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      11-21-2015, 03:06 PM   #15
vespa
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Drives: 2011 335i
Join Date: Dec 2014
Location: Thousand Oaks

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Update: 3 months after replacing the front main seal, the rear main blew, sounding exactly like this:



It turns out that the seals aren't actually "blowing", they're just sucking -- literally sucking in air and whistling like a party balloon. In my case this was the result of a failed PCV valve allowing excess crankcase vacuum. I replaced the PCV valve, not the rear main seal, and all is well now.

Detailed PCV valve info here: http://www.e90post.com/forums/showthread.php?p=18947012
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