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Thread: Idle

  1. #1
    Join Date
    Aug 2005
    Posts
    593

    Default Idle

    At idle I can hear the sh-sh-sh sound from the engine. It is not very pronounced, but you can hear it if you lean over the engine. Is it the way it should be or air is being sucked in?
    I tried spraying carb cleaner around vacum lines, did not get any rev increase. Used Hi-Gear carb cleaner:
    http://www.higearproducts.net/en/prod_fs.htm
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  2. #2
    Join Date
    Jan 2006
    Location
    Brisbane, Queensland.
    Posts
    145

    Default

    t_marat,

    It could possibly be a leak from the exhaust manifold gasket (Against the head) or it could be from the flange gasket (Bottom of the exhaust manifold there is a joint to the rest of the exhaust or engine pipe), it will get louder if you drive it and load it up, that is if you try driving up a longish hill in a higher gear than you would normally use the sound will definately get louder.

    Just a thought to check at least.

    Boom n Zoom

  3. #3
    Join Date
    Aug 2005
    Posts
    593

    Default

    I changed the gasket on the rear of the gearbox, and at that time the mechanic checked for any leaks at the exhaust manifold. Could not find any. He said any leak would make itself visible by turning to black the nearest surrounding area. He did check also with his hands for any leakage (while engine is running).
    He said that the sound is likely from the ICV valve.
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  4. #4
    Join Date
    Oct 2005
    Location
    Houston, TX (USA)
    Posts
    181

    Default I had same sound t idle......

    it turned out to be Non-Return valve of brake booster. Neepal was broken and air was being sucked from the tiny hole. I sealed theat home and it fixed that problem.

    Hope that will help.

    Good luck
    Akhil

  5. #5
    Join Date
    Aug 2005
    Posts
    593

    Default

    Quote Originally Posted by Akhil
    it turned out to be Non-Return valve of brake booster. Neepal was broken and air was being sucked from the tiny hole. I sealed theat home and it fixed that problem.

    Hope that will help.

    Good luck
    Akhil
    Does that leak affect idle quality? any roughness?
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  6. #6
    Join Date
    Oct 2005
    Location
    Houston, TX (USA)
    Posts
    181

    Default Mine didn't affect much, but

    idle and gas milage got better after fixing that leak. I also pleace vaccum hose, rubber seal at booster and all the clamp at some time. You might wanna check whole vaccume route from intake to booster including non-return valve.

    Akhil

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