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  1. #1
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    Vacuum Leak help

    Long time listener, first time caller.

    Car: 2003 525iT with 68k miles, purchased 3/2010

    I recently completed the Beisan Systems double-vanos seal procedure. As part of the process, I ended up replacing my radiator. Very good product and procedure and I can definitely tell a difference on cold starts and gave me a little more oomph.

    About two starts after the install, the engine stumbled briefly and subsequently threw two codes: p0171 and p0174 both banks lean. Note: temp was about 39 degs F and seems to be more of an issue. I've since monitored STFT and seen it as high as 20% on 1st and 2nd sensor so I think I have a vacuum leak and not a o2 sensor issue. O2 sensor is original though.

    Have cleaned the MAF but code came back.

    Both intake boots are on order and I'm considering CVV but it seems early for the CVV and hoses to leak!? Car doesn't smoke and I can't seem to find a leak by listening to bay.

    Wanted to poll folks who have had similar problems. Interest to learn what ultimately fixed the P0171 and P0174 (or similar lean issues).

    Thanks in advance.





  2. #2
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    Member No: 56726 lezonebay is an unknown quantity at this point lezonebay's Avatar
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    my bet is temperature sensor

    are you sure everything is plugged back ? check the plugs, vacuum hoses, sensor connectors AGAIN.

    Since it started after the repair, it is most likely connected to the repair.

    valve cover area and front radiator area should be checked, every connector and vacuum junction re-checked. I suspect a forgotten something there. Too much coincidence !!!

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  3. #3
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    100% with you but can't find anything. Looking...


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    Re: 100% with you but can't find anything. Looking...

    In our '02 E46 with the same engine, it was both intake boots (which you have on order) and also the check valve at the brake servo. After it has been parked for a while, do you still have vacuum assist in the brakes before you start the engine, or is a hard, high pedal?
    '03 525i Sapphire Blu/Grey, SP, Nav
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    If it's not CVV.......

    next common issue on M54 engines is vacuum leak at DISA valve. 30 minutes and a tube of form-a-gasket will fix. This fixed these codes on my '01 530i.

    http://forum.e 4 6 fanatics.com/showpost.php?p=8984776&postcount=51
    remove spaces in link

    Paul S
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  6. #6
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    Re: If it's not CVV.......

    Thanks for the feedback. I took the DISA off a couple of days ago. I thought the gasket looked ok and the DISA performed as it should. How did you know gasket was bad?

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    Think I found it

    Started CVV replacement job today, hoping to only have to replace intake boots. I removed intake boots and found no holes, splits, etc. After removing the intake boots and DISA, using a flashlight, I could see most of the CVV hoses. I found a small split in the CVV hose leading to the dipstick tube.

    Planning to complete CVV replacement job over next few days. Purchased cold weather CVV kit from Bavarian Auto. Any tips appreciated.


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    Installed CCV + 4 hoses and...

    it's been 3 days without the SES light. The CVV hose leading to the dipstick was literally in shreds.

    Thank you for all of the feedback and ideas. Hoping that I solved it.

  9. #9
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    Re: 100% with you but can't find anything. Looking...

    JKRIT - Replacing the CVV + hoses fix my P0171 and P0174 lean codes. However, I still think I have a vacuum leak. If I hold a steady throttle at around 1500 RPM, RPMs will fluctuate (down to 1,000 then up to 2,000--maybe exaggerated but still there) like the computer is trying to compensate for a lean condition.

    Per your question, I checked my brake pedal and sure enough it is hard and high first thing in the morning. Once I start the car, vacuum assist returns. I took off the cabin filter housing this morning looking for a leak but couldn't find valve, hose, etc. Can you point me in the right direction? Do you know if it is the same between e46 and e39? I saw some pics last night of an e46 than made me think it was different.

    Thanks.

  10. #10
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    Found check valve using Bentley

    JKRIT - To be clear, it was the check valve that went bad and not the hose on your e46?

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