Re: Knocking and oil residue

["Bruce Bell" <bbell@csn.net>]

Other suggestions are reasonable; but one possibility for the knocking (
assuming you have the 5cyl.) is the vacuum pump attached to the head (near
the upper radiator hose manifold). this generates a fairly loud knocking
that has a rather hollow sound. I thought connecting rods when I first heard
it. Lifters will be higher pitched  and more of a chatter.

the Vacuum. pump has a steel rod that is actuated by a camshaft eccentric.
When it gets dirty it tends to stick then release with impact against the
cam. Solution? Try a can of engine cleaner in the oil at idle for about
10-15 min then replace the oil and filter. don't rev the engine with the
cleaner. It does not have great lubricating properties. You may have to do
this over a couple of oil changes. Audi's like clean oil.