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Thread: Brake Assist Inact.???

  1. #1
    Join Date
    Jan 2004
    Location
    Toronto, Canada
    Posts
    1,330
    My Cars
    BMW 850CSi

    Brake Assist Inact.???

    After accelerating briskly in second gear up to 6000rpm and back down again, I received the Brake Assist Inact. Message on the MID display and have no power brakes nor power steering. The brake pedal is rock hard and requires heavy pressure to even slow down the car. The light goes out if I rev the engine above 3000rpm, but still no power assist. The Pentosin reservoir is full.

    Where do I start to look? Brake bomb?

  2. #2
    Join Date
    Jun 2008
    Location
    SF Bay Area
    Posts
    3,790
    My Cars
    Supercharged 850ci
    Its the brake bomb...
    Wish fcp euro did another order of cheaper units from eu... damn things are close to 400 now

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  3. #3
    Join Date
    Jan 2004
    Location
    Toronto, Canada
    Posts
    1,330
    My Cars
    BMW 850CSi
    Was able to get the power steering and power brake function back online by getting the rpms over 3000 while negotiating a curve (applying manual pressure to the steering wheel) and the power steering suddenly just kicked in (along with full power brakes). How do I know it’s not the PS pump?

  4. #4
    Join Date
    Jul 2007
    Location
    Cave Creek, AZ
    Posts
    1,117
    My Cars
    1993 850ci 2001 M5 / Z3M
    Is it possible that one of the filters in the hydraulic system are clogged, there is one in the main canister where fluid is filled, and another at the bottom of the engine in a brass canister?

    When was the last time you replaced fluid and what is the condition of your hoses?
    Regards,

    Brian
    Cave Creek, AZ

  5. #5
    Join Date
    Jan 2004
    Location
    Toronto, Canada
    Posts
    1,330
    My Cars
    BMW 850CSi
    Quote Originally Posted by bdiefAZ View Post
    Is it possible that one of the filters in the hydraulic system are clogged, there is one in the main canister where fluid is filled, and another at the bottom of the engine in a brass canister?

    When was the last time you replaced fluid and what is the condition of your hoses?
    Yes, it’s been a long while since the 2 filters were replaced (~8 years?). That will be first on the to-do list.


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  6. #6
    Join Date
    Oct 2008
    Location
    Madrid - SPAIN
    Posts
    366
    My Cars
    850iA - 1990
    Are your belt tensioners ok ? In my car ir was due to a weak tensioner making the belt to slip...

  7. #7
    Join Date
    Jan 2004
    Location
    Toronto, Canada
    Posts
    1,330
    My Cars
    BMW 850CSi

    Brake Assist Inact.???

    Quote Originally Posted by dudu850 View Post
    Are your belt tensioners ok ? In my car ir was due to a weak tensioner making the belt to slip...
    Yeah the alternator tensioner is 1yr old. A/C one is new. Need to replace the belt thou


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    Last edited by Dr. T; 04-27-2018 at 05:15 PM.

  8. #8
    Join Date
    Jul 2007
    Location
    Cave Creek, AZ
    Posts
    1,117
    My Cars
    1993 850ci 2001 M5 / Z3M
    Keep us posted after new belts, fluids, and filters for the system.
    Regards,

    Brian
    Cave Creek, AZ

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