Top Anti-Lock Brake System Questions

  • Can I tell what type of system it is just by looking at the part number?

    Yes.
  • What type of fluid should I use?

    DOT 3, as a rule always use the fluid recommended by the manufacturer which is located on the Master Cylinder lid.
  • Can I use different size tires?

    NO! Different tire sizes will give false readings to the ABS controller. This will cause inaccurate wheel speed readings. Always check tire size before ABS service.
  • Do I need to depressurize the system before brake service?

    Yes, but only for Integral units with an electric pump and accumulator.

    Note: Not necessary for Non-Integral units (add-on units with normal Brake Boosters and Brake System).

  • How do I depressurize the system?

    First turn the ignition switch OFF. Next firmly apply and release the brake pedal 40 or more complete strokes. A noticeable change in brake pedal feel will occur when the accumulator is completely discharged.
  • Should the brake fluid be changed regularly?

    Yes, every two years/24,000 miles or when brake service is required.
  • I purchased a 12-1000 and the unit has something rattling in it when I shake it, why?

    There is a desiccant pack installed in each unit. This packet is designed to absorb moisture. This is normal.
  • I have a low pedal on a RWAL system, I changed the Master Cylinder and bled the system and the pedal is still low, why?

    Most likely contamination is in the system’s control valve holding the dump valve off it’s seat. This allows rear brake pressure to be released into the accumulator. Isolate the system to determine root cause.
  • I have a GM RWAL two wheel drive with an automatic transmission that has a sinking pedal accompanied by several distinct clicks and a flashing brake warning light, what’s the problem?

    Contamination on the speed sensor inside the transmission (axle on Ford RABS). The sensor is picking up metal filings in the fluid. This distorts the signal and tricks the ABS controller into believing that the rear wheels are locking up.
  • I checked a GM RWAL for trouble codes and now the brake warning light is on and a code 9 is stored. It had no codes before. What’s the problem?

    When manual trouble code diagnosis indicates no codes stored, removal of jumper tool will set a false code 9. To clear the code the ABS module must be reset. Turn off ignition switch Remove ABS module brake fuse Wait 10 seconds and re-install fuse.

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