Engine internals

Valve spring

Returns a valve toward its closed position.

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

Around the valve stem above the cylinder head.

How it works

Spring force keeps valve motion following the intended cam profile while allowing repeated opening.

Think of it as

A spring-loaded door closer.

Symptoms when it fails

Abnormal valve motion, misfires or mechanical noise need inspection rather than spring replacement by guess.

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 valve spring must suit the specific cam and valve assembly, including its intended operating range.

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.