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      06-18-2011, 06:14 PM   #1
mattsfeir
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Drives: 335xi
Join Date: Oct 2009
Location: CO

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vacuum line fix - low boost, underboost, 30ff, wastegate rattle

Here's a quick vacuum line fix that solved a lot of problems for me. My car's boost kept getting lower and lower, ultimately ended up around 3psi when it should have been 13.5psi. I made a boost leak tester which showed me one boost leak, but even when that was fixed, the boost level didn't change. I was getting the 30FF error code under full throttle and the wastegates really started rattling, sounded like diesel clatter.

Robert at Vishnu spent some time on the phone diagnosing the issue and said I should check all the vacuum lines, especially the ones right by the oil filter (red arrow in pic below). He also mentioned that right after shutting the car off, immediately disconnect the vacuum connector (blue arrow in pick below) and I should hear a whoosh of air being sucked in due to the vacuum. They had this same issue with a beta tester's car.

One of my vacuum lines had split right behind the oil filter, found the leak by disconnecting the vacuum connector and blowing air into it with my mouth. While that may sound weird, it was very easy to find the leak. Replaced both of the original vacuum lines with the 5/32 line from Pep Boys and all was fixed. There was vacuum when I shut the car off and boost is now back to normal.

My car is an 07 with 54k miles, as more of these cars get older and the heat from the oil filter takes it toll on the rubber lines, I'd guess more people will have this issue.

I had an appt scheduled with the dealer the next day to diagnose this, not sure what they would have charged, but I'd guess $100-$200 and the line cost $5 at Pep Boys. Great service from Vishnu giving me tips on fixing a hardware issue, Procede had nothing to do with this.

Edit: Probably best to cut the old vacuum lines off as they may be brittle and stuck to the plastic connectors. I used a utility knife to slice the ends of the old vacuum lines open (parallel to the line), then they're easy to peel off the plastic connectors. Also note that you could have a vacuum leak somewhere else besides this spot, this just appears to be a common spot.
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Last edited by mattsfeir; 06-19-2011 at 08:13 PM..
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