I think the idea behind the CCV is to keep the recycled gases as inert as possible to reduce NOS emmisions similar to how an EGR works. Sucks for moisture though! ;( even a small amount of atmospere let in would allow the whole thing to work a lot better. I imagine the engineers where given zero tolerance though.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)