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  1. #1
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    Member No: 13147 tomcat is an unknown quantity at this point tomcat's Avatar
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    Brake assist inact...OBC/MID

    It was about 100F today and I got a brake assist inact. OBC message, warning light and aural warning. It reset and went off a number of times.

    About 3 years ago the same thing happened when I was stuck in Summer traffic in DC. It never happened again until today???

    Anyone think the ambient temps are "messing with" the pressure sensors?
    Tom


  2. #2
    mac840
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    Re: Brake assist inact...OBC/MID

    Usually this is when the brake bomb has failed. Has it been replaced ever?

  3. #3
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    Re: Brake assist inact...OBC/MID

    COMPLETE brake system replaced by reputable BMW dealeship paid for by my (former) independent shop...after they put brake fluid in the Pontocin resevoir.

    Any way, the system fixed itself (after cooling down).
    So I am wondering what (excessive) temperatures make this happen once in every 3-4 years.

  4. #4
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    belt slippage?

    FWIW, I've gotten this message as a result of belt slippage. I suppose temperature could affect belt tension/friction.
    Jann - Los Angeles
    '91 850i
    '91 750il
    '88 Mustang LX
    '71 Chevelle

  5. #5
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    Re: belt slippage?

    I like that idea...I hear no noise...but it may be quick/subtle.
    I may just give the tensioner a little tweak!

  6. #6
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    Re: belt slippage?

    Yeah -- my belts were old and glazed when I got the car. I started getting the error in hot, moist weather on my cross-country drive back. Replaced the belts and the message never came back.
    Jann - Los Angeles
    '91 850i
    '91 750il
    '88 Mustang LX
    '71 Chevelle

  7. #7
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    Another Summer...another Brake Assist warning

    I think/hope its a wire or a (pressure) sensor.
    Only when its hot...and when I move the steering wheel.
    Does anyone know which sensor I could try to replace?
    Diagnostics?
    Thanks

  8. #8
    Koizumi
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    Check the seam between the master cylinder and

    Check the seam between the master cylinder and brake booster. There is a weep hole there. Run your finger across it, any fluid? Even a tiny itty bitty bit? Failed O-Rings in the booster (there are 2 replaceable ones, not just 1) is the cause.


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    SWAG- try bleeding the hydraulics if you have

    ASC+T; there's a bleed screw near the left strut top. Otherwise, maybe it's the sensors/switches on the pressure regulator block, same location.

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