Power Master Brake Light Stays On

[MRP78]

I'm trying to troubleshoot a Powermaster system. The car has sat for a little while. When it's first cranked up the brake light stays on. I checked the brake fluid and it was good in the reservoir closest to the fender but very low on the side toward the engine. I added some brake fluid, cranked it back up and the light went off for a while but then came back on without touching the brakes. The pedal travel seems normal and stopping power is adequate. I turned off the car and then the fluid from the master cylinder overflowed. I pulled the cap off and the one reservoir that was very low before was milky and seemed to be full of air. I've looked at some troubleshooting diagrams on gnttype and other sites but am still not certain where to start.

 

[BILL HAINES]

THE ONE SIDE WILL ALWAYS BE LOWER WHEN SYSTEM IS PRIMED OR RUNNING.. NEVER FILL IT TO THE TOP,OR CHANCES ARE AFTER BRAKE IS PUMPED A FEW TIMES FLUID WILL OVERFLOW..DO A SEARCH ON HERE AND THERE WILL BE A FLOW CHART THAT WILL HELP YOU..

 

[ravege]

The pedal travel seems normal and stopping power is adequate.
When my Powermaster light went on, this statement was true for about 4 pedal pumps, then I nearly took out a UPS drop off center. Be careful.

 

[we4Mateo]

Be careful and don't drive the car until it's fixed; or switch to vacuum.

 

[MRP78]

Is there a most likely cause? Low fluid, leak in a line or wheel cylinder, bad proportioning valve, accumulator, brake switch, or ?

 

[TurboTGuy]

Sounds like an accumulator gone bad.

The fluid will always be milky after the brakes have been pumped, it clears up in a few minutes after the car is turned off.

As stated above, lots of info in the Brakes, Suspensions, Tires and Wheels Forum.

Start here:
http://turbobuick.com/forums/threads/powermaster-brakes-diagnostic-information.362564/#post-2890528

 

[ravege]

In my case I believe the switch stuck on and ran the motor continuously until it died. There was a serious bad smell when I lifted the hood. Fuse was also blown, not certain where in the sequence that happened.

 

[we4Mateo]

In my case I believe the switch stuck on and ran the motor continuously until it died. There was a serious bad smell when I lifted the hood. Fuse was also blown, not certain where in the sequence that happened.

Definite possibility.

 

[Oakmtnbody]

Definite possibility.

My 86' T-Type does the same thing when you first crank it it but the lamp goes off the first time the pedal is mashed and does not come on again.

 

[we4Mateo]

My 86' T-Type does the same thing when you first crank it it but the lamp goes off the first time the pedal is mashed and does not come on again.

Brake light on with a powermaster, even if it stays off after a bit, is not good and should be addressed. Your problem may not be a timely one but it's still an issue and anything with brakes, especially the powermaster, needs to be addressed before you get hurt or hurt someone else. Just my .02.