usually used for machining a brake drum or rotor, since process is carried out on a lathe.
Turning Radius Gauge
Instruments that measure how many degrees left or right the front wheels are turned.
Turn Signal Flasher
Bimetallic strip and heater unit that makes and breaks contact to cause on-off operation of the turn signals.
Twelve-Point
Box end wrench with twelve indentations, or gripping teeth.
Twin I-Beam
Double-axle suspension system used on some pickup truck models.
Two-Gas Analyzer
Measuring instrument that provides reading~ of NC and CO levels in exhaust.
Two-Stroke Cycle Engine
One that completes a full power-producing cycle with only one full crankshaft revolution.
U-Joint Alignment Marks
Scribed marks made on u-joint components before disassembly, allowing the joint components to be reassembled in the same positions to avoid possible imbalance and vibration.
Umbrella Valve Seal
Rubber or plastic seats that fit over opening at top of valve guide to keep oil out of them.
Under Inflation
Operating tire with a lower-than recommended air pressure.
Undersize Hearing
One designed for use on a crankshaft journal that has been machined to a smaller diameter.
Uni-Body:
A vehicle structure in which body and frame are one unit.
Universal Joint
A flex joint allowing limited up-and down and side-to-side movement.
Unleaded Gasoline
Fuel that does not contain lead-based antiknock additives.
Un-Sprung Weight
The weight of vehicle parts that are not supported by springs, such as the wheels.
Up-Date PROM
A PROXI with new programming that is plugged into the computer in place of the old one.
Vacuum
A pressure lower than atmospheric, in an enclosed area.
Vacuum Advance
System that provides additional ignition advance when engine load is low at medium throttle positions.
Vacuum Booster
Braking system booster actuated by vacuum.
Vacuum Choke Break
A device that uses vacuum to open and close the choke to prevent engine flooding at startup.
Vacuum Delay Valve
Mechanism that restricts airflow to slow down action of vacuum on a device.
Vacuum Gauge
Test instrument used to read negative pressure values.
Vacuum Leak
Loss of negative pressure due to crack or hole in a vacuum hose.
Vacuum Pump
A device that provides vacuum for operation of the engine accessories.
Vacuum Switch
One that opens or closes on a change in vacuum.
Vacuum Valve
Valve inside radiator cap that allows flow of coolant from recovery tank back into radiator.
Valve
Component that opens or closes a port to permit flow into and out of the combustion chamber.
Valve Adjusting Shims
Thin metal plates used to alter the cam-to-valve clearance.
Valve Adjustment
Correcting any malfunction in the opening and closing of valves actuated by mechanical lifters.
Valve Body
Housing containing most of the valves used in operation of an automatic transmission.
Valve Core
Threaded air valve that screws into place in a valve stem.
Valve Cover
A metal or plastic cover over the top of the cylinder head.
Valve Float
A tendency for valves to remain partly open, especially at high speeds. It usually results from a weak or broken valve spring.
Valve Grind Gasket Set
Set of gaskets needed for top end reassembly after valve grinding.
Valve Grinding
Process of machining a smooth surface on valve faces and valve stem tips.
Valve Guide
Holes machined into the engine block to support the valve stems as they slide up and down.
Valve Guide Cleaner
Rotating tool use to remove deposits from valve guides.
Valve Guide Insert
Replacing the worn guide with a new one.
Valve Guide Knurling
Grooving process that raises metal to restore inside diameter of guide.
Valve Job
Servicing of the cylinder head and valve train.
Valve Lifter
Component that is moved by the camshaft lobe and in turn moves the push rod or the rocker arm.
Valve Overlap
The short period when both valves in a cylinder are open.
Valve Reliefs
Indentations in a piston crown to provide valve clearance.
Valve Rotator
Device that turns the valve to prevent carbon buildup.
Valve Seal
Seals that fit over valve stems to prevent oil leakage.
Valve Seat
Machined surfaces on the intake and exhaust ports, against which the valve rests and seals.
Valve Seat Angle
The angle formed by the finished face of the seat.
Valve Seat Insert
One that is pressed into a recess cut into the head.
Valve Seat Reconditioning
Grinding or cutting valve seats to obtain a smooth surface.
Valve Seat Runout
Improper centering, so that the seat is not centered around the valve guide after
grinding or cutting.
Valves in Receiver
Expansion and POA valves enclosed within the receiver drier of an air conditioning system.
Valve Spring
Assembly that closes the valve when rocker arm pressure is removed.
Valve Spring Compressor
A Tool used to compress valve springs during disassembly.
Valve Spring Installed Height
The distance from top to bottom of the spring as installed in the cylinder head.
Valve Spring Seat
Cup-shaped washer that holds the bottom of the valve spring.
Valve Spring Shim
Precisely machined washer used to increase valve spring tension.
Valve Spring Shims
Thin metal pies used to adjust spring. tension after valve grinding.
Valve Spring Tester
Device for measuring the tension or pressure exerted by the spring.
Valve Stem
A rubber inflation tube with a threaded metal core that snaps into a hole on the rim of a wheel designed for use with tubeless tires.
Valve Stem Cap
Cap placed over end of valve stem to prevent stem wear.
Valve Stem
Seal
A seal placed over the end of the valve stem to prevent engine oil
from entering the combustion chamber
Valve Timing
Intervals at which valves open and close, determined by camshaft configuration.
Valve Train
The parts that operate the engine valves, camshaft, lifters, push rods, rocker arms, and springs.
Vaporization
A rapid change of state from liquid to gas.
Vapor Lock
Condition caused by bubbles in fuel due to overheating. Can cause stalling, hard starting, or failure to start.
Vapor Separator-Filter
Fuel filter that collects bubbles of vaporized fuel and returns them to the tank.
Variable Resistance Sensor
One with internal resistance that changes in response to changes in a condition (such as temperature).
Variable Venturi Carburetor
One in which the venturi size adjusts to maintain a constant air speed in the carburetor.
Vehicle Identification Number (VIN)
Individual number identifying a vehicle and displayed on a plate attached to the body.
Vehicle Maintenance Term for all operations performed to keep a vehicle in good running condition.
Vehicle Sensor
Device that changes a condition into an electrical signal that can be used as an input by a computer.
Venturi
Restriction (narrowed area) in air horn.
Vibration Damper
Heavy, rubber-mounted wheel on front of crankshaft to counter harmonic vibrations.
VIN
See Vehicle identification number.
Viscosity
A measure of the thickness, or ability to flow, of a lubricant.
Voice Alert System
Computer-based system that provides audible messages, in an electronically generated voice, to warn of safety problems or vehicle malfunctions.
Voltage
Electrical pressure that causes current flow.
Voltage Drop
Reduction of the amount of current flowing in a circuit.
Voltage Drop Tests
Starting system tests that identify parts showing high resistance.
Voltage Generating Sensor
One that changes voltage in response to external change.
Voltage Regulator
Device used to control alternator output.
VOM
Volt-ohm-milliammeter for determining electrical values.
V-type Engine
One with two banks of cylinders, arranged in a "V" configuration.
Wankel
A rotary engine with few moving parts.
Head
A head with a distorted (twisted or curved) surface as a result of overheating.
Waste Gate
A valve that limits the amount of boost developed by the turbocharger by venting excess exhaust gases.
Water Corrosion
Injector damage caused by the presence of water in diesel fuel.
Water Detector
Warning device that tells the driver there is water in diesel fuel.
Water Pump
A pump (usually of the centrifugal type) that circulates coolant through the engine and radiator of a vehicle.
Water Pump Rebuild
Process of disassembly, cleaning, parts replacement, and reassembling a water pump.
Wear Bar
Solid bars of rubber across the tread that appear when a tire has worn to the safe limit.
Wear Sleeve
Bushing between the axle and seal on a front-wheel drive vehicle.
Wedge Chamber
Combustion chamber with a triangular shape.
Wet Charged
Battery that is filled with electrolyte and fully charged at the factory.
Wet Compression Test
Test made by placing small amount of oil in a cylinder with a low reading, to determine whether worn rings are cause of low compression.
Wet Sleeve
A thick cylinder liner exposed to coolant.
Wheel Alignment
Adjusting wheels of a vehicle to roll in a straight line.
Wheel Balancing Machine
Device used to identify locations where weights must be placed to balance a tire.
Wheel Bearing
Ball or roller bearing assemblies that reduce friction as wheels or axles rotate.
Wheel Brake Assemblies
Components that use hydraulic pressure to apply friction for stopping vehicle.
Wheel Cover
Metal or plastic disk designed to fit over center section of wheel for better appearance.
Wheel Cylinder
Hydraulic piston that actuates braking at each wheel.
Wheel Cylinder Rebuild
Process that typically involves honing the cylinder and replacing all rubber parts (cups and boots).
Wheel Hop
A bouncing or up-and-down movement.
Wheel Puller
A device used to remove pressed-on parts, such as gears.
Wheel Shimmy
A side-to-side movement caused by dynamic imbalance.
Wheel Speed Sensors
Magnetic pickups to detect wheel speed (used on anti~lock braking systems).
Wheel Weight
Small pieces of lead that are clipped to the wheel rim to balance the wheel and tire combination.
Wiggle Test
Physically moving wires and connectors to locate broken wires or other causes of
intermittent problems.
Winding
Loop of wire on a motor armature that generates a magnetic field.
Wire Wheel
Cleaning tool with wires arranged radially, rotated at moderately high speed to remove carbon deposits from parts.
Wiring Diagram
Drawings that show relationships of components in an electrical circuit.
Wiring Harness
A group of primary wires enclosed in a protective plastic covering.
Work
The result of force causing movement; measured in foot-pounds, watts, or joules.
Worm Shaft
Input gear in a re-circulating ball gearbox.
Worn Cam Bearings
After prolonged engine use, this condition can cause reduced oil pressure.
Worn Idler Arm
Condition that can cause steering wheel play.
Worn Piston Rings
Many engine problems arc caused by failure of worn rings to properly seal against cylinder walls.
Worn Rocker Arms
Primarily cause noise (valve clatter).
Worn Tie Rod End
A cause of excessive play in the steering wheel.
Worn Timing Chain
Permits slack between camshaft and crankshaft sprockets, so valves no longer keep proper timing with the pistons.
Worn Joint
Excessive play between the cross and yoke.
Worn Valve Guide
Enlarged guide that allows valve to move excessively, causing various engine problems.
WOT Switch
Device that shuts off air conditioning compressor.
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