Crazy brake issue

Hey guys, the front left caliper seems to be grabbing/grinding more than the others. I have replaced all four rotors,calipers and the master cylinder. However, it still seems to grab/grind a bit. I can tell because the rotor has more wear on it.

Its especially noticeable after about 5-10 minutes of driving and braking. I will also hear a squeal coming from the rear. I am assuming that the front caliper is grabbing and not allow the rear calipers to make full contact and thus the vibration is cause the squeal.

I'm about to give up and sell this car. Can anybody help with a solution?
I heard maybe I need new expensive ABS parts?

Thanks. :(

Assume you've bled the brakes profusely and have taken care not to get air in the system? :)

You can pick up the ABS stuff on ebay for not that much dinero. What year/model?

best, whit

Its a 1990 535i.

I don't know what you mean by profusely. I have my wife pump the pedal about 12 times and hold it while I open the bleed screw and let fluid out. I do this about 3 times for each caliper.


Maybe I'm doingit wrong?

After installing the master cylinder, it seems okay for a day and the problem is now back. Almost like air is getting in the system..

Or maybe something to do with the ABS...but I don't know how to troubleshoot a bad ABS.

Quote:

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Originally Posted by lowell

Assume you've bled the brakes profusely and have taken care not to get air in the system? :)

You can pick up the ABS stuff on ebay for not that much dinero. What year/model?

best, whit

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Have you got a Bentley's? There's a quick 'n dirty procedure in there for testing the master cylinder, brake bomb, and associated componentry. Don't quote me on this, but I think it goes something like:

- Pump brake pedal ~ 6 times with engine off and hold it, start the engine and the pedal should drop down for a second and stay firm at that point.

- At idle, push the brake pedal down until it stops. It should stay firm (test the plumbing, obviously).

I'm betting that there's air in there and might have to be pressure bled. It sounds like your procedure is correct, the only thing I do differently is I open the valve, have the helper jam the pedal until new fluid comes out, and then I close it up MID STROKE so that no air goes back into the caliper in the vacuum.

Don't give up yet :)

Also, my pass side front rotor seems to do a little of the same thing. I replaced the caliper as well, but it's not sticking or causing the car to pull. Braking seems very even, or - at least, as even as it can get with the shitty pads I have on there right now.

best, whit

you cant properly bleed these particular ABS systems without a pressure bleed, have to pressurize it to compress the air or something before the ABS which decompresses with each pump of the peddle...I messed with this for 2 big cans of fluid before I figured that out.

Bruno has a cool bleeder deal on his site that I bought, think it was about 20 bux WITH a guage. Problems went away.

this link might work?
http://www.racingking.net/Canada/Scr...sp?idproduct=1