Engine internals

Connecting-rod bearing

Lets a connecting rod rotate around its crankshaft journal.

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

Inside the big end of each connecting rod.

How it works

Bearing shells support cyclic combustion loads using an oil film supplied through the crankshaft.

Think of it as

A lubricated sleeve inside a moving hinge.

Symptoms when it fails

A loaded knock or metallic debris can suggest wear but does not identify the bearing by itself.

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 M engine discussions focus on rod bearings; maintenance advice must identify the actual engine and evidence.

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.