The copper washer under the injectors of the five cylinder PD diesel (Transporter T5, Crafter I) gets crushed over time, and the seal lets go. First you hear a hissing, "coughing" noise from the engine bay when cold, then soot builds up around the injector. If it is not replaced at this point, the escaping combustion gas erodes the injector seat in the cylinder head: from then on comes cylinder head machining or replacement, far more expensive than the copper washer. The AXD is the earliest and weakest version of the family; the later BNZ/BPC is structurally strengthened. What accelerates it is almost always oil that does not meet the specification.

The internal springs of the flywheel tire, and the two discs knock against each other. The signs are a rattling or knocking from the bellhousing at idle and when releasing the clutch pedal, and vibration through the floor. If the clutch slips without a burnt smell, that also points to the flywheel. It is worth replacing in time: a disintegrated flywheel can destroy the bellhousing too. At a clutch replacement the two go together anyway.

The vanes of the variable geometry turbo are glued together by soot and oil arriving through the EGR. First you get overboost or a lack of boost, then loss of power above 2,000 rpm, and finally limp mode. Caught in time it is enough to remove the turbo, clean it and fit a new actuator rod. Short urban trips and gentle, low rev driving speed up the deposits.

The G62 sensor tells the engine control unit how hot the coolant is. If it is faulty, the control unit thinks a warm engine is cold, and runs it rich: hard warm or cold starting, a rough idle, markedly increased fuel consumption, and a dash temperature gauge that jumps around or never reaches its usual reading. The part is cheap and can be replaced in half an hour: the trouble is that many people do not recognise it and replace an injector or a lambda sensor instead. If the fault persists, the rich mixture can destroy the catalytic converter too.