OM642 3.0 V6 CDI

Oil weeping down the back of the block, burning smell, oil in the valley beneath the intake. The oil cooler sits in the vee under the intake manifold and its seals harden with age. Access requires the intake off, so labour dominates the bill.

Check: Look down the back of the engine with a torch for wet oil and fresh cleaning. A suspiciously spotless engine bay on a 200,000 km V6 deserves a question.

Warning light, limp mode, oil level rising above the maximum mark from fuel dilution. The filter needs sustained hot running to regenerate. A car used for short urban trips never completes a regeneration cycle.

Check: Read the DPF soot load and the distance since the last regeneration on a scan tool, and check the engine oil level and smell it for diesel. Ask what the car was used for. A short-trip city diesel is the wrong car regardless of mileage.

Coolant loss with no visible external leak, white smoke, sweet smell. The EGR cooler cracks internally and leaks coolant into the intake. BMW recalled affected diesels over a fire risk from glycol deposits igniting.

Check: Check coolant level and look for unexplained top-ups in the service history. Verify the recall was carried out. It's free and searchable by VIN.

Limp mode and power loss, usually with fault code P2015 stored. The actuator motor that drives the intake-port shut-off flaps in the manifold fails, frequently after being shorted by oil dripping from the turbo-inlet seal above it; the flaps or linkage can also seize.

Check: Scan for P2015 and related intake codes; a car that has thrown it before is likely to again unless the oil-leak cause was addressed.