GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Safari - 2WD 🢒 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 one direction and then in the other.
  3. Turn the engine off. Let the vehicle sit for an hour.
  4. Perform two power assisted applications with the engine off.
  5. If the accumulator failed to hold a charge after one hour, but functions normally after charging, the accumulator valves are malfunctioning.

    6. 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 Overhaul .
  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. In order to repair this condition:

    6.1. Disassemble the power brake booster. Refer to Power Brake Booster Replacement .
    6.2. Replace the accumulator valves. Refer to Hydraulic Brake Booster Overhaul .
  7. Empty the accumulator by pressing the brake pedal several times.
  8. The accumulator can will rotate or wobble if the accumulator has lost its gas charge. This requires replacement of the accumulator. Refer to Hydraulic Brake Booster Overhaul .