Know your
car.

The core structural component of the engine. A large metal casting — usually iron or aluminium — that houses the cylinders, pistons, and coolant passages. All other engine components bolt directly to it.

Sits on top of the engine block and seals the combustion chambers. Contains the intake and exhaust valves, camshaft(s), and spark plug ports. A blown head gasket (the seal between block and head) causes overheating and coolant loss.

Cylindrical components that move up and down inside the cylinders. As fuel combusts, expanding gases push the piston downward, converting combustion energy into rotational motion via the crankshaft.

Converts the up-and-down (reciprocating) motion of the pistons into rotational motion. Runs along the bottom of the engine block and connects to the gearbox via the flywheel. Bent or broken crankshafts are usually caused by hydraulic lock or catastrophic over-rev.

Controls the opening and closing of the engine's intake and exhaust valves. Driven by the crankshaft via a timing belt or chain. Overhead camshaft (OHC) engines mount the camshaft in the cylinder head for more precise valve control.

Also: cam belt

Links the crankshaft to the camshaft, ensuring valves open and close in perfect sync with piston movement. Rubber belts must be replaced at manufacturer-specified intervals — a snapped belt typically destroys the engine. Timing chains are metal and longer-lasting but can stretch.

Distributes air (or air/fuel mixture on carburetted engines) from the throttle body to each cylinder's intake port. A cracked or leaking intake manifold causes a vacuum leak, resulting in rough idle, poor performance, and increased fuel consumption.

Provides the electrical spark that ignites the compressed air-fuel mixture inside the combustion chamber. Worn spark plugs cause misfires, poor fuel economy, and rough running. Most modern vehicles use iridium or platinum plugs that last 80,000–160,000 km.

The seal sandwiched between the engine block and cylinder head. Prevents combustion gases, engine oil, and coolant from mixing or leaking externally. A "blown" head gasket is one of the most serious engine failures — symptoms include white smoke from the exhaust, milky oil, unexplained coolant loss, and overheating.

Also: NA or normally aspirated

An engine that draws air into the cylinders using only the suction of the pistons (atmospheric pressure), without forced induction from a turbocharger or supercharger. Generally more reliable and linear in power delivery, but produces less power per litre than turbocharged equivalents.

Also: poppet valve

Intake and exhaust valves control airflow into and out of each cylinder. Opened by the camshaft and closed by valve springs. Most modern engines run four valves per cylinder (two intake, two exhaust) for better breathing. Burnt or damaged valves cause compression loss, misfires, and a noticeable drop in power.

Also: VVT — also VTEC (Honda), VANOS (BMW), VVT-i (Toyota)

A system that adjusts when the intake and/or exhaust valves open and close relative to piston position, varying with engine speed and load. Improves low-rpm torque, high-rpm power, fuel economy, and emissions simultaneously. A faulty VVT system usually causes rough idle, poor low-end response, and a check engine light.

Also: turbo

Forces more air into the cylinders by using exhaust gas energy to spin a turbine and compress the intake air. More air means more fuel can be burnt, producing significantly more power from a smaller engine. A failing turbo may produce blue or black smoke, a loss of boost, and a distinct whine or rattle.

Also: rotor

A flat metal disc that rotates with the wheel. Brake pads clamp against it to create friction and slow the vehicle. Can warp from heat or wear thin over time — a warped disc causes pulsing or vibration through the brake pedal.

Friction material bonded to a steel backing plate that presses against the brake disc when you apply the brakes. Wear down over time. Most have a built-in wear indicator that emits a high-pitched squeal when replacement is due. Ignoring this leads to metal-on-metal contact and disc damage.

The hydraulic clamp that squeezes the brake pads against the rotor. Hydraulic pressure from the master cylinder activates a piston (or multiple pistons) inside the caliper. Seized calipers cause uneven braking, premature pad wear, and the vehicle pulling to one side under braking.

Also: brake pipes

Steel pipes and flexible rubber hoses that carry brake fluid from the master cylinder to each wheel's caliper or drum cylinder. Any leak in the system causes a loss of braking pressure. Rubber brake hoses deteriorate internally over time and should be replaced at service intervals.

Also: Anti-lock Braking System

Prevents the wheels from locking up during hard braking, allowing the driver to maintain steering control. Wheel speed sensors detect a skidding wheel and rapidly modulate brake pressure multiple times per second. Standard on all modern vehicles and mandatory in most markets.

Also: vacuum servo

Uses engine vacuum (or an electric pump on hybrids and EVs) to amplify the force you apply to the brake pedal, making braking easier. A failing brake booster makes the pedal feel hard and requires significantly more leg force to achieve the same braking effect.

Also: parking brake or emergency brake

A mechanically operated brake — usually a cable pulling on the rear brakes — used to hold the vehicle stationary when parked. Unlike the hydraulic foot brake, it operates independently and can serve as a backup in the event of brake failure. Modern vehicles increasingly replace the lever with an electronic parking brake (EPB) button.

A thin metal plate fitted behind the brake disc or along the exhaust system to deflect heat away from surrounding components. Brake heat shields protect brake hoses and wheel bearings; exhaust heat shields protect the vehicle floor, fuel lines, and underbody components. Loose heat shields cause a rattling noise, especially when cold.

Also: damper

Controls the movement of the suspension spring, preventing the vehicle from bouncing excessively after hitting a bump. Contains hydraulic fluid that is pushed through small valves to dampen oscillation. Worn shocks cause excessive body movement, longer stopping distances, and uneven tyre wear.

A helical steel spring that absorbs road impacts and supports the vehicle's weight. Works alongside the shock absorber. A broken coil spring causes the vehicle to sit lower on one corner, affects handling, and can damage the tyre by allowing metal-to-metal contact.

Also: A-arm or wishbone

A hinged suspension link that connects the wheel hub to the vehicle's chassis, allowing the wheel to move up and down while keeping it properly aligned. Worn control arm bushings cause imprecise handling and clunking noises over bumps.

A spherical bearing that connects the control arm to the steering knuckle, allowing rotation in multiple directions simultaneously. Worn ball joints cause clunking over bumps and wandering steering. A completely failed ball joint can cause the wheel to detach — a safety-critical failure.

Connects the steering rack to the wheel hub, translating steering input into wheel movement. Consists of inner and outer tie rod ends. Worn tie rods cause loose, imprecise steering, a wandering vehicle, and rapid uneven tyre wear. Replacement requires a wheel alignment afterwards.

Also: anti-roll bar or stabiliser bar

A metal bar that connects the left and right sides of the suspension, resisting body roll when cornering. Worn sway bar bushings or end links cause a clunking noise over bumps and excessive body lean through corners.

A suspension spring made from stacked curved steel strips (leaves) clamped together. Common on the rear axles of pickup trucks, vans, and older vehicles. Robust and capable of handling heavy loads, but provides a firmer ride than coil springs. Worn or broken leaves cause sagging, uneven ride height, and clunking.

Also: steering knuckle or upright

The pivoting component that connects the wheel hub, brake assembly, and suspension links (control arm, strut) to the steering system. The wheel rotates around the hub mounted to the knuckle. Bent or cracked knuckles — often the result of serious kerb or pothole impacts — require immediate replacement.

Stores electrical energy and provides the high current needed to crank the starter motor. Also powers all electrical components when the engine is off. Most vehicles use a 12V lead-acid battery. Typical lifespan is 3–5 years — hot climates accelerate deterioration.

Generates electricity while the engine is running, recharging the battery and powering all electrical systems. Driven by a belt connected to the engine. A failing alternator causes progressive battery drain, dimming headlights, and eventually a dead vehicle.

An electric motor that cranks the engine to start it. Draws very high current from the battery for a few seconds at a time. A faulty starter may cause a clicking sound (low battery or bad solenoid), grinding (worn drive gear), or complete silence when you turn the ignition key.

Also: fusebox or fuse panel

Contains fuses and relays that protect the vehicle's electrical circuits from overloads. A blown fuse cuts power to an entire circuit. Always check the fuse box first when any electrical component stops working — it's the first diagnostic step before more expensive investigations.

Also: diagnostic port

On-Board Diagnostics (OBD-II) port, standardised on all vehicles sold since 1996. Allows diagnostic scanners to read fault codes (DTCs) stored by the ECU. Located under the dashboard on the driver's side. The source of the check engine light codes your mechanic retrieves.

Also: Engine Control Unit or Engine Control Module (ECM)

The main computer that manages engine operation in real time. Monitors dozens of sensors — oxygen sensor, throttle position, coolant temperature, MAF sensor — and adjusts fuel injection timing, ignition advance, and other parameters accordingly. A faulty ECU typically triggers multiple fault codes simultaneously.

Also: jump-starting or boosting

The process of starting a vehicle with a flat or discharged battery by temporarily connecting it to a charged 12V source — another vehicle or a portable jump pack — using jump leads. Incorrect connection order (positive first, then negative; remove negative first) can damage sensitive electronics or cause a spark near the battery.

Detects engine knock — the sound of fuel igniting prematurely in the combustion chamber before the spark plug fires (also called pinging or detonation). Sends feedback to the ECU, which retards ignition timing to protect the engine. A failed knock sensor causes reduced power, poor fuel economy, and a check engine light.

Also: transmission

Transmits engine power to the driveshaft at different gear ratios to suit varying driving conditions — low gears for acceleration, high gears for cruising efficiency. Manual gearboxes use a driver-operated clutch; automatics use a torque converter and hydraulic control system.

In a manual gearbox, temporarily disconnects the engine from the gearbox to allow smooth gear changes. Consists of a clutch disc, pressure plate, and release bearing. A worn clutch slips under load — the engine revs rise but the vehicle doesn't accelerate proportionally.

Also: propshaft

Transmits rotational power from the gearbox to the differential (rear-wheel drive) or directly to the driven wheels (front-wheel drive). Equipped with CV joints or universal joints to accommodate suspension movement and steering angles.

Also: diff

Allows the driven wheels to rotate at different speeds when cornering — essential because the outer wheel travels further than the inner wheel. Limited-slip differentials (LSDs) restrict speed difference under power for improved traction. A failing diff produces a whining or howling noise.

Also: Constant Velocity Joint

A flexible coupling that transmits power to the wheels at a constant rotational speed regardless of the steering angle or suspension position. Critical in front-wheel drive vehicles. A worn CV joint makes a distinctive clicking noise when turning under acceleration.

A heavy rotating disc bolted to the crankshaft that stores rotational energy to smooth out engine power pulses between combustion strokes. Also provides the surface for the clutch disc to engage and carries the ring gear that the starter motor engages to crank the engine.

Also: U-joint or Cardan joint

A flexible coupling that allows a driveshaft to transmit rotational power through an angle. Unlike a CV joint, a single U-joint causes a slight speed variation as it rotates at an angle — rear-wheel drive propshafts use two U-joints in opposing phase to cancel this effect. Worn U-joints produce a clunking or vibration under acceleration.

The main heat exchanger in the cooling system. Hot coolant flows through a matrix of narrow tubes and fins; airflow from driving or the electric fan removes the heat. A blocked, leaking, or damaged radiator is the most common cause of engine overheating.

A temperature-controlled valve that regulates coolant flow. Stays closed when the engine is cold (helping it warm up quickly) and opens when the engine reaches operating temperature, allowing coolant to flow to the radiator. A stuck-open thermostat causes the engine to never reach operating temperature; stuck-closed causes rapid overheating.

Circulates coolant through the engine block, cylinder head, and radiator. Usually driven by the timing belt or a separate accessory belt. A failing water pump causes overheating and typically makes a whining or rumbling noise from the front of the engine.

Also: antifreeze

A mixture of ethylene glycol antifreeze and water (typically 50/50) that absorbs heat from the engine and carries it to the radiator. Also provides freeze protection, raises the boiling point of the system, and prevents internal corrosion. Requires flushing and replacement at specified intervals.

Seals the cooling system and maintains a set pressure (typically 1.0–1.3 bar). Pressurising the system raises the coolant's boiling point, improving efficiency. A faulty radiator cap causes coolant to boil and overflow at lower temperatures, appearing as overheating.

Collects hot exhaust gases exiting each cylinder and channels them into a single pipe leading to the rest of the exhaust system. Usually cast iron or stainless steel. A cracked manifold causes a ticking noise (louder on cold start) and can allow toxic exhaust gases into the engine bay.

Also: cat or cat converter

Reduces harmful exhaust emissions by converting carbon monoxide, unburnt hydrocarbons, and nitrogen oxides into less harmful carbon dioxide, water, and nitrogen. Contains precious metals (platinum, palladium, rhodium) — making them high-value theft targets. A failing cat causes a sulphur smell and failed emissions tests.

Also: silencer

Reduces exhaust noise using internal chambers, perforated tubes, and baffles that cancel out sound waves. A rusted or holed muffler causes excessive exhaust noise and may allow exhaust gases to enter the passenger cabin — a carbon monoxide risk.

Also: O₂ sensor or lambda sensor

Measures the oxygen content in the exhaust gases and sends feedback to the ECU to fine-tune the air-fuel mixture in real time. A faulty oxygen sensor causes poor fuel economy, rough running, failed emissions tests, and illuminates the check engine light.

Also: Diesel Particulate Filter

Traps soot particles from diesel exhaust to reduce air pollution. Periodically self-cleans through a process called regeneration — burning off trapped soot at high temperature during sustained motorway driving. A blocked DPF causes significant power loss, increased fuel consumption, and a DPF warning light.

The side of the tyre between the tread and the wheel bead. Contains important information: tyre size, load index, speed rating, and DOT manufacture date. Sidewall damage — bulges, cuts, or cracks — is a serious safety risk requiring immediate replacement; the tyre can fail without warning.

The depth of the grooves in the tyre tread, measured in millimetres. Legal minimum in most markets is 1.6mm — Spanna recommends replacing at 3mm for safety. At 1.6mm tread, wet-weather stopping distances can be up to 40% longer compared to a new tyre.

Also: tracking

The adjustment of wheel angles — camber (vertical tilt), toe (horizontal angle), and caster (steering axis tilt) — relative to each other and the vehicle. Poor alignment causes rapid, uneven tyre wear, vehicle pulling to one side, and poor fuel economy. Must be checked after any suspension work or kerb strike.

Moving tyres from one position on the vehicle to another — typically front to rear — at regular intervals to promote even wear across all four tyres. Front tyres wear faster on front-wheel drive vehicles due to combined steering and driving loads. Recommended every 8,000–12,000 km.

Adding small counterweights to the wheel to ensure it spins evenly without vibration. An out-of-balance wheel causes steering wheel vibration (typically at specific speeds), accelerated tyre wear, and stress on wheel bearings and suspension components. Should be done whenever new tyres are fitted.

Reinforced areas on the vehicle's underside, specified in the owner's manual, where a jack must be positioned to safely lift the vehicle. Placing a jack elsewhere can crush the sill, crack the floor pan, or cause the vehicle to slip off the jack dangerously. Vehicles also have dedicated axle stands positions for sustained lifting.

Also: wheel nut

The threaded fasteners that secure the wheel to the hub. Must be tightened in a star pattern to the manufacturer's specified torque using a torque wrench. Overtightening warps brake discs and makes the nuts impossible to remove; undertightening risks the wheel coming loose while driving.