RF7J 2.0 MZR-CD

Carbon and tar building around the injectors, a chuffing noise at idle, a rising oil level and a diesel smell to the oil. The injector seats leak combustion gases into the head and, in turn, contaminate the engine oil. Combined with poor particulate-filter regeneration behaviour, that slowly damages everything the oil is supposed to protect. Mazda replaced this engine with the 2.2 partway through the generation.

Check: Look for black tarry deposits around the injectors, check the oil level and smell it, and treat any unexplained rise as this fault until proven otherwise.

Later parts: Replaced by the 2.2 MZR-CD during the generation

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.