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Thread: What is this part? Check valve?

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  1. #1
    Join Date
    Dec 2006
    Location
    San Jose, CA
    Posts
    113

    Default What is this part? Check valve?

    Not sure what this is. I think it's some kind check valve, PVC? Should it be cleaned? How do I know if it's bad / working properly? I see a vacuum lead here, closed off. Any one know what the vacuum should read at this location so I can check mine against a know good value?

    Thanks

    sc
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    scott 4991
    535i, 172K miles

  2. #2
    Join Date
    Oct 2004
    Location
    Honolulu
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    3,105

    Default I think this is the booster

    line for the brakes.

    the brake booster uses vacuum to power the power grakes


    Vee ave vays of dealing vid your kind...........

  3. #3
    Join Date
    Oct 2005
    Posts
    518

    Default

    That is in fact a check valve. It allows for the vacuum from the intake manifold to operate the brake booster. It's purpose is to prevent vacuum fluctuation in the manifold due to you applying the brakes. The extra nipple is a known vacuum leak source and thus shouldn't be disturbed. HTH

  4. #4
    Join Date
    Jan 2004
    Posts
    4,150

    Default Uh, not quite, its purpose is to

    allow vacum to be stored in the booster so you have some assist for a stop or two if the engine stalls while driving, If the check valve is working correctly you can push the brake pedal down a couple of times with the engine off and you can feel the boost go away as you use up the stored vacum. The pedal gets harder and higher.


    Quote Originally Posted by Rus
    That is in fact a check valve. It allows for the vacuum from the intake manifold to operate the brake booster. It's purpose is to prevent vacuum fluctuation in the manifold due to you applying the brakes. The extra nipple is a known vacuum leak source and thus shouldn't be disturbed. HTH


  5. #5
    Join Date
    Oct 2005
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    518

    Default

    Quote Originally Posted by Bill R.
    allow vacum to be stored in the booster so you have some assist for a stop or two if the engine stalls while driving, If the check valve is working correctly you can push the brake pedal down a couple of times with the engine off and you can feel the boost go away as you use up the stored vacum. The pedal gets harder and higher.
    I stand corrected

  6. #6
    Join Date
    Dec 2006
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    San Jose, CA
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    Default

    Thanks guys.

    sc
    scott 4991
    535i, 172K miles

  7. #7
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    Feb 2005
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    kIWI LAND(New Zealand)
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    Default

    Thanks I always wondered what that thing was
    89 535 272,000km auto Euro

  8. #8
    Join Date
    May 2004
    Posts
    485

    Default

    Quote Originally Posted by scott 4991
    Not sure what this is. I think it's some kind check valve, PVC? Should it be cleaned? How do I know if it's bad / working properly? I see a vacuum lead here, closed off. Any one know what the vacuum should read at this location so I can check mine against a know good value?

    Thanks

    sc
    PCV, methinks. Those factory clamps suck, and allow vacuum leaks. Better to replace and/or wrap some electrical tape over this and other potential leaks.

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