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Thread: Brake "Bomb" Accumulator

  1. #1
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    Brake "Bomb" Accumulator

    So I am well aware of the common issue. Hard pedal that becomes soft/normal after a few seconds.
    Purchased a used one, had it installed, new fluid. better, but not 100%... What next? The pressure switch? Is there 1 or 2? Where to go.. My mechanic is claiming it could be the brake master cylinder, but at nearly 1000$ I am not so sure I want to try it just yet.
    Any help would be appreciated..
    ['07 BMW M5/6.:Indianapolis Red/Black:.
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  2. #2
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    From your description of the problem it looks like the brake master cylinder. There are 4 seals inside and some other parts, I posted the details here in post 7 https://www.bimmerforums.com/forum/s...inder+bakelite
    instead of repairing and sourcing the rare gaskets which are officially not available, get a reman one. Or contact master6 if he repairs them too, he repairs the brake booster units.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    Quote Originally Posted by shogun View Post
    From your description of the problem it looks like the brake master cylinder. There are 4 seals inside and some other parts, I posted the details here in post 7 https://www.bimmerforums.com/forum/s...inder+bakelite
    instead of repairing and sourcing the rare gaskets which are officially not available, get a reman one. Or contact master6 if he repairs them too, he repairs the brake booster units.
    My mechanic suggested the same. New is 1K$. Any suggestion on who sells reman? I've not been successful. I will send a note to master6.
    Thank you.
    ['07 BMW M5/6.:Indianapolis Red/Black:.
    Toys
    '93 BMW 850i J Spec- (DiamondSchwartz)-CSI Kit- Lowered-Wokke Chips- Custom Exhaust- 18" MK1's-KN Filters+ M Steering Wheel- Stereo Upgrade +++
    94 BMW 850 CSi - OE
    91 BMW 850Ci Manual
    '88 BMW 635CSi ACS's++
    '81 MB 500 SEC Koenig (pearl white)
    00 BMW 750iL J Spec- Alpina Mods
    06 MB S65 AMG
    09 911 4S
    11 BMW M3 DCT Competition
    12 BMW 328i M Sport Convertible
    +++

  4. #4
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    If it's just the master cylinder, you can use one from an e32. It worked well for my 91 850 (no mods, all stock). I believe the only difference is 1mm in the bore size (I didn't notice a change, but don't drive my 8 all that often) It's Under $200 (at least here in the US) and a fairly easy change.

    https://www.bimmerforums.com/forum/s...BMW-850i-(e31)
    My Cars - 1991 BMW 850i - mine for fun, 1993 Saab 900c - mine for fun, 2008 Lexus is250 - my daily driver, 2003 Dodge Durango - my wife's, 1994 Acura Legend - gave it to kid

  5. #5
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    Quote Originally Posted by PabloRock View Post
    If it's just the master cylinder, you can use one from an e32. It worked well for my 91 850 (no mods, all stock). I believe the only difference is 1mm in the bore size (I didn't notice a change, but don't drive my 8 all that often) It's Under $200 (at least here in the US) and a fairly easy change.

    https://www.bimmerforums.com/forum/s...BMW-850i-(e31)
    Yes master brake cylinder.
    ['07 BMW M5/6.:Indianapolis Red/Black:.
    Toys
    '93 BMW 850i J Spec- (DiamondSchwartz)-CSI Kit- Lowered-Wokke Chips- Custom Exhaust- 18" MK1's-KN Filters+ M Steering Wheel- Stereo Upgrade +++
    94 BMW 850 CSi - OE
    91 BMW 850Ci Manual
    '88 BMW 635CSi ACS's++
    '81 MB 500 SEC Koenig (pearl white)
    00 BMW 750iL J Spec- Alpina Mods
    06 MB S65 AMG
    09 911 4S
    11 BMW M3 DCT Competition
    12 BMW 328i M Sport Convertible
    +++

  6. #6
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    Search for 34311156643 and you should find it (it's not the brake bomb, that is the sphere thing that holds pressure. I didn't change that on mine). The MC cured all my braking issues. (the link is a write up of my change). It didn't take all that all to do. A lot of the time goes into bleeding the brakes (unless you have a lift and don't have to move a jack around).
    My Cars - 1991 BMW 850i - mine for fun, 1993 Saab 900c - mine for fun, 2008 Lexus is250 - my daily driver, 2003 Dodge Durango - my wife's, 1994 Acura Legend - gave it to kid

  7. #7
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    Quote Originally Posted by PabloRock View Post
    Search for 34311156643 and you should find it (it's not the brake bomb, that is the sphere thing that holds pressure. I didn't change that on mine). The MC cured all my braking issues. (the link is a write up of my change). It didn't take all that all to do. A lot of the time goes into bleeding the brakes (unless you have a lift and don't have to move a jack around).
    Yes, looked through and already sent the part number to my brother! Hope it all works out! Keeping 2 850's on the road is getting expensive!!!
    ['07 BMW M5/6.:Indianapolis Red/Black:.
    Toys
    '93 BMW 850i J Spec- (DiamondSchwartz)-CSI Kit- Lowered-Wokke Chips- Custom Exhaust- 18" MK1's-KN Filters+ M Steering Wheel- Stereo Upgrade +++
    94 BMW 850 CSi - OE
    91 BMW 850Ci Manual
    '88 BMW 635CSi ACS's++
    '81 MB 500 SEC Koenig (pearl white)
    00 BMW 750iL J Spec- Alpina Mods
    06 MB S65 AMG
    09 911 4S
    11 BMW M3 DCT Competition
    12 BMW 328i M Sport Convertible
    +++

  8. #8
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    Quote Originally Posted by BMWM5LOVER View Post
    Yes, looked through and already sent the part number to my brother! Hope it all works out! Keeping 2 850's on the road is getting expensive!!!
    I've been lucky. I've had my 8 for almost 20 years now with minimal expense. But I think things are starting to catch up with me. Need a new headliner and a "Trans Fail Safe Prog" just started to pop up (hopefully it was just a fluid level thing). Unless you have the $$$$, it's not a car for the average joe. Bringing into the shop for anything is a major expense. That's why I try to do all the work myself. Just learning as I go (and so far no real problems). Good luck with the MC.
    My Cars - 1991 BMW 850i - mine for fun, 1993 Saab 900c - mine for fun, 2008 Lexus is250 - my daily driver, 2003 Dodge Durango - my wife's, 1994 Acura Legend - gave it to kid

  9. #9
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    11/88 E32 750iL+98 E36M3
    ATE for $163 at FCPEURO 34311156643 BMW Brake Master Cylinder - ATE 34311156643 for E32 750, and the older E32 735 with H31 brake booster unit. Part #: ATE-010210
    and the cheapest one for abt. $70 are from Uro, but there I would go for ATE quality, safety is one thing + installation time is the other thing
    Last edited by shogun; 03-27-2019 at 11:29 PM.
    Shogun tricks and tips for the E32 series are HERE!

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