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Thread: Replacing brake booster - HELP!

  1. #1
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    Replacing brake booster - HELP!

    I'm replacing my brake booster in my '99 E36 M3 IP race car.

    I've removed the master cylinder from the brake booster and disconnect the vacuum hose and sensor wire. I've also removed the clevis that attaches the booster to the brake pedal as well as the four nuts behind the pedal.

    Bentley says I also need to remove my ABS hydraulic unit from the engine compartment, but gives me no instructions on how to do that.

    The booster is all set to come out and the new one is ready to go in.

    Any help would be appreciated.

    Thanks.

  2. #2
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    bump - anyone?

  3. #3
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    Wish I could help. I'm considering this to help with brake pedal dive. Did you get it replaced?

  4. #4
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    I've moved this to the track forum in hopes that someone may have BTDT. If you don't get any help and/or would like to be back in E36M3, just PM me and I'll move it back.

    Jay

    From wannabe to has been in a few short years..... the older I get, the faster I was

  5. #5
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    Quote Originally Posted by dbbmwm3 View Post
    I'm replacing my brake booster in my '99 E36 M3 IP race car.

    I've removed the master cylinder from the brake booster and disconnect the vacuum hose and sensor wire. I've also removed the clevis that attaches the booster to the brake pedal as well as the four nuts behind the pedal.

    Bentley says I also need to remove my ABS hydraulic unit from the engine compartment, but gives me no instructions on how to do that.

    The booster is all set to come out and the new one is ready to go in.

    Any help would be appreciated.

    Thanks.

    I just had mine pulled while the car was in the shop so I could re-wire the pump. Anyway, it looked quite easy to remove the pump.
    From what I could tell, just take all the lines off, unplug the harness connector. I can't remember if it's 2 or 4 bolts that hold the pump to the base. Either way, just loosen and remove the pump.

    On my S50B32 (euro engine), they had to remove the intake boot to make room. You shouldn't need to remove the plenum.

    Should be really simple.

    **Someone mentioned that using those rubber caps that are used for wire closet shelving work perfectly for fitting over the brake lines and will prevent fluid loss.

    Good luck with your restoration. I'm curious, how did you know that your booster was the issue?

  6. #6
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    Denis, you can do it without removing the ABS pump. Takes some wiggling and patience though. Not sure if 99s are any different than 95s, I suspect them to be the same.
    Eric WONGer
    2012 NASA Nationals GTS3 First Loser
    EX-#121 IP/GTS3 M3 SOLD
    Now-#121 GTS3 E46 M3

  7. #7
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    Thanks guys. I was finally able to do it. Not the hardest job, but not the easiest either.

    After I removed my throttle body elbow and HFM, I was able to see that the ABS pump is secured with a single bolt. Undo that bolt and wiggle the pump from the two prongs that go into rubber grommets in the back and it comes out (that is after disconnecting the four hardlines that send fluid to the four wheels. Once the ABS pump was out, removing and replacing the booster was pretty easy. I don't think there would have been enough room on my car to remove the booster w/o removing the ABS pump.

    Why did I replace it? For the past year, I've been suffering from a soft pedal. During the recent club race at VIR, James Clay drove my car and diagnosed the problem as a bad or going bad brake booster.

    Since the booster was out, I also replaced the one-way vacuum check valve too. I was debating replacing my master cylinder, but decided against that. If it's bad too, that's a very easy swap out for a new one.

    That's one project I hope to never do again! Now, onto replacing my front control arms and working on my diff

  8. #8
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    Quote Originally Posted by dbbmwm3 View Post
    Why did I replace it? For the past year, I've been suffering from a soft pedal. During the recent club race at VIR, James Clay drove my car and diagnosed the problem as a bad or going bad brake booster.
    James made the same diagnosis on my car It feels SO much better now!

    You coming up to Summit Point?
    Eric WONGer
    2012 NASA Nationals GTS3 First Loser
    EX-#121 IP/GTS3 M3 SOLD
    Now-#121 GTS3 E46 M3

  9. #9
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    Quote Originally Posted by magnetic1 View Post
    James made the same diagnosis on my car It feels SO much better now!

    You coming up to Summit Point?
    Yeah, I remember that from a while back. It makes NO sense how a bad booster can cause a soft or sinking pedal, but hey, it works! Same goes for E30's with a soft or sinking pedal, but you can simply adjust the clevis/pushrod to cure it.
    James Muskopf
    RRT Racing
    DC Metro's premier BMW service and racing facility

  10. #10
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    Quote Originally Posted by magnetic1 View Post
    You coming up to Summit Point?
    I am! Hopefully all the kinks will be sorted out by then and I can run a mechanically free weekend

  11. #11
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    Quote Originally Posted by dbbmwm3 View Post
    I am! Hopefully all the kinks will be sorted out by then and I can run a mechanically free weekend
    Denis:

    I hate to be the bearer of bad news, BUT there are no "mechanically free" things in racing. All the mechanical stuff cost $$$$.

    Hope you are getting it together. My turn around will be done next week.

    Chris
    #175 CM E46 M3
    Former Knee Dragger
    Real name= Chris P. Lewis
    Occupation= Green House Gas Creator, but I planted a GARDEN last year.
    "When you live inside a vacuum, nothing sucks"
    http://flickr.com/photos/8150451@N03...7602830737584/

  12. #12
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    Quote Originally Posted by JamesM3M5 View Post
    Yeah, I remember that from a while back. It makes NO sense how a bad booster can cause a soft or sinking pedal, but hey, it works! Same goes for E30's with a soft or sinking pedal, but you can simply adjust the clevis/pushrod to cure it.
    So is this the ultimate answer to all (or most) of the "My E36 has a sinking pedal" issues? Seems like some people blame wheel bearings/pad knock-back, some claim that an aftermarket BBK is the only way to fix it, etc. I've rebuilt all my calipers and replaced my master cylinder, and the problem is still there. I am replacing wheel bearings in a week or two. I hope I'm not on the hook for a booster as well.

    -tammer <--wishes the E36 had as nice a pedal as the E28s do ...

  13. #13
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    Quote Originally Posted by tammer View Post
    So is this the ultimate answer to all (or most) of the "My E36 has a sinking pedal" issues? Seems like some people blame wheel bearings/pad knock-back, some claim that an aftermarket BBK is the only way to fix it, etc. I've rebuilt all my calipers and replaced my master cylinder, and the problem is still there. I am replacing wheel bearings in a week or two. I hope I'm not on the hook for a booster as well.

    -tammer <--wishes the E36 had as nice a pedal as the E28s do ...
    I replaced EVERYTHING. Nothing worked until I replaced the booster.
    Eric WONGer
    2012 NASA Nationals GTS3 First Loser
    EX-#121 IP/GTS3 M3 SOLD
    Now-#121 GTS3 E46 M3

  14. #14
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    Looks like I'm next. My car has sucky pedal feel. If I really stand on it I can push the pedal practically all the way to the floor. The car stops good but the pedal is not confidence inspiring. PFC01 pads, Zimmerman solid rotors, brass bushings, stainless lines, rebuilt calipers with stainless pistons in front, Motul RBF600 fluid flushed repeatedly, etc.

    I think I'm going to bypass the front hubs and go straight to the brake booster. It's $476 at Pelican Parts. Does that sound about right?

  15. #15
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    Quote Originally Posted by CP Louie View Post
    Denis:

    I hate to be the bearer of bad news, BUT there are no "mechanically free" things in racing. All the mechanical stuff cost $$$$.

    Hope you are getting it together. My turn around will be done next week.

    Chris

    Now someone tells me this... jeez, I'm going to sell the car and take up golf

    Brake booster, front control arms and rear diff are done... well except for the halfshaft torx bolt that stretched and snapped in half All that's left is to remove/fix that bolt and get my RTAB carrier mounts fixed/reinforced.

    Can't wait to get back on track!

    -Denis

  16. #16
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    This is wild that the booster is bad if the pedal is getting soft. You'd think it would be just the opposite. I'm confused.

    I guess there could be a valve that's bleeding off too much pressure?!

  17. #17
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    I replaced my booster last year on the M3 (same mushy pedal symptoms), and seemed to cure the problem, but I also repaced the MC at the same time. I've just put that old booster on the 328 after we swapped the ABS to the older 3 channel (I needed the pedal travel sensor, and the 328 system does not have one). I'll see how the pedal is on May 6th, and replace the booster with a new on if it's crap. That would give definitl proof for me that the booster can be the casue!
    Check out the 8legs Racing page: https://www.facebook.com/8legsRacing/


  18. #18
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    Quote Originally Posted by ScotcH View Post
    I replaced my booster last year on the M3 (same mushy pedal symptoms), and seemed to cure the problem, but I also repaced the MC at the same time. I've just put that old booster on the 328 after we swapped the ABS to the older 3 channel (I needed the pedal travel sensor, and the 328 system does not have one). I'll see how the pedal is on May 6th, and replace the booster with a new on if it's crap. That would give definitl proof for me that the booster can be the casue!
    My Master Cylinder is OE 100+k miles I only changed my booster. Though I do have a spare MC just in case.
    Eric WONGer
    2012 NASA Nationals GTS3 First Loser
    EX-#121 IP/GTS3 M3 SOLD
    Now-#121 GTS3 E46 M3

  19. #19
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    Guys I am having the mushy pedal as well. New pads/rotors etc. My initial pedal sucks, takes a lot of pressure to really get the brakes to stop and I can basically get it to touch the floor. I am really frustrated because I too am not sure if its the mc or the booster or something so miniscule. I pumped the brakes with the car off and the pedal got firm and stayed firm, thats usually a good test to see if the booster is good right? Did anybodym else try this with the same result, then proceed to replace th booster and it ended up fixing the problem?

    Please help, track day is coming up.
    TIA.

  20. #20
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    Quote Originally Posted by savage217 View Post
    Guys I am having the mushy pedal as well. New pads/rotors etc. My initial pedal sucks, takes a lot of pressure to really get the brakes to stop and I can basically get it to touch the floor. I am really frustrated because I too am not sure if its the mc or the booster or something so miniscule. I pumped the brakes with the car off and the pedal got firm and stayed firm, thats usually a good test to see if the booster is good right? Did anybodym else try this with the same result, then proceed to replace th booster and it ended up fixing the problem?

    Please help, track day is coming up.
    TIA.
    Have you bleed your system really well?

  21. #21
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    Quote Originally Posted by dbbmwm3 View Post
    Have you bleed your system really well?
    Yes I have. I havent used a pressure bleeder but I did use a vacuum bleeder as well as the old fashioned way and got out every air bubble.

  22. #22
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    Savage, you've described my problem exactly. My new brake booster should be here today. I'm not sure when I can get to replacing it but hopefully in the next week. I'll post my results as soon as possible.

  23. #23
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    Quote Originally Posted by Tronix View Post
    Savage, you've described my problem exactly. My new brake booster should be here today. I'm not sure when I can get to replacing it but hopefully in the next week. I'll post my results as soon as possible.

    My track day is may 22, hopefully I have it fixed by then. Cant wait to hear your results.

  24. #24
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    Quote Originally Posted by JamesM3M5 View Post
    Same goes for E30's with a soft or sinking pedal, but you can simply adjust the clevis/pushrod to cure it.
    So can you adjust the clevis/pushrod on an e36? Is there any adjustment for the brake pedal to make it higher or are the e30's the only one really

  25. #25
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    Found out there is no adjustment on the e36 brake pedal. Guys I am really on the fence with this. I dont wanna spend 400 dollars on a master cylinder and find out its the booster or something else. Ive talked to a lot of educated people and everyone thinks it sounds like a master cylinder issue and not a booster issue. Is it possible that the guys that replaced the booster's had air in the system all along and that since you need to take the master cylinder out and then bleed it, that there was air in the line somewhere all along? Its just hard to believe that a booster is the issue because frankly almost everyone and all signs point to the master cylinder.

    I was planning on maybe throwing a good used master cylinder on the car and seeing how it feels with that, if the problem is still there, new booster it is. If the problem is fixed with the used master, Ill just buy a new master cylinder and take the used one off. Anyone else do something like this? Really trying to get to the bottom of this PIA.

    Thanks a bunch.

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