R2AA 2.2 MZR-CD

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.

A rattle at cold start from the front of the engine, and separately a rough idle or uneven running as injectors wear. The timing chain stretches with age and mileage, and the injectors wear in the way most common-rail diesels of this era do. Neither is universal, and both are well enough recorded that a car with no history should be assumed to need attention.

Check: Listen at a genuinely cold start for chain rattle, then scan for injector correction values and per-cylinder contribution.

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.