GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2009 🢒 G8 🢒 Preface 🢒 Dangers, Warnings, and Cautions 🢒 Master Cylinder Replacement

Removal Procedure

    Warning: Refer to Battery Disconnect Warning in the Preface section.

  1. Disconnect the battery ground cable. Refer to Battery Negative Cable Disconnection and Connection.

    2. Warning: Refer to Brake Fluid Warning in the Preface section.

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

    Caution: Refer to Adding Fluid to the Brake System Caution in the Preface section.

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

  2. Apply the park brake and chock the wheels.

    3. Note: With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal effort increases significantly, in order to deplete the vacuum brake booster power reserve.

  3. Deplete the vacuum brake booster power reserve.
  4. Clean the master cylinder, around the brake lines and the reservoir cap.
  5. Place a clean suitable container under the master cylinder.
  6. Remove the master cylinder reservoir cap.

    7. Object Number: 1943726 Size: SH
  7. Siphon the brake fluid out of the master cylinder reservoir (1) using a hand vacuum pump (2).

    8. Object Number: 1943729 Size: SH

    Note:  Lift the connector security clip with a suitable tool or equivalent to release the brake fluid level switch electrical connector (8) from the brake fluid level switch.

  8. Disconnect the brake fluid level switch electrical connector (4).
  9. Disconnect the brake pipes from the master cylinder (2).

    10. Note:  Install a rubber cap or plug on the exposed brake pipes (3) in order to prevent fluid loss and contamination.

  10. Plug both the exposed brake pipes.
  11. Remove the strut tower to master cylinder support bracket retaining nuts (7).
  12. Remove the master cylinder support bracket to master cylinder retaining bolt (5).
  13. Remove the master cylinder support bracket (5).
  14. Remove the master cylinder to vacuum brake booster retaining nuts (1, 3).
  15. Remove the master cylinder (2) from the vacuum brake booster.

    16. Object Number: 1943735 Size: SH

    Caution: Do not disturb the brake booster push rod or press the brake pedal when the master cylinder is removed, internal damage to the brake booster may occur.

    Note: The vacuum brake booster to master cylinder sealing O-ring (1) is a single use only component and will not reseal. Install a NEW master cylinder sealing O-ring (1) whenever the master cylinder (2) is removed from the vacuum brake booster.

  16. Remove the vacuum brake booster to master cylinder sealing O-ring (1) from the master cylinder (2).

    17. Discard the master cylinder sealing O-ring (1).

Installation Procedure

    Warning: Refer to Brake Fluid Warning in the Preface section.

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

    Caution: Refer to Adding Fluid to the Brake System Caution in the Preface section.

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

  1. Install the master cylinder reservoir. Refer to Master Cylinder Reservoir Replacement.
  2. Bench bleed the master cylinder. Refer to Master Cylinder Bench Bleeding.

    3. Object Number: 1943735 Size: SH
  3. Install a NEW vacuum brake booster to master cylinder sealing O-ring (1) to the master cylinder (2).
  4. Place a clean suitable container under the master cylinder (2).

    5. Object Number: 1943729 Size: SH

    Caution: Do not disturb the brake booster push rod or press the brake pedal when the master cylinder is removed, internal damage to the brake booster may occur.

  5. Install the master cylinder (2) to the vacuum brake booster.

    6. Caution: Refer to Fastener Caution in the Preface section.

  6. Install the master cylinder to vacuum brake booster retaining nuts (1, 3) and tighten to 10 N·m (89 lb in).
  7. Install the master cylinder support bracket (6).
  8. Install the master cylinder support bracket to strut tower retaining nuts (7) and tighten to 23 N·m (17 lb ft).
  9. Install the master cylinder support bracket to master cylinder retaining bolt (5) and tighten to 17 N·m (13 lb ft).
  10. Remove the rubber caps from the exposed brake pipes.
  11. Connect the brake pipes to the master cylinder (2) and tighten to 15 N·m (11 lb ft).
  12. Connect brake fluid level switch electrical connector (3).

    13. Make sure the security clip is correctly installed.

  13. Connect the battery ground cable. Refer to Battery Negative Cable Disconnection and Connection.
  14. Bleed the braking system. Refer to Hydraulic Brake System Bleeding.
  15. Release the park brake and remove the wheel chocks.