CLHA 1.6 TDI

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 disappearing with no puddle underneath, a crusty residue around the front of the engine, and eventually a low-coolant warning. The water pump and thermostat housing on this engine family are a plastic assembly that weeps as it ages. It's a wear item rather than a defect, and because the pump is driven off the timing belt on the diesels the labour is more than the part suggests.

Check: Look for dried coolant staining around the front of the engine and check the expansion tank level against its marks. Ask whether it has been done, because most cars of this age have either had it or are due.

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.