E46 M3 Vanos pump wear inspection

[ac427]

How can a vanos pump unit that is removed from the engine be inspected for Vanos pump wear, are there clearances to be measured?

I have a spare vanos unit an want to overhaul it with the Beisan kits i have but i obviously don't want to do this if the pump is worn.

[911Fiddler]

All that can easily be done is to pop a mic on the pump pistons. I’m told however that the main wear point is the pump spindle and the corresponding disk bore, both of which are more than hard to measure. Special kit required.
Off the car: inspect visually for signs if wear.
on the car: pressure test and leak down measurement, see how it compares to others (benchmark).