The accessory pulley of the crankshaft is also a vibration damper: there is a layer of rubber between the outer and the inner part. This rubber ages and separates between 100 000 and 150 000 kilometres, and from then on the pulley no longer does its job.

The symptom is vibration at idle, felt through the steering wheel and the instruments, and with it a squeal from the auxiliary belt. The pulley can also be checked by hand: bulging rubber and an outer ring that wobbles when pressed give it away.

At replacement what matters is what goes in its place. A pulley of factory quality with a proper damper is needed; the solid variant without damping is not suitable for this engine.

Another question belongs here, because it concerns the same bolt. At a timing belt change the crankshaft bolt has to be replaced with a new one according to the factory procedure, and tightened in two stages, to 40 newton metres and then a further 90 degrees, with the crankshaft locked. With the belt off the crankshaft must not be turned, because the pistons damage the valves. If the belt change was not done this way, the damage is inside the engine.