M54B25 / M54B30
The last of the old-school BMW sixes and the one before direct injection arrived. It's smooth, tough and cheap to keep, and what it does instead of failing is leak: the valve cover, the oil filter housing and the cooling system are all wear items by now.
| Configuration | I6, naturally aspirated | Displacement | 2979 cc |
| Fuel | petrol | Injection | port |
| Shared components | oil filter housing | ||
Cars using this engine
Engine and component issues
Temperature creeping above the middle of the gauge, a sweet smell after a run, or coolant pooling under the front of the car. The plastic expansion tank, the thermostat housing and the water pump are wear items with a service life rather than lifetime parts. Most cars of this age are on their second set, and an overheat on this engine can warp the head.
Check: Look for a stained expansion tank and crusty residue around the hoses, watch the gauge on a longer drive, and treat any history without cooling work as meaning it's due.
Oil pooling on the subframe, oil on the serpentine belt, drips on the driveway. The gasket between the filter housing and the block fails. Oil then lands on the belt, and a belt that shreds can be drawn into the front crank seal.
Check: Put the car on a lift. Check the belt itself for oil contamination. An oily belt is the version of this fault that ends badly.
A rattle from the intake manifold, a flat spot in the mid-range, and sometimes a fault code for the intake system. The DISA unit's pivot and flap wear, and in the worst case parts of it can come loose and be drawn into the engine. It's a known age item rather than a design flaw.
Check: Listen at the intake manifold with the engine idling and warm, and scan for intake-system codes.
Chassis, gearbox and body issues aren't listed here. They depend on which car the engine is fitted to. Open a variant page for the merged list.