Hmmm, this might be a question better suited for a specialist on VM Motori engines - DCJ FSM for this beast is, well... let's just say I've seen better in my day. Besides the fact that my CD version of the FSM doesn't want to work any more.

Could be there's some type of crankcase/valve cover pressure relief on the passenger side of the engine. On my '87 MB, back at the rear passenger side of the valve cover, there's a small port between 1/16" and 1/8" in diameter - according to the MB FSM, it's a "pressure equalization port", apparently with some sort of relief/check valve arrangement inside the valve cover.

On my wrecked '87, when I tried adding a water bubbler jar downstream of the Provent, it apparently created just enough backpressure that oil started leaking out of this port and running down the side of the valve cover.

We might have a similar provision that VM Motori designed into our engine, but DCJ didn't bother mentioning in the FSM because they felt it would never need servicing and/or it wasn't worth the time to teach their techs about (as if they bothered teaching them much of anything to begin with).

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Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler