Power master unit info

williambavila

William Avila (The Buick Guy)
Hey guys i am sure this question has been asked several times. But my power master motor keeps running. I have been told Richard Clark has witten some info on this would it be possible for someone to send me a link?
 
I don't know about the literature you are asking about, but if the PM motor runs a lot it typically means the accumulator ball lis leaking off pressure thus requiring frequent recharges. You might want to look over the troubleshooting documentation.
 
Ok so I did the step 4 in the troubleshooting part of the link and the motor continues to run. I have a new accumulator ball and switch on the car. and the fluid drops on the passenger side of the reservoir and does not move on the drivers side. I also cleaned the check valve. ???? new unit????
 
The pass side reservoir is the reservoir that makes the powermaster work. The left side is for the brakes themselves. When the motor runs the right side will drop and as you pump the pedal it will fill back up until the motor starts again.
 
Which pressure switch do you have on the PM, the gray or black one?

pressure-switch.jpg
 
I am glad you asked. I have a grey one and a new one I just bought from kirbans as well as a brand new accumulator bowl. the problem started a few months back i noticed the pump stayed on longer than usual. so I did a bit of research and it lead me to the accumulator and the switch. after replacing both i still have the same issue but the damn thing wont stop running. I can recite the damn instructions in 15 different languages forward and reverse its a pain in my a$$$. what would you recommend. i have the money for a new unit,or vacuume setup? 5 gallons of toluene and a match? a guardrail at 150? :mad:
 
Well, you are covered with the switch and ball, I guess. :)

It really sounds like there is an internal leak or a pressure problem, especially if the pump runs a ton without brake application. You can't really determine for sure unless you have a pressure tester kit. The pump should shut off when the pressure reaches around 610psi (don't quote me on that) or so. If you are not making it there, the pump may not be generating enough output to get to a level where the pump is allowed to shut off. If you have a good switch, accumulator, and you see no external leaks then it can't be much else. It could also be shorted wiring energizing the pump at all times, but I am still leaning toward a weak pump.

If it does end up being an internal leak, it involves a rebuild kit which I do not think is available anymore. Bottom line is you are either not building enough pressure because of a weak motor or you are leaking it off.

You already have some cash in the system if you recently bought the ball and switch. If it were me, I'd probably switch to vacuum or hydro, but you might be able to find just the motor for cheap to pair with your new accumulator. The accumulator doesn't like to sit around, so it doesn't make a lot of sense to buy a whole new PM and shelve a spare ball.
 
Stop dumping money into it and convert it over to a vacume setup, you will be much safer in the long run. PM me I can hook you up with all the right stuff.
 
I've got the original GM tool to check the pressure. If you were local I could check it for you. Could be a weak pump. You can still buy the motor/pump brand new... for $300 ouch.
 
Ok so I did the step 4 in the troubleshooting part of the link and the motor continues to run. I have a new accumulator ball and switch on the car. and the fluid drops on the passenger side of the reservoir and does not move on the drivers side. I also cleaned the check valve. ???? new unit????
So did you put the check valve back in the spring with the poppet. Make sure it sits in the groove
So it can make the proper seal. After that did you have the cover off the resivior when you turned the car on? If so do it and have a bottle of brake fluid in hand to pour in if gets sucked down the motor. Top it off at about 1 1/2 inches from the bottom and put the cover back on. At least this is what happened to me last year when my motor kept running after I took everything
Apart.
 
If the motor will not shut off, there are only 2 things wrong and it could be either or both.
1 - motor isn't putting out pressure
2 - internal leak

Look into the p/s of the bowl that drops when the motor runs and see if fluid is returning from the rear port. If so = internal leak.

Otherwise it's the motor.
 
Ok guys I got the brake issue fixed. I had the grey switch go bad at first. Then I thought the bowl was bad. so I spent 179 on one of those and no fix. Then I found a leaky perportioning valve and fixed that.So after tons of research and contemplation I decided to swap it to vacuum brakes. I finished it this afternoon and it works much better. No brake light,no hard pedal,no whining pump/motor,Just some great brakes. So if anyone needs some bowls that work and a switch let me know
 
Well, that's certainly one way to fix a malfunctioning PM system. :) I'm glad your new ones work since stopping is a very valuable feature on these cars.
 
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