GM Service Manual Online
For 1990-2009 cars only

Removal Procedure

    Caution: When servicing brake parts, do not create dust by grinding or sanding brake linings, by cleaning brake parts with a dry brush or with compressed air. Many earlier models or aftermarket brake parts may contain asbestos fibers which can become airborne if dust is created during servicing. Breathing dust containing asbestos fibers may cause serious bodily harm. A water dampened cloth or water based solution should be used to remove any dust on brake parts. Equipment is commercially available to perform this washing function. These wet methods will prevent fibers from becoming airborne.

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  1. Remove the master cylinder reservoir, if necessary. Refer to Master Cylinder Reservoir Replacement .

  2. Object Number: 188367  Size: SH
  3. Remove the proportioner valve caps (1).

  4. Object Number: 188779  Size: SH
  5. Remove the proportioner valve cap O-rings (1). Discard the O-rings.

  6. Object Number: 188787  Size: SH
  7. Remove the proportioner valve piston springs (1).

  8. Object Number: 188790  Size: SH
  9. Remove the proportioner valve pistons (1) using needle nose pliers. Do not scratch or damage the piston stems.

  10. Object Number: 188794  Size: SH
  11. Remove the proportioner valve seals (1) from the proportioner valve pistons.
  12. Clean all of the components with denatured alcohol.
  13. Dry all of the components with non-lubricated, compressed air.
  14. Inspect the proportioner valve pistons for corrosion or deformation.
  15. Replace any components if defects are found.

Installation Procedure


    Object Number: 165380  Size: SH
  1. Lubricate the new proportioner valve cap O-rings (5) and proportioner valve seals (4) with the silicone grease that is supplied in the repair kit.
  2. Lubricate the stem of the proportioner valve pistons (1).

  3. Object Number: 188794  Size: SH
  4. Connect the new proportioner valve seals (1) on the proportioner valve pistons.
  5. Install the proportioner valve pistons with the seal lips facing upward toward the proportioner valve cap.


    Object Number: 188790  Size: SH
  6. Install the proportioner valve pistons (1) and the seals in the master cylinder body.

  7. Object Number: 188787  Size: SH
  8. Install the proportioner valve piston springs (1) in the master cylinder body.

  9. Object Number: 188779  Size: SH
  10. Connect the new proportioner valve cap O-rings (1) in the grooves in the proportioner valve caps.

  11. Object Number: 188367  Size: SH

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  12. Install the proportioner valve caps (1) in the master cylinder body.
  13. Tighten
    Tighten the proportioner valve caps to 27 N·m (20 lb ft).

  14. Install the master cylinder reservoir if necessary. Refer to Master Cylinder Reservoir Replacement .