Powermaster pump keeps running.....

[daninmich]

I am having an issue where my pump will not stop running. I have that diagnostic service tool and the system is pressurizing to 540 and cycles off at 770. It just keeps cycling between 540 to 770.

When I turn off the ignition it bleeds off and doesn't suddenly drop to at 200psi to zero?

Is it the motor?
A leak?
Accumulator??

 

[626gn]

Had a similar problem few years ago. Replacing the accumulator fixed it. However, it could also be your brake switch or even an internal leak in the pump but the fact that it does cycle off leads me to consider the accumulator or switch as the likely suspect. Most decide not to throw money at their powermonster as the parts are expensive and just convert to vacuum or hydroboost.

 

[TurboDave]

Hmmm, check valve or accumulator.

Sent from my QMV7A tablet via Tapatalk.

 

[TRICKSIXPA]

Mine did that and I had to replace the check valve from another unit I had laying around.

 

[turbo nasty]

The check valve probably just needs a cleaning with a fine scotch brite pad.

 

[Nelson Ramos]

Had the same problem mine kept popping fuses, I converted to hydrobost. Works unbelievable!
I have a New accumulator ball and new switches if needed. Inbox me if interested.

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[gnxparts]

Where is the check valve?

 

[626gn]

Check valve assembly consists of parts 36, 37 & 38 in diagram below. Be sure you discharge the accumulator before working on the system.

 

[Tony N]

The seal in the master cylinder might have failed that will also make the the pump cycle and stay on continuously.

 

[daninmich]

Tony- what is the seal?

626- where do you get the check valve hardware??

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[626gn]

Tony- what is the seal?

626- where do you get the check valve hardware??

Posted from the TurboBuick.Com mobile app

As others have mentioned, cleaning the check valve may be all thats needed. I'd try that first before replacing.

The seal that Tony is referring to is in the powermaster body. If that's the problem you would need a rebuild kit which may be hard to find. Last I heard Karps Brake Service in Cali was selling them but not quite sure if they still do..http://www.karpspb.com/booster.htm

Cleaning the check valve is free. Try that first. The following is a cut & paste from RC explaining the failure rates of various powermaster components:

most of the PM's i have seen with problems have been made worse due to people working on them that don't know how to work on them-------thats where most of the horror stories come from-------owners spend large amounts of money and get worse off due to repairs that are not needed or are done wrong------i probably have 5 or 6 hundred units that i have "picked up" over the last 15 years that were removed that were thought bad--------i keep track of the failures and most times its minor-------naturally the black switch is worst offender but GM recalled that---------only about one in 25 has a bad grey switch-------one in four has a bad or weak accumulator--------one in 15 has a bad motor/pump---------one in 30 has internal seal leaks--------one in three has a leaking check valve---------a large percentage are fine if the check valve is cleaned and the fluid is replaced--------many are discarded due to some idiot overfilling the inner cavity even when it clearly states on the lid to not add fluid without first pumping down the accumulator--------and speaking of pumping the system down to make it last longer-------look at my stats-------one of the largest failure modes is the accumulator and check valve--------there is more strain on the accumulator diaphragm when it is pumped down than when it is pumped up-------when it is pressurized there is equal pressure on both sides of the diaphragm and it is equalized and more centered in the accumulator-------it will last much longer in that condition than when it is relaxed---------accumulator failure is always due to chemical attack (from contaminated fluid) of the diaphragm and adhesive used to hold it in place around the perimeter of the ball--------pressure in the ball also holds the check valve sealed and keeps it formed to the seat-------if it fails to seal then its gonna leak down in a short time anyhow---------i have actually found "bad powermasters" that have been removed from cars for 10 or more years that are still pressurized----------if a unit is in tip top shape it will sit for months or even over the entire winter and not lose pressure-------pumping it down requires the motor to run longer than normal every time you start the car which is not really healthy for it--------part of the achilles heel of the PM is that the motor is not rated for more than intermittent duty--------GM suggests that 15 seconds is tops for testing purposes and this is about how long it takes to pump up a system from start---------i have repaired hundreds of these things for friends and have built special tools and fixtures to test them-------when i get a chance i will post some pics of them and explain how to repair them-------the kits are hard to find but several years ago i had a rubber seal company custom manufacture the parts necessary to fix them-------perhaps someday i will put them together in a kit and offer them.................RC

 

[BMR]

On mine the pump.never stops running and it has no assist. The brake pedal is stupid hard to press. Any ideas for that one? Car has been sitting for years. Last tag was purchased in 2000.

 

[tonysmach]

The check valve is a common problem. The check valve holds the fluid in the accumulator ball. The single reservoir on the master cylinder fills up with brake fluid and then the pump turns on to push into the brake accumulator ball. When the check valve leaks the reservoir fills up and the pump kicks on again. The cycle continues. You can usually tell if the check valve is leaking if you see the single reservoir full with brake fluid when the ignition is not on. I have removed my check valve many many times and cleaned it, added rubber washers, etc. but it eventually goes back to leaking.
Bottom line: We need someone to reproduce a better check value for the PM.

 

[BMR]

The way I am taking it is the pump is going to just be on and off if the check valve is acting up. mine never stops running like it never builds any pressure. I gave it a look today and the entire reservior was full. BUT the car has been sitting for 5 months since i got it and pulled the motor. Plus all the time it sat before i got it.

 

[BMR]

So after a long wait on machine work, mine is running again. I checked the tank with the pump running, and I do not see fluid circulating back into the tank. I removed the feed line to inspect the check valve, but did not see how the vavle was supposed to come out. Any tips?

 

[BMR]

I decided to say F the powermaster, and put vacuum assist on it.