Bleeding Problem May Be Encountered

A problem may be encountered in bleeding the Powermaster unit if for any reason the pump has not been properly filled with brake fluid. If after any service or new installation the pump does not circulate fluid within 20 seconds motor run time, it may be necessary to reprime the pump. In order to reprime the system, the following steps should be followed:

A. Turn ignition off.

B. Apply the brake pedal with medium to firm pressure 10-15 times to de-pressurize the system. Check reservoir level and fill if required.

C. Clean and remove the reservoir cover.

D. Disconnect the booster tube and nut assembly from the casting boss at the pump outlet located adjacent to the pressure switch assembly (Figure 1).

E. Wait for brake fluid to appear from the disconnected outlet normal gravity bleeding.

F. When brake fluid begins to flow, reconnect the tube nut and torque to 17 N-m (13 lb.ft.).

G. Recheck the fluid level in the reservoir and add new brake fluid as needed. Reinstall the reservoir cover.

H. Turn ignition on. The pump should now fill the accumulator properly and shut off within 15 seconds. The fluid level on the inboard pump reservoir should diminish. (DO Not refill. Gauge marks are only to be used with de-pressurized system.)

I. Continue with Service Manual bleed and fill procedures.

Part Availability:

Parts are currently available from GMSPO except for part number 18011279 expected to be available on 2/8/93.