GM Service Manual Online
For 1990-2009 cars only

Caution: Refer to Brake Fluid Irritant Caution in the Preface section.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in the Preface section.

Removal Procedure

  1. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
  2. Remove the cover from the underhood electrical center.

  3. Object Number: 890955  Size: SH
  4. Pull back on the connector position assurance (CPA) tab of the electrical connector, then disconnect the connector from the brake fluid level sensor.

  5. Object Number: 891899  Size: SH
  6. Remove the underhood electrical center bracket from the vehicle and reposition the electrical center (1) to access the brake master cylinder. Refer to Underhood Electrical Center or Junction Block Bracket Replacement .

  7. Object Number: 891927  Size: SH
  8. Remove the brake master cylinder auxiliary reservoir. Refer to Brake Master Cylinder Auxiliary Reservoir Replacement .
  9. Disconnect the brake pipes (1) from the master cylinder.
  10. Cap the open brake pipe fitting ends to prevent brake fluid loss and contamination.

  11. Object Number: 890967  Size: SH
  12. Remove the master cylinder mounting nuts.
  13. Remove the master cylinder from the vacuum brake booster.

  14. Object Number: 890969  Size: SH
  15. If the master cylinder is to be reused, inspect the master cylinder-to-vacuum brake booster seal (1) for damage. Replace the seal (1) if necessary.

Installation Procedure


    Object Number: 890969  Size: SH
  1. Bench bleed the master cylinder. Refer to Master Cylinder Bench Bleeding .
  2. Check to ensure that the master cylinder-to-vacuum brake booster seal (1) is properly seated into the recessed groove on the master cylinder.

  3. Object Number: 890967  Size: SH
  4. Install the master cylinder to the vacuum brake booster.
  5. Notice: Refer to Fastener Notice in the Preface section.

  6. Install the brake master cylinder mounting nuts.
  7. Tighten
    Tighten the nuts to 20 N·m (15 lb ft).


    Object Number: 891927  Size: SH
  8. Remove the caps from the brake pipe ends.
  9. Connect the brake pipe fittings (1) at the master cylinder.
  10. Tighten
    Tighten the fittings to 18 N·m (13 lb ft).

  11. Install the brake master cylinder auxiliary reservoir. Refer to Brake Master Cylinder Auxiliary Reservoir Replacement .

  12. Object Number: 891899  Size: SH
  13. Install the underhood electrical center bracket to the vehicle and install the electrical center (1) into position on the bracket. Refer to Underhood Electrical Center or Junction Block Bracket Replacement .

  14. Object Number: 890955  Size: SH
  15. Connect the electrical connector to the brake fluid level sensor, then press forward on the CPA tab of the connector to secure.
  16. Install the cover to the underhood electrical center.
  17. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
  18. Bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding .