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Thread: Braking

  1. #1
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    Braking

    My brakes are almost complete shit. When i push the peddle down i get no response until the pedal hits the floor. i suspect my master cylinder and brake booster maybe bad. the master cylinder is almost completely covered in rust. i’m having trouble finding a brake booster for a reasonable price. do you think if i just change the master cylinder my brakes will have better response?

  2. #2
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    The experience I've had with other model cars is if the booster goes bad then the pedal is harder to push. I know you've check the fluid level and it's not low or leaking. So I agree with you, the master cylinder is probably bad.

  3. #3
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    Sounds to me like you have a leak in the system and/or water in the fluid and/or air in the system. You should flush the system with fresh fluid, make sure all the air is bled out, then see what you have. You may need to rebuild a caliper or two as well, depending on what shape they're in.
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  4. #4
    richardodn's Avatar
    richardodn is offline Old Guy BMW CCA Member
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    The booster gives assist so that the brakes are easier to push. They really don't do anything for the hydraulic system itself. You likely have a failing master cylinder. Here are some questions.

    1. If you pump the brakes, does pressure in the system build?
    2. After pumping up the brakes and holding the pedal in with constant pressure, does it slowly travel to the floor?
    3. Do you have any fluid leakage? Even if you don't see drips anywhere, if you continually have to add fluid there is a leak.

    If the answer to 1 or 2 is yes, you have a bad master cylinder. This is usually due to internal leakage past the piston seals. If the answer to 3 is also yes and you can't see any leaks, you're leaking internally into the booster and it will fail eventually. In that case, I'd suggest finding a good used unit if a new one is too expensive. But if there is no contamination of fluid into the booster, there's no need to replace it.
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  5. #5
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    there is no leak in my braking system. i will change the master cylinder myself. looking for the part there are many different types of brake master cylinders. how do i know which one to buy? I have a 1986 325e

  6. #6
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    No e30s, again :(
    The autoparts store woll gove you the right one when you tell them the year and make/ model. Or just search for 86 325e on pelican parts or rock auto and it will show the right one

  7. #7
    richardodn's Avatar
    richardodn is offline Old Guy BMW CCA Member
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    Your car should have ABS. The only question is whether you have an ATE system (most likely) or a Lucas/Girling one. Look at your brake booster. Is there a manufacturer sticker or stamping?
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  8. #8
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    Quote Originally Posted by richardodn View Post
    Your car should have ABS. The only question is whether you have an ATE system (most likely) or a Lucas/Girling one. Look at your brake booster. Is there a manufacturer sticker or stamping?
    alright i’ll look into that tomorrow morning but what’s the difference between ATE and girling?

  9. #9
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    different manufacturers of the same system. every auto manufacturer needs more than one supplier of systems by law in case a supplier goes out of business. this is to ensure continuity of replacement parts over the lifespan of the vehicle. it's important to identify the manufacturer as the parts work better together when replaced with original ( the others may not work at all ).

    quick note on rockauto above : watch your brands. rockauto is a reseller of third party manufacturers and as such there is a wide range of quality in the products they sell. i replaced a master cylinder on a vw recently and two new rockauto master cylinders were so poor they did not work right out of the box. wound up pulling one from a wreck to fix it.

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