chassis

Vacuum in the crankcase comes from the fresh air inlet side of the PCV system. There are generally dedicated tubes from downstream of intake manifold, into the crankcase, for this.

OVS devices are on the "exhaust" side of the PCV system, taking air and fumes out of the crankcase, through the OVS where oil liquid is deposited and returned to the sump, and passing the "treated" air into the intake system to be combusted.

If the OVS leg is plugged because of OVS failure, and there is too much vacuum causing the RMS to get sucked inward, it means that the fresh air leg of the PCV system has insufficient flow capacity to avoid excessive vacuum.

OTOH if the PCV fresh air leg does have enough capacity to avoid excess vacuum, and the OVS leg is plugged, high crankcase pressure would result, pushing the RMS out.

Does anyone have a clear diagram of the entire PCV system for M17x? Showing both fresh air and OVS legs?

chassis

I was looking at M17x engines on eBay. There are differences in the E63 OVS design compared with W205 C63 and W222 S560.

RMS failure seems to be concentrated on E63 and G63, but I do believe C63 has some RMS failures reported on this site. Part of the explanation could be a bad system design (likely, it's MB after all) and the nuances of the G63 and E63 installation may be "worse" than W222 and W205, causing a higher failure rate for W463 and W213. Just a guess.

I haven't found the PCV fresh air inlet tubes for the PCV for M17x, either in photos or diagrams. If someone could post them it would be helpful and appreciated.

p.s. the M17x 4.0TTV8 has many similarities, or nearly identical characteristics, compared with the VAG EA825 4.0TTV8. The EA825 has had an OVS failure reported on rennlist, but it is rare, and it doesn't cause RMS failure (so far).