Re: ABS Brake problems...more info (archive)

The sensors are located on the inside part of the hub. You can trace the wiring to it. It is held on by a screw. Once you unscrew it, you have to be VERY careful pulling the sensor out of it's hole. The sensor is plastic and very fragile and you can break it if you force it out. The reason it's so difficult to pull it out is because there is an O-ring that seals it. Clean it off, put it back on making sure to grease the O-ring.

Now, you'll need to pull the brake disk off to check the pulse wheel. Check for cracks, broken teeth, dirt, out of roundness, etc. Clean off dirt, brake dust, etc. Check for anythign that can cause excessive clearance between the pulse wheel and speed sensor.

Other than getting new ABS sensors (an expensive proposition), cleaning all of this is really the only thing you can do.

You can try to find used set of working ABS sensors and see if replacing them makes any difference. It could be just that one of your sensors is starting to go bad. Troubleshooting a bad sensor is a PITA, unfortunately, and there are no tests or anything that you can do to check them. Of course, the condition of the wiring and plugs is also a big deal as the ABS system is very sensitive to small changes in resistence. This is why if the main ABS wiring harness is damaged, it is best to replace it, rather than trying to fix it, as fixing it could alter resistence values and cause faults.

Chris Graff
Head Coordinator
BMW M535i SIG
www.m535i.org

Sounds like you also have the possible solution for my problem. ABS light came on and system disabled whenever I exceded 75 MPH, now it is down to 40 MPH. Any info on cleaning the sesors and gears or where to find it would be GREATLY appreciated. I have an E30

Jim

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