Chrysler A630 (3.0 V6 diesel)

VM Motori's 3.0-litre V6 diesel — sold as the EcoDiesel by Jeep and Ram and as the 3.0 CRD by Chrysler, Lancia and Maserati, in the 300, Thema, Ghibli, Levante and Quattroporte.

Its emissions equipment is the dominant source of complaints and the reason its history matters. The engine was covered by an emissions settlement in the United States, and affected vehicles received revised calibration and hardware — so the first question about any example is which software it is running, since the recalibrated cars behave differently and some owners report the change.

The EGR cooler is the specific failure worth naming. It cracks, coolant enters the exhaust stream, and the car produces white smoke and loses coolant with no external leak. Coolant disappearing from a 3.0 CRD with a clean engine bay is this before it is a head gasket, and the diagnosis is the opposite way round from most engines.

Beyond it, the recurring items are the diesel particulate filter on short-journey cars and, at higher mileage, main bearing wear, which announces itself as a low-frequency knock under load and is not a repair anybody undertakes lightly on a V6 in a transverse or tightly packaged bay. Oil grade and interval are not routine advice here.