Engine internals

Cylinder head

Closes the cylinders and carries the valves that control breathing.

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

Bolted above the engine block.

How it works

Ports admit air and release exhaust while valve seats, guides and coolant passages manage sealing and heat.

Think of it as

A busy roof with carefully timed doors.

Symptoms when it fails

Overheating, coolant loss or low compression can involve the head, gasket or other components.

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

A BMW cylinder head is matched to its engine’s valve gear, injection system and cooling layout.

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-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.Connecting-rod bearingLets a connecting rod rotate around its crankshaft journal.