GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Sierra - 4WD 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Accumulator Leak-Down Test
  1. Start the engine.
  2. Charge the accumulator by pressing the brake pedal or by completely turning the steering wheel in 1 direction and then in the other.
  3. Turn the engine off. Let the vehicle sit for an hour.
  4. Perform 2 power assisted applications with the engine off.
  5. If the accumulator fails to hold a charge after 1 hour, but functions normally after charging, the accumulator valves are malfunctioning.

    6. Use the following procedure in order to repair this condition:

    5.1. Disassemble the power brake booster. Refer to Power Brake Booster Replacement .
    5.2. Replace the accumulator valves. Refer to Hydraulic Brake Booster Accumulator Replacement .
  6. If the charging and discharging of the accumulator is audible, but the accumulator still fails to hold a charge, the accumulator valves are malfunctioning.

    7. Use the following procedure in order to repair the malfunction:

    6.1. Disassemble the power brake booster. Refer to Power Brake Booster Replacement .
    6.2. Replace the accumulator valves. Refer to Hydraulic Brake Booster Accumulator Replacement .
  7. Press the brake pedal 30 times in order to empty the accumulator.
  8. The accumulator can will rotate or wobble if the accumulator has lost the gas charge. Replace the accumulator if there is rotating or wobbling present. Refer to Hydraulic Brake Booster Accumulator Replacement .