Craftsman Motor Vehicles Maintenance key terms

A calibrated tool that tightens a fastener to a specified turning force, then signals when that value is reached, preventing stripped threads and warped components from guesswork or over-tightening.

The manufacturer's stated tightening force for a fastener, often given as a value plus an angle. It depends on thread size, material, and whether the fastener is dry or lubricated.

A safety procedure that isolates energy sources such as battery, fuel, or compressed air and attaches a warning tag so equipment cannot be restarted while someone is working on it.

Wearable gear such as safety glasses, gloves, hearing protection, and steel-toe boots that reduces injury risk from flying debris, hot surfaces, noise, and chemical splash in the workshop.

A document supplied with a chemical product that lists its hazards, safe handling, first-aid measures, and storage requirements, and must be accessible to everyone who uses the product.

A number such as 5W-30 describing how thick an oil is when cold and hot. The first figure reflects cold flow, the second reflects thickness at operating temperature.

A gear, rotor, or vane device driven by the engine that draws oil from the sump and pushes it under pressure through galleries to bearings and the valve train.

A dashboard indicator that illuminates when measured oil pressure falls below a safe threshold, warning of low level, a failing pump, or worn bearings that could destroy the engine.

A system that routes blow-by gases from the crankcase back into the intake to be burned, reducing emissions and preventing pressure from forcing oil past seals.

A temperature-controlled valve in the cooling circuit that stays closed while the engine warms and opens at a set temperature to send coolant through the radiator.

A radiator or expansion-tank cap containing a spring valve that raises the boiling point of coolant by holding system pressure, then vents to relieve overpressure.

The ratio of antifreeze to water in the cooling system, which sets freeze protection, boil-over margin, and corrosion-inhibitor strength and must be checked with a refractometer.

A short-term and long-term percentage by which the engine computer adjusts fuel delivery to reach the target air-fuel ratio, revealing vacuum leaks or failing injectors when it drifts.

A device in the intake tract that measures the mass of air entering the engine so the computer can calculate the correct fuel quantity for combustion.

A valve that bypasses exhaust gas around the turbine to limit boost pressure, protecting the engine from over-boost and detonation at high load.

Combustion gas that escapes past worn piston rings or cylinder walls into the crankcase, raising internal pressure and often carrying oil mist into the intake.

A diagnostic measurement of peak cylinder pressure during cranking, used to find leaking valves, worn rings, or a blown head gasket by comparing cylinders.

A test that pressurizes a cylinder at top dead center and measures the percentage of air escaping, with the leak location revealing valve, ring, or gasket faults.

The prescribed order and stages for tightening head bolts so the gasket seals evenly and the head does not distort, often ending with a specified torque angle.

The small gap between the cam lobe or rocker and the valve stem, which must be set to the maker's figure so valves open fully and close tightly when hot.

The synchronized relationship between crankshaft position and camshaft position, which determines when valves open relative to piston movement and must be correct for the engine to run.

A toothed belt that drives the camshaft from the crankshaft at an exact ratio; it must be replaced at the maker's interval because failure causes valve and piston collision.

The lined plate between flywheel and pressure plate that transmits engine torque to the gearbox by friction and slips when the pedal is pressed.

The small amount of pedal or release-bearing travel before the clutch begins to disengage, needed so the bearing is not loaded while the clutch is engaged.

A flywheel split into two masses joined by springs and a bearing, which damps driveline vibration and can fail with rattles or judder if the springs wear.

A joint in a driveshaft that transmits power smoothly through a range of angles, common at the wheel end of front-drive axles and protected by a rubber boot.

The small clearance between ring gear and pinion teeth that allows lubricant film and thermal expansion; too much causes whine, too little causes seizure.

The tendency of brake fluid to absorb water from the air over time, which lowers its boiling point and can cause vapour lock and a spongy pedal under heavy braking.

The process of removing trapped air from hydraulic brake lines by opening a bleeder screw and pushing fresh fluid through until no bubbles appear.

A loss of braking force when friction material or fluid overheats, felt as a long or soft pedal and reduced stopping power during repeated hard use.

An electronic system that rapidly modulates brake pressure at each wheel to prevent lock-up, preserving steering control during hard stops on low-grip surfaces.

A magnetic or Hall-effect device at each wheel that reports rotation speed to the ABS and stability computers, and whose failure disables those systems.

The adjustment of camber, caster, and toe so wheels point correctly relative to the vehicle and road, preventing uneven tyre wear and steering pull.

The shape and location of wear across a tyre tread, which points to misalignment, incorrect inflation, worn suspension, or balance faults when read correctly.

The even distribution of mass around a wheel and tyre, corrected with weights so that centrifugal force does not cause vibration at speed.

A hydraulic damper that converts suspension movement into heat, controlling spring oscillation and keeping the tyre in contact with the road over bumps.

A probe in the exhaust stream that measures residual oxygen and feeds the engine computer, which uses it to correct fuel mixture and monitor catalytic converter efficiency.

The vehicle's self-test system that stores fault codes and live data for engine and chassis systems, read through a diagnostic connector with a scan tool.

A low-voltage safety circuit threaded through high-voltage connectors on hybrid and electric vehicles that disables the traction battery if a connector is opened.

Current drawn from the battery while the vehicle is switched off, which should be low; excess drain from a faulty module or lamp flattens the battery overnight.

A check that applies a heavy current draw to a battery and measures whether voltage holds above a minimum, showing whether it can still crank the engine.

A structured check of a vehicle before handover covering fluid levels, tyre pressures, lights, and safety items, with findings recorded on a signed checklist.

A written list of items to examine in a fixed order so that no safety or maintenance point is missed, and so results can be compared over time.

A controlled drive after repair or during diagnosis to confirm symptoms, verify the fix, and check braking, steering, and drivability under real conditions.

A questioning technique that asks why a fault occurred repeatedly, moving from the visible symptom to the underlying process or design cause so the repair addresses the root.

The step of reproducing or confirming the customer's described symptom before any repair, so the technician knows the fault is real and can prove it is fixed.

The written record of a job that lists the customer concern, approved work, parts used, labour time, and findings, and serves as the legal and billing document.