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5350Re: ABS query

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  • doug
    Feb 10, 2010

      My experience (85 e28 535) is that the sensor "gears" can be effectively
      cleaned with a wire brush, as long as they haven't rusted away.

      The failure mode is usually corrosion inside the poorly sealed hole in the
      wheel hub that holds the sensor, which gradually compresses the metal sensor
      cans until they fail. Getting them out can be a PITA, so don't expect
      save/clean/repair them.

      BMW has a special tool that plugs into the ABS harness that will measure the
      sensor voltages to identify the bad one(s). I faked that by connecting a
      voltmeter to the abs harness connector and spinning the wheel with the car
      on jack stands. Its hard to get a consistent rotational velocity to compare
      voltages between wheels, but if the sensor is very bad, it should be pretty
      obvious. On the first occasion, I paid an indie mechanic to use the BMW tool
      to identify the bad sensor. You might try that now to get a written report
      to take back to the local shop.

      When replacing the sensors, use RTV/silicone as a sealant.

      The failure mode appears to be exactly the same on the plastic abs sensors
      on my 2000 e39 540i-6 (both rear sensors failed by 65k miles), so don't
      expect any improvement on your next BMW. On the other hand, the newer cars
      are so complicated, you can identify the failed sensor by what other
      functionality stops, e.g. speedo or cruise. Sigh.


      Waterloo, Ontario Canada, eh

      86 951 (https://reg.pcaucr.org/forum/post.jsp?postid=2393)
      01 E320 (W210) 4matic Wagon
      00 540i-6 (http:// www.trillium-bmwclub.ca/forum/post.jsp?postid=1916)
      94 855 turbo Wagon (sold in 09)
      85 535i-5 (sold in 07)
      83 944 (sold in 86)
      I apparently only buy cars designated by numbers
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