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Old 10-13-2012, 01:47 PM
Supercourse Supercourse is offline
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Location: British Columbia, Canada
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Mein Auto: 2004 X3 2.5i
Originally Posted by thompsonmd View Post
I also checked the vacuum on the oil cap, it was strong. I was impressed. I didn't know there would be any suction there.
I'm not an expert on this oil filler cap removal test, so someone else can chime in, but as I understand it:

1 of 3 things can be observed.

1. air blowing out which indicates a failed CCV

2. nominal suction which indicates everything working normally

3. strong suction which indicates a blockage somewhere in the CCV system but the valve itself still working

In addition, the revs should drop a bit as you are introducing a vacuum leak, and if it stumbles it should recover itself.

If you already have a vacuum leak, I suppose that either any further drop in revs might not be noticeable, or it will to the extent that it stalls.
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