GM: Electra/Park Avenue/Ninety-Eight 1990-1993

Depressurizing the Hydraulic Unit


The abs pump/motor assembly will keep the accumulator charged to a pressure between approximately 2000 and 2600 psi any time the ignition is in the on or run position. The pump/motor cannot operate if the ignition is off or if a battery cable is disconnected.

  1. With the ignition off or the negative battery cable disconnected, pump the brake pedal a minimum of 25 times using at least 50 lbs. of pedal force each time.
  3. A definite increase in pedal effort will be felt as the accumulator becomes discharged.
  5. After the increased pedal effort occurs, continue with 5-10 additional brake applications to release any remaining pressure.