Wear of the rod bearings is known on this engine, and preventive bearing replacement is established maintenance. The clearance between the bearing and the crankshaft is tight from the factory. With cold, thick oil the lubrication is therefore not enough for the high revs the engine can reach, and revving it hard while cold or using oil outside the specification wears the bearing sooner. The debris appears as metal particles in the oil and in the oil filter, and travels through the whole engine from there. Owners replace the bearing shells between 80,000 and 130,000 km, depending on how hard the car is used. It has led to total engine failure on fewer than one per cent of the S65 engines sold, while the early wear is far more common. In the United States a class action was filed over the 2008 to 2013 M3, and it names the connecting rod and main bearings, the connecting rod side clearance and insufficient lubrication. One more fact belongs to the consequence. On this engine the hydraulic power steering is driven directly by the rotating assembly, so if the engine stops the power steering and the brake assistance go with it.
What to check
- Listen to the engine warm and under load: a deep knocking means a bearing fault
- At idle and at low revs listen for a clacking, knocking noise
- Look at the oil and the oil filter: a metallic glitter is debris
