Master the Language and Systems of ASE Certification with Key Terminology—Now Included with Every ASE Test Prep Plan

Air Filter

A component that removes dust, pollen, and other particulates from the air before it enters the engine for combustion. Air filters ensure optimal performance and prevent abrasive wear on the engine.

Balance Shaft

An engine component that is used to reduce vibration by counterbalancing rotational forces within the engine. Positioned parallel to the crankshaft, it rotates at twice the crankshaft’s speed to provide smoother operation. Also applies to Counterbalance Shaft.

Camshaft

A rotating shaft within the engine that opens and closes the intake and exhaust valves in sync with the pistons. The camshaft is driven by the crankshaft via a timing belt or chain and features lobes that push against valve lifters to control valve movement.

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Camshaft Bearings

These are precision-made smooth surfaces or sleeves inside the engine block that support and reduce friction for the camshaft as it rotates.

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Camshaft Bore

The cylindrical opening in an engine block that houses the camshaft. The camshaft bore must be precisely machined to maintain the correct alignment and clearance for the camshaft.

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Camshaft Bore Alignment

This term refers to the proper geometric alignment of the camshaft bores in an engine block, ensuring the camshaft rotates without excessive friction or wear.

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Camshaft Bore Out-Of-Round

This describes a condition where the camshaft bore deviates from a perfect circular shape. It can lead to improper camshaft operation and increased wear.

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Camshaft Bore Wear

Wear inside the camshaft bore, which can result from inadequate lubrication, debris, or high operating temperatures, leading to increased clearances and potential engine damage.

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Camshaft Journals

The sections of the camshaft that rest on the bearings, providing a smooth, hardened surface to reduce friction and wear.

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Camshaft Lift

The height by which a camshaft lobe lifts the valve off its seat during operation. This is critical for controlling the air and fuel mixture intake and exhaust gas expulsion.

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Camshaft Lobes

Protrusions on the camshaft that press against followers or lifters to open valves at the correct intervals. Each lobe is designed with a specific profile to control how the valve opens and closes.

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Connecting Rod

A rod that connects the piston to the crankshaft, transferring motion and force from the piston to the crankshaft.

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Coolant Dye Test

A diagnostic procedure that involves adding a fluorescent dye to the engine’s coolant to detect leaks. Under UV light, the dye shows the precise location of coolant leaks.

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Coolant Recovery System

A system that collects overflowing coolant caused by heating and returns it to the radiator as the engine cools, preventing coolant loss and maintaining coolant level.

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Cooling System Pressure Test

A test performed to check the integrity of the cooling system by pressurizing it to ensure there are no leaks and that the pressure cap functions properly.

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Core And Gallery Plug

Plugs used to seal the openings left after casting the engine block. They help contain the coolant and oil within their respective passages.

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Counterbalance Shaft

An engine component that is used to reduce vibration by counterbalancing rotational forces within the engine. Positioned parallel to the crankshaft, it rotates at twice the crankshaft’s speed to provide smoother operation. Also applies to Balance Shaft.

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Cranking System

The system on an engine that facilitates its initial start-up, including components the battery, starter motor and solenoid, and ignition switch.

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Crankshaft

The main rotating shaft of an engine, which converts the linear motion of pistons into rotational motion that is transmitted to the drivetrain.

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Crankshaft Flange

The rear end of the crankshaft where the flywheel or flexplate are mounted.

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Crankshaft Girdle (Bed Plate/Ladder)

A structural component that sits below the crankshaft, adding rigidity to the engine block and helping to secure the main bearings.

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Crankshaft Reluctor Ring/Tone Wheel

A component attached to or part of the crankshaft that interacts with sensors to provide position and speed information to the engine control unit (ECU).

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Customer Concern

Any issue or complaint reported by the customer regarding the vehicle’s performance, often the starting point for diagnostic processes.

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Cylinder Compression Test

A diagnostic test used to measure the pressure within an engine’s cylinders when the piston compresses the air-fuel mixture, indicating the condition of the engine’s valves, piston rings, and cylinder walls.

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Cylinder Head

The component that sits above the cylinders on top of the cylinder block. It houses the combustion chambers, intake and exhaust valves, and spark plugs in a spark-ignition internal combustion engine. Also applies to Cylinder Heads. Also applies to Cylinder Heads.

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Cylinder Heads

The components that sit above the cylinders on top of the cylinder block. They house the combustion chambers, intake and exhaust valves, and spark plugs in a spark-ignition internal combustion engine. Also applies to Cylinder Head.

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Cylinder Leakage/Leak-Down Test

Diagnostic test that measures the ability of the cylinder to hold pressure. They help identify problems like worn piston rings, damaged valves, or head gasket failures.

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Cylinder Power Balance Test

A diagnostic test that assesses the contribution of each cylinder to the engine’s power output. It helps identify cylinders that are underperforming due to mechanical issues like compression loss, ignition problems, or fuel delivery deficiencies.

Damper/Harmonic Balancer

A device fitted to the crankshaft of an engine to reduce mechanical vibrations and serve as a pulley for drive belts.

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Drive Belt

A belt that transmits power from the crankshaft to other components like the alternator, water pump, and air conditioning compressor.

Electrical Water Pump

A pump powered by electricity rather than by the engine directly, offering more precise control over coolant flow based on engine temperature and performance demands.

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Endplay

The axial movement or freedom of movement of a shaft within its supporting bearings. Controlling endplay is essential for proper mechanical clearances and operation.

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Engine Assembly

The complete build-up of the engine including all internal components like the crankshaft, camshaft, connecting rods, pistons, and cylinder heads, assembled as a unit.

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Engine Block

The main structure of an engine, typically made of cast iron or aluminum, housing the cylinders and other components of the internal combustion engine.

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Exhaust Manifold

A conduit that collects exhaust gases from multiple cylinders into one pipe, directing them towards the exhaust system.

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Exhaust System

A series of pipes and chambers designed to channel exhaust gases away from the engine compartment and reduce noise and emissions.

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External Engine Oil Cooler

A device that reduces engine oil temperature by allowing oil to circulate through a heat exchanger typically located outside the engine block.

Filter Housing

The casing that contains a filter (oil, fuel, air) and integrates it into the system, ensuring an airtight and fluid-tight seal.

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Flexplate

A metal disc connected to the crankshaft that transfers torque from the engine to the torque converter in automatic transmissions.

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Flywheel Runout

The deviation or wobble of a flywheel from its central axis during rotation, which can cause vibration and affect engine balance.

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Formed-In-Place (Tube-Applied) Sealants

Sealants applied directly from a tube to gaskets or mating surfaces in an engine to prevent leaks of fluids or gases.

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Fuel Injection

A system that injects fuel directly into the combustion chamber or intake airflow before it enters the chamber, improving the efficiency and control of the engine’s fuel usage.

Gallery Plug

A plug used to seal oil or coolant passages in an engine block or other components, ensuring fluid integrity within the engine.

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Gaskets

Sealing materials placed between two engine parts to prevent leakage of fluids and gases, critical for maintaining compression.

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Gasoline Direct Injection (GDI)

A form of fuel injection used in modern engines where fuel is injected directly into the combustion chamber at high pressure, providing better control over the combustion process.