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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1322 (Hydraulic Brake System) >> Repair Instructions >> Power Brake Booster Pump Fluid Accumulator Replacement (Two-mode Hybrid) >> Removal Procedure

Removal Procedure

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: The high pressure accumulator (HPA) and the chambers of the brake modulator assembly to which it attaches, store brake fluid at extremely high pressures. Fluid pressure must be relieved before attempting to service the HPA. Ensure that the recommended procedures are followed to relieve system pressure, including using the manual pressure release steps. Failure to properly follow procedures to depressurize the system may result in personal injury.
WARNING: Refer to Brake Fluid Irritant Warning .
CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution .
    NOTE: The ignition must be in the OFF position, without pausing at ACCESSORY, and without applying the brake pedal to ensure the brake modulator and high pressure accumulator (HPA) pressure relief occurs. This process will take approximately 1 to 3 minutes.
  1. Turn the ignition to OFF, without pausing at ACCESSORY, and remove the ignition key.
  2. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
    3. Fig 1: View Of Brake Modulator Manual Pressure Relief Valve
    GM2037952Courtesy of GENERAL MOTORS CORP.
  3. Clean any dirt and debris from the brake modulator assembly and the HPA.
    4. NOTE: To ensure brake modulator and HPA pressure relief has occurred, the manual pressure relief valve must be opened momentarily.
  4. Loosen the manual pressure relief valve (1) 1/4 turn counterclockwise.
  5. Seat, but do not tighten, the manual pressure relief valve.
    6. NOTE: Adequately support the brake modulator assembly to avoid placing stress on the brake pipes and hoses.
  6. Without disconnecting the brake pipes and hoses, remove the brake pressure modulator assembly bracket. Refer to Brake Pressure Modulator Valve Replacement .
    7. Fig 2: View Of High Pressure Accumulator (HPA)
    GM2037950Courtesy of GENERAL MOTORS CORP.
  7. Remove the HPA (1).
    8. Fig 3: Identifying High Pressure Accumulator (HPA) O-Ring
    GM2037951Courtesy of GENERAL MOTORS CORP.
  8. Remove and discard the HPA O-ring seal (1).
  9. Remove any debris from the O-ring seal groove in the brake modulator assembly with a clean, lint-free shop cloth.
  10. If replacing the HPA, properly render inert and dispose of the HPA. Refer to Power Brake Booster Pump Fluid Accumulator Disposal .
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