The successor to the M54, used across the E90 3 Series and E60 5 Series — mechanically strong, with reliability concerns concentrated in a handful of electrical and cooling components rather than the engine's core.
BMW moved to an electric water pump and thermostat on this generation, which improved efficiency but introduced a new failure point that the previous plastic-parts issue on the M54 never had: an electronic component that can fail outright rather than degrade gradually. The magnesium/aluminium composite block has its own minor concerns around bolt corrosion on very high-mileage, poorly maintained examples, but this is a less common complaint than the cooling system.
Not a guarantee, but a pattern seen consistently across owner forums and independent-garage reporting.
First electric water pump failures, often with little warning beyond a temperature gauge spike.
VANOS solenoid wear becomes more common, causing rough idle or minor power loss.
Core engine internals remain sound on documented, well-maintained examples.
Ask whether the electric water pump has ever been replaced — if not, and mileage is past 100,000km, factor a preventative replacement into your offer.
Watch the temperature gauge closely during the test drive for any unusual fluctuation, an early sign of cooling system trouble.
Listen for rough idle or hesitation that could point to VANOS solenoid wear, inexpensive to fix but worth noting.
Model-specific pages, with notes on how it behaves in that particular car.