The engine turns the energy of burning fuel into rotation that drives the vehicle. Here you will find aftermarket replacements for internal parts (pistons, bearings, timing, valves), gaskets, accessories, sensors and ignition parts for gasoline and diesel engines in American vehicles.
In this guide: Air filters, Axle locker actuators, Crankshafts, Cylinder head bolts, Cylinder heads, Engine bearings, Engine bolts, Engine gaskets, Engine mounts, Engine sensors, Fuel injection and delivery, Fuel pressure sensors, Ignition coils, Intake air temperature sensors, Manifolds, Oil filters, Oil pans, Oil pressure sensors, Oil pumps, Piston rings, Pistons, Pulleys and accessories, Spark plugs, Thermostats, Throttle position sensors, Timing components, Valve lifters, Valves and cylinder head parts, Water pumps.
Air filters
What it is: The filter cleans the air drawn into the engine of dust and sand. Dirt that gets into the cylinders acts like an abrasive on the pistons and rings.
Where it is fitted: In the air filter box at the start of the intake system, usually in the engine bay.
Signs of wear: A clogged filter reduces power and increases fuel consumption; replace it per the service schedule or sooner in dusty conditions.
Did you know: Off-road and on gravel roads the filter clogs much faster, so check it more often than the schedule suggests.
Axle locker actuators
What it is: An actuator that engages the differential locker or connects the drive in the axle at the driver's command. It lets both wheels on an axle turn together, which helps in difficult terrain.
Where it is fitted: Mounted on the drive axle housing, next to the differential.
Signs of wear: Replace it when the locker will not engage or disengage, the locker indicator keeps flashing, or you can hear the actuator working with no effect.
Did you know: Use the locker only off-road at low speed, and engaging it now and then, even when not needed, reduces the risk of the mechanism seizing.
Crankshafts
What it is: The crankshaft converts the up-and-down motion of the pistons into rotation that goes through the transmission to the wheels.
Where it is fitted: In the lower part of the engine block, running in the main bearings.
Signs of wear: It needs replacing or grinding after a bearing failure, when the journals are scored or out of round, or if it is cracked.
Did you know: During a rebuild, check crankshaft runout and end play, and use undersize bearings after the journals are ground.
Cylinder head bolts
What it is: Head bolts or studs clamp the cylinder head to the block with high, even force so the head gasket can hold combustion pressure.
Where it is fitted: They pass through the cylinder head and thread into the engine block.
Signs of wear: Replace them every time the head is removed and the head gasket is changed, if they are single-use.
Did you know: Most modern head bolts are tightened to a torque and then by a set angle in a specific sequence; they are torque-to-yield, so they must not be reused.
Cylinder heads
What it is: The cylinder head closes the cylinders from above and forms the combustion chambers. It houses the valves and, on most modern engines, the camshafts, intake and exhaust ports and coolant passages.
Where it is fitted: Bolted to the top of the engine block over the head gasket.
Signs of wear: Replacement or repair is needed after overheating, when it is cracked, when coolant disappears with no visible leak, or when oil and coolant mix.
Did you know: Aluminium heads warp easily after overheating, so check flatness before refitting and have the surface machined if needed.
Engine bearings
What it is: Bearings are thin plain shells on which the crankshaft turns (main bearings) and the connecting rods run (rod bearings). An oil film is kept between them and the shaft.
Where it is fitted: In the engine block in the crankshaft saddles, and in the big ends of the connecting rods.
Signs of wear: Wear shows up as a knock from the bottom of the engine that grows under load, and as a drop in oil pressure.
Did you know: Bearings must match the journal size: after the crankshaft is ground, undersize bearings are needed instead of standard ones.
Engine bolts
What it is: Bolts that hold engine components such as pulleys, manifolds, covers or the flywheel. They must withstand vibration and temperature changes without loosening.
Where it is fitted: In various places on the engine, depending on the part they hold.
Signs of wear: Replace them when the thread is stripped or damaged, they are corroded or cracked, and always when the manufacturer specifies them as single-use.
Did you know: Some engine bolts, such as the crank pulley or flywheel bolts, are single-use because they stretch when torqued and will not clamp properly a second time.
Engine gaskets
What it is: Gaskets prevent oil, coolant and exhaust leaks at the joints between engine parts. This group includes head gaskets, valve cover, oil pan and manifold gaskets, and shaft seals.
Where it is fitted: At the joints between engine parts: between head and block, under covers, the oil pan and the manifolds.
Signs of wear: Signs are oil leaks and spots, coolant loss, exhaust smell, and for a head gasket white smoke, overheating and fluids mixing.
Did you know: Mating surfaces must be clean and dry, and no sealant should be added to gaskets that the manufacturer specifies to be fitted dry.
Engine mounts
What it is: Mounts attach the engine to the frame or body and absorb its vibration so it does not reach the cabin. They also hold the engine in place when pulling away and braking.
Where it is fitted: Between the engine block and the frame or crossmember, usually on both sides of the engine.
Signs of wear: Worn mounts cause clunks when pulling away or changing direction, strong vibration at idle, and visibly cracked rubber or a leaking hydraulic mount.
Did you know: Wear is easy to check with a helper: holding the brake, shift the automatic between D and R with a little throttle and watch whether the engine lifts noticeably.
Engine sensors
What it is: A broad group of sensors that feed the engine computer with data on how the engine is running, such as crankshaft and camshaft position, coolant temperature, manifold pressure and knock. The computer uses them to control injection and ignition.
Where it is fitted: Located in various places on the engine: in the block, cylinder head, intake manifold, thermostat housing and near the flywheel.
Signs of wear: A failed sensor usually turns on the check engine light and stores a fault code; depending on the type it can cause stalling, hard starting, limp mode or wrong temperature readings.
Did you know: A fault code points to the sensor circuit, not always the sensor itself, so check the connector, wiring and supply voltage before buying.
Fuel injection and delivery
What it is: Parts that deliver fuel to the cylinders in the right amount and at the right pressure: injectors, fuel rails, regulators and high-pressure pumps. On the 2.8 and 3.0 CRD diesels used by Jeep and Chrysler (VM Motori engines) this is a common rail system.
Where it is fitted: On the engine: on the intake manifold or in the cylinder head and along the fuel lines.
Signs of wear: Signs are hard starting, rough running, jerking, smoke, higher fuel consumption, injector knock or a fuel smell.
Did you know: When replacing injectors on a common rail diesel, always use new sealing washers, and new injectors often have to be coded to the engine computer.
Shop — Fuel injection and delivery
Fuel pressure sensors
What it is: The sensor measures fuel pressure in the fuel system and reports it to the engine computer, which uses it to control the pump and injection. It is especially important on common rail diesels and direct-injection gasoline engines.
Where it is fitted: Usually screwed into the fuel rail or the fuel supply line.
Signs of wear: Signs of failure are hard starting, loss of power, the engine going into limp mode and the check engine light.
Did you know: A sensor on a high-pressure rail is replaced with the engine off and the pressure bled down, and the sealing face must be perfectly clean, because any dirt goes straight to the injectors.
Ignition coils
What it is: The coil turns the low voltage of the vehicle's electrical system into the high voltage needed to fire the spark plug. Without a working coil the mixture in the cylinder will not ignite properly.
Where it is fitted: On newer engines it sits directly on the spark plug of each cylinder; on older ones it is a shared pack connected to the plugs by wires.
Signs of wear: Typical signs are misfires, jerking under acceleration, rough idle and a flashing check engine light.
Did you know: If you suspect a coil, swap it with the one from the neighbouring cylinder: if the misfire code moves with it, the coil is at fault, not the plug or injector.
Intake air temperature sensors
What it is: The sensor measures the temperature of the air drawn into the engine. The engine computer uses it to calculate fuel quantity and ignition timing.
Where it is fitted: In the intake duct, air filter box or intake manifold; it is often part of the mass air flow sensor.
Signs of wear: A failure shows up as harder starting, rough running, higher fuel consumption and a sensor fault code stored in the engine computer.
Did you know: Before replacing the sensor, inspect the connector and wiring, because corroded terminals cause the same symptoms as a failed part.
Shop — Intake air temperature sensors
Manifolds
What it is: The intake manifold distributes air or mixture to the individual cylinders, while the exhaust manifold collects exhaust gases from the cylinders and sends them to the exhaust system.
Where it is fitted: Bolted to the cylinder head: the intake on the intake side, the exhaust on the exhaust side.
Signs of wear: Signs include ticking or hissing on a cold engine (exhaust leak), exhaust smell, cracks, and on the intake side, vacuum leaks and rough running.
Did you know: On many American V8s the exhaust manifold bolts break; the typical ticking is loudest right after a cold start.
Oil filters
What it is: The filter traps metal particles, soot and other contaminants circulating in the engine oil. This protects the bearings, camshafts and turbocharger from premature wear.
Where it is fitted: Screwed onto the engine block as a spin-on filter, or fitted as a cartridge inside a filter housing.
Signs of wear: It is replaced at every oil change; a clogged filter can reduce lubrication.
Did you know: Lightly oil the seal of a new spin-on filter before fitting it, and with a cartridge filter also replace the housing cap O-ring.
Oil pans
What it is: The oil pan closes the engine from below and holds the oil that the pump draws into the lubrication system. It has a drain plug for oil changes.
Where it is fitted: Bolted to the bottom of the engine block, at the lowest point of the engine.
Signs of wear: Replace it when it is cracked or dented after an impact, the drain plug thread is stripped, or a leak cannot be fixed.
Did you know: On off-road vehicles the pan is exposed to rock strikes, and fitting a new drain plug washer at every oil change is a good habit.
Oil pressure sensors
What it is: The sensor measures oil pressure in the lubrication system and sends it to the gauge or warning light on the dashboard. It warns the driver when engine lubrication becomes insufficient.
Where it is fitted: Screwed into the engine block or oil filter housing, in an oil passage.
Signs of wear: Replace it when the reading jumps around or stays at zero on a healthy engine, the warning light comes on for no reason, or oil leaks from the sensor.
Did you know: Before replacing the sensor, check the actual pressure with a mechanical gauge, because the light may mean a real loss of pressure, and driving like that quickly ruins the bearings.
Oil pumps
What it is: The pump draws oil from the pan and pushes it under pressure to the bearings, camshafts, lifters and turbocharger. It is the heart of the lubrication system.
Where it is fitted: Inside the engine: at the front of the block behind the timing cover or in the oil pan, driven by the crankshaft.
Signs of wear: A worn pump causes low oil pressure, an oil light that comes on when the engine is hot, and noisy lifters.
Did you know: Prime a new pump with oil before fitting so it picks up oil from the first start, and check the pickup tube and screen at the same time.
Piston rings
What it is: Rings seal the piston in the cylinder: the top rings hold compression and combustion pressure, and the bottom oil control ring scrapes oil off the cylinder wall.
Where it is fitted: In the piston grooves, inside the engine cylinders.
Signs of wear: Worn rings cause higher oil consumption, blue exhaust smoke, low compression and power, and increased blow-by into the crankcase.
Did you know: Check the ring end gap in the bore before fitting, and stagger the gaps of successive rings, never in one line.
Pistons
What it is: The piston moves in the cylinder, takes the combustion pressure and transfers force to the crankshaft through the connecting rod.
Where it is fitted: Inside the cylinders of the engine block, connected to the rod by a wrist pin.
Signs of wear: Replace it when burnt, cracked, scuffed or worn loose, which shows up as knocking, low compression and smoke.
Did you know: Pistons are matched to the bore size after machining, and the direction mark on the piston crown must be observed when fitting.
Pulleys and accessories
What it is: Pulleys, tensioners and idlers form the belt drive that carries crankshaft rotation to the alternator, power steering pump, A/C compressor and often the water pump.
Where it is fitted: At the front of the engine, along the path of the serpentine belt.
Signs of wear: Signs are squealing or whining at the front of the engine, a shaking tensioner, worn or noisy idler bearings and a belt that slips off or cracks.
Did you know: The crankshaft pulley is often a rubber-bonded harmonic balancer; when the rubber separates the pulley wobbles and the belt can come off.
Shop — Pulleys and accessories
Spark plugs
What it is: The spark plug creates the spark that ignites the air-fuel mixture in the cylinder of a gasoline engine.
Where it is fitted: Screwed into the cylinder head, with the electrodes inside the combustion chamber.
Signs of wear: Worn plugs cause misfires, harder starting, jerking and higher fuel consumption; replace them at the service schedule interval.
Did you know: The 5.7 Hemi uses two plugs per cylinder, 16 in total, and in aluminium heads the plugs must be torqued correctly because the thread is easy to damage.
Thermostats
What it is: The thermostat is a valve that keeps the engine at operating temperature: it blocks flow through the radiator when the engine is cold and opens once it warms up.
Where it is fitted: In the thermostat housing on the engine, usually at the coolant outlet or inlet.
Signs of wear: A thermostat stuck open makes warm-up slow and cabin heat weak, while one stuck closed leads to overheating.
Did you know: Fit a thermostat with the opening temperature specified for the engine, because a colder one hurts fuel economy and can set a temperature fault code.
Throttle position sensors
What it is: The sensor tells the engine computer how far the throttle is open, i.e. how much air the driver is asking for with the pedal. The computer uses it to set the fuel quantity and, on automatics, the shift points.
Where it is fitted: On the throttle body, at the throttle shaft; on electronic throttle bodies it is often built into the housing.
Signs of wear: Signs are jerking, hunting idle, delayed throttle response, poor shifting on an automatic and the check engine light.
Did you know: After replacing the sensor or cleaning the throttle body, a throttle relearn is often needed, otherwise the idle may be unstable.
Shop — Throttle position sensors
Timing components
What it is: The timing system keeps the crankshaft and camshafts in sync so the valves open at the right moment. A set includes the chain or belt, sprockets, tensioners and guides.
Where it is fitted: At the front of the engine, behind the timing cover.
Signs of wear: A stretched chain rattles after a cold start and triggers cam/crank correlation codes; a belt is replaced by the mileage or age set by the manufacturer.
Did you know: When replacing the timing, renew the tensioners, guides and rails at the same time, and with a belt usually the timing-driven water pump too, since the labour is the same.
Valve lifters
What it is: Lifters transfer motion from the camshaft lobes to the valves or pushrods. Hydraulic versions take up valve clearance automatically.
Where it is fitted: In the engine block (cam-in-block engines such as V8s) or in the cylinder head under the camshaft.
Signs of wear: Wear shows up as ticking or clattering from the top of the engine, misfires and cylinder fault codes.
Did you know: On V8s with cylinder deactivation (MDS on the Hemi, AFM/DFM on GM) lifter failure is a known issue, and the camshaft is usually inspected or replaced along with them.
Valves and cylinder head parts
What it is: Intake valves let air or mixture into the cylinder and exhaust valves let the burnt gases out. This group also includes guides, seats, springs and valve stem seals.
Where it is fitted: In the cylinder head, above the combustion chambers.
Signs of wear: Worn stem seals cause blue smoke after starting and oil consumption, while a burnt or leaking valve causes low compression and misfires.
Did you know: Replace the valve stem seals every time the head is dismantled, and lap new or machined valves into their seats.
Shop — Valves and cylinder head parts
Water pumps
What it is: The pump circulates coolant between the engine, radiator and heater core. Without it the engine overheats quickly.
Where it is fitted: At the front of the engine, driven by the accessory belt or, on some engines, by the timing chain or belt.
Signs of wear: Signs are coolant leaking from the weep hole, a loose or noisy bearing, coolant loss and overheating.
Did you know: On some V6 engines the pump sits behind the timing cover and is chain driven, so a leak can end up in the oil; such a pump is best replaced during timing work.
Where to next
- Catalogue: engine — choose your make, model and generation.
- Parts by VIN — we will check the fit for your car.
- Parts guide — other systems.
We sell aftermarket replacement parts, not genuine parts from vehicle manufacturers. Descriptions are general — check the fit for your vehicle by OEM number or VIN.