I've just posted this on the ur-quattro forum, but many people seem to prefer this place, so for completeness ...
So far this seems to be an MB-only issue, but it could affect MC-1 and 1B engines in Audi 100TQ and 200TQ cars. I haven't seen it on any 20Vs yet.
There are lifters available on the bottom-feeder market that are too short to work properly in an MB. I've seen two cases now of these unbranded lifters supplied by generic head repair companies. Careful depth gauging suggests the lifter is almost 0.75mm too short.
The result is an immediate non-cyclic tap on starting - almost a hammering. On one engine, it was recognised quickly and eventually diagnosed. It's not the sort of problem you expect.
On the second one, the car was driven and the cam shows bearing face damage on #2 and #3 bearings, with traces of damage on #1.
The easiest defining feature is the oil feed hole on the side of the lifter. Genuine Audi lifters (made by INA and marked as such underneath) have a small round hole entirely within the oil feed groove around the lifter.
The problematic ones have no maker's mark and the oil feed hole is shield-shaped, cut away below the groove.
So far this seems to be an MB-only issue, but it could affect MC-1 and 1B engines in Audi 100TQ and 200TQ cars. I haven't seen it on any 20Vs yet.
There are lifters available on the bottom-feeder market that are too short to work properly in an MB. I've seen two cases now of these unbranded lifters supplied by generic head repair companies. Careful depth gauging suggests the lifter is almost 0.75mm too short.
The result is an immediate non-cyclic tap on starting - almost a hammering. On one engine, it was recognised quickly and eventually diagnosed. It's not the sort of problem you expect.
On the second one, the car was driven and the cam shows bearing face damage on #2 and #3 bearings, with traces of damage on #1.
The easiest defining feature is the oil feed hole on the side of the lifter. Genuine Audi lifters (made by INA and marked as such underneath) have a small round hole entirely within the oil feed groove around the lifter.
The problematic ones have no maker's mark and the oil feed hole is shield-shaped, cut away below the groove.
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