CHECK THE HEAD GASKET

The big V8 is fundamentally strong but look for an iron-clad service history from a main dealer or reputable specialist. The big worry is cylinder head gasket failure – changing the pair will result in a £5000 bill – so ensure that the cooling system is in tip-top condition. Post-1994 cars are more likely to suffer from problems, but coolant loss at speed will rapidly lead to failure. The alloy construction means antifreeze levels are crucial in preventing corrosion. Piston-knock probably points to previous overheating.

The main issue with the 6.75-litre V8 (which has only just gone out of service) is cylinder head gasket failure.