on idle.
On a Vectra B. In case it helps.
At first I thought it was a loose heat shield, it's that kinda rattle (listening from, inside the car) but it sounds like it's coming from the timing cover.
But if I turn the steering wheel a tad it stops, and it's not rattling apart from on idle.
Not checked power steering fluid yet (it was dark and I couldn't find the reservoir) and I'm really hoping that the most likely cause isn't the imminent self destruction of chain(s) or tensioner(s).
Enough info to make some suggestions as to a cause/solution?