There is no electric or mechanical valve that allows crankcase ventilation. IT is done through two hoses on the valve covers. One per valve cover. One hose connects to the air cleaner housing and the other, as Doc explained, is under vacuum at idle and has a hole in it for this reason.

I would check those hoses, I would think that one or both of them has collapsed. I have seen this on later v-8's/

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS