<_< I have a Audi 100 . 2,3E Avant 1992.. Heard a ticking noise from the engine.
Service told me it was the valves hydraulic lifters needing repairs. Many $$$$.
I kept driving and finally narrowd the problem to the vacuum pump. Took out the steel bar that drives it, and surprise, the ticking noise disappeared and no other problem occured. What is it good for, the vacuum pump ???