Engine internals

Intake valve

Opens a passage for fresh air into a cylinder.

Drag to turn it Open in the 3D lab
Where it sits

In the cylinder head at each intake port.

How it works

The valve seals against its seat when shut and opens according to the cam and valve-control mechanism.

Think of it as

The entrance door to the combustion room.

Symptoms when it fails

Poor sealing or deposits can cause rough running or reduced airflow; testing is needed.

Lifespan

Usually condition-based rather than a routine replacement. Lubrication, overheating and the exact engine affect wear.

Repair cost

Internal-engine work is usually labor-intensive. Diagnosis and the engine code determine the repair scope.

The BMW angle

Some BMW direct-injection intake valves are not washed by fuel in the way port-injected valves are.

Used in

BMW petrol and diesel engines; petrol-only systems are identified individually.

Sources
Same system

Engine internals

Engine blockHolds the cylinders and supports the engine’s rotating parts.Cylinder headCloses the cylinders and carries the valves that control breathing.Cylinder-head gasketSeals combustion pressure, oil and coolant between the block and head.PistonReceives combustion force and moves up and down inside a cylinder.Piston ringsSeal combustion gas and control the oil film on cylinder walls.Connecting rodTransfers piston force to the crankshaft.CrankshaftTurns the pistons’ back-and-forth motion into rotation.Crankshaft main bearingSupports the crankshaft on a controlled film of oil.