|This was published in the Midlands Chapter GSCA newsletter... it comes from a service bulletin from GM.
The following information was sent to us by our far Western Nebraska member Al Musil (308) 452-3020. He dug up some more information on the infamous Powermaster brakes.
Click on the following for graphical charts to assist with troubleshooting:
|This bulletin provides brake diagnostic information that will help to correctly diagnose and resolve concerns with the PowerMaster brake system on 1986 Estate Wagons and 1985-1987 Regal Turbo vehicles.
"Harder Pedal Feel" or "Increased Pedal Travel"
A. Harder Pedal feel
B. Increased Pedal Travel
NOTE: Replacement of the complete PowerMaster assembly is not required to correct most customer concerns. Part kits are available that will resolve most concerns with this system and eliminate unnecessary replacement of the complete assembly.
Check fluid on booster side after 10 brake applies with ignition off. Check reservoir on the side away from pressure switch
Booster Motor Operation
Inspect for External Leaks
Test for Combination Valve air ingestion
To properly evaluate pedal travel, apply brakes with vehicle parked, ignition off, and without power assist (depressurize accumulator with 10 brake applies). Pedal travel should be 2 1/4" Max. with normally worn brake linings when checked at 100 # pedal force.
|Corrective Action Steps|
|Step #1 - Low fluid in booster side (external leak)
Step #2 - After accumulator Operation Test indicates seven seconds of more of motor operation.
Step #3 - Booster Motor does not run.
Confirm that the 30 Amp fuse is OK or replace. Then conduct electrical circuit checks. Disconnect the pressure switch and motor electrical connector and test to the following:
Step #4 - Motor does not shut off with ignition on
The following repair kits have been released to assist in servicing the Powermaster brake units.
Pump Pressure Ranges
|Special Bleeding Instructions|
|A problem may be encountered in bleeding the PowerMaster if for any reason the pump has not been properly filled with brake fluid. If after any servicer new installation the pump does not circulate fluid after the motor has run for 20 secs, it may be necessary to reprime the pump. In order to reprime the system, the following steps should be performed: