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In Reply to: Back of intake manifold: What is it? posted by Jerry on December 31, 2001 at 19:42:14:
Happy New Year. BMW calls the thing behind the intake manifold a “cover with non-return valve”; those Germans are pretty creative. Your are correct, it is part of the crankcase ventilation system. It ultimately connects to an “oil separator” by way of a “vent pipe” and several “connectors” and O-rings along the way. The “oil separator” connects to the “oil pipe outlet.” I used quotation marks to designate official BMW Parts Catalog nomenclature. I didn’t want you to think I was making any of this up, I’m not that creative.
Apparently what this system does is scavenge oil-laden air from the intake manifold and drain it back to the block. I have never removed this item myself but it appears there is a valve (PCV valve?) in the “cover with non-return valve” which allows the engine to pull oil-laden air through it by way of the crankcase vacuum. Similar (sort of) to what you find on most cars with a PCV valve. In this case the engine vacuum draws air from the intake manifold, through the “cover with non-return valve” via connecting pipes to the “oil separator” which allows oil free air to return to the intake manifold and the oil to drain back to the crank case. It’s a pretty elaborate system. Given its mission, I think you can appreciate why it was so dirty.
I would be happy to send you assembly digrams and the parts breakdown for this system. If you would like this information E-mail off line and I will send them to you.
REGARDS,
Ron Brown
Got a 1994 740 M60 V8. Saw this "thing" bolted to the back of the intake manifold with 7 #30 torx bolts (suspect some variation of PCV - got to remove coolant resivoir to get to it).
The reason for all of this is a "sometimes" crappy idle.
Took that "thing" off & cleaned the heck out of it. It was dirty as sin. Also saw a small pool of oil in the intake manifold where the thing came from. That area also dirty as sin. Cleaned all, replaced all (no new - replaced what was there, cleaned).
At the very bottom of this "plate thing" is an air port. It appears to vent (out) rather than vacuume (in).
Covered it with duct tape & engine blew oil from the oil cap & dip stick. Burnt like heck. Folks at the store thought I was on fire!
Removed tape on this unknown port & engine seems to run OK, at least in the garage under no load but various RPM's from 1K to 5K. Not much smoke (maybe left over from before) and idles OK.
Question: What is that thing bolted on the back of the M60 intake manifold and what does it do & how can it affect idle quality?
I'm lost! What the heck is this thing/system???
Thanks in advance!
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