Powemaster Failure??

[Hognose]

A week or so ago my brake light was coming on and off. Now the lght hasn't come on, but occasionally the PM goes out, the next minute it works fine. When it goes out the pedal is rock hard.

What part of the PM is failing and ideas? Thanks

Matthew

 

[SVORay]

I'm pretty sure this link has a place where it helps you diagnose PM problems.

Turbo Buick Technical Articles and Resources (Technical Archives)

 

[zeus87gn]

My money is on the accumulator ball. It's a common failure item on the P/M.
Same thing happened to mine a number of years ago.
Run the diagnostics procedure from the brakes page at GNTType.org to be sure.

 

[Hognose]

Thanks, Hopefully I can get it figured out. I have a working used unit coming in so I can swap parts on.

 

[IawoBill]

Mine just stopped working in my '86 GN too. The reservoir looks full, all cavities. The brake light stays on - all the time. The fluid looks nice and clean (no hint of black crud) and no external leaks. I do not hear the motor running at all but have not made it through all of the diagnostics.
I want to learn something, so I have ordered an accumulator and motor EH. I was wondering about where to purchase the master cylinder seal kit - Partsamerica, Karps or MBM? Who do you think has the most complete kit? Do I even mess with the master cylinder? The car has 94K miles on it
Thanks,
Bill

 

[zeus87gn]

Thanks, Hopefully I can get it figured out. I have a working used unit coming in so I can swap parts on.

If I may offer a word of advice...

The used parts are good for diagnosis, but don't keep them on the car for long. Replace them with NEW parts. These are your brakes, they need to be ready to save your life on demand. Your brakes are no place to skimp out.

If it helps, that light on your dash is coming on because you either have low pressure in the accumulator ball or you have your parking brake on. With the hard pedal happening, you have the low pressure issue to deal with. Either your motor isn't keeping up or your acc ball is dying. Run those diagnostics and you can save some time before you have to turn the first wrench.

 

[zeus87gn]

Mine just stopped working in my '86 GN too. The reservoir looks full, all cavities. The brake light stays on - all the time. The fluid looks nice and clean (no hint of black crud) and no external leaks. I do not hear the motor running at all but have not made it through all of the diagnostics.
I want to learn something, so I have ordered an accumulator and motor EH. I was wondering about where to purchase the master cylinder seal kit - Partsamerica, Karps or MBM? Who do you think has the most complete kit? Do I even mess with the master cylinder? The car has 94K miles on it
Thanks,
Bill

If your fluid looks good, you are in better shape than most. If the motor isn't running at all while doing the diagnostics procedure, check you 30A fuse. If it is blown, replace it and continue with your diagnostics. It blew for a reason and you have to find out why.

The rebuild kits can be had, I have seen them here Welcome to Karps Brake Service only kind of pricy. You will probably have to look around. I don't know if GBodyParts has them or not. I am keeping my eyes open for a board member who is willing to part with a spare kit.

The rebuild kit is to rebuild the master cylinder portion of the P/M only. The Acc ball and the pump/motor can't be rebuilt...only replaced. Follow the kit directions to a T. Use denatured alcohol for parts cleaning. Lube the orings with brake fluid on assembly.

 

[IawoBill]

So, after following the diagnostics, I still was having trouble. I got the exisitng in the car unit to run once then nothing. I would connect and disconnect the connector and could hear the relay opening and closing, but still no running motor. I bought a brand new motor (and everything else) and decided to give it a test. Guess what - it didn't work either. Just the relay on the new motor. I ended up grounding the powermaster motor that is still in the car externally. Got a spark and it started working. I started moving the connector at the motor some more and I could get it to run. I have traced my whole problem to the connector at the motor. It's the ground line that runs to terminal A. Fortunately, it is in the harness. I have not seen this type of problem with weatherpak connectors before - they are usually very good. Plus this car is so clean that it was hard to believe. I will get a weatherpak kit tomorrow to repair the harness. I am glad I have found the problem, plus I now have all of the rebuild parts for future troubleshooting / repair.

 

[NJ Torque]

Mine crapped out too..... converted to vac. brakes, never looked back.

 

[Hognose]

I am not able to be able to do a lot of the tests. However, My brakes have been working fine all week, and then yesterday I got the hard pedal again. It is coming on sporatically. Most of teh time evrything is fine, then out of nowhere the pedal will be rock hard for a couple minutes, then shortly it will go back to normal.

Can the motor work occasioanally? Couls the switch or ball work like this as well?

Thanks.
Matthew

 

[zeus87gn]

I am not able to be able to do a lot of the tests. However, My brakes have been working fine all week, and then yesterday I got the hard pedal again. It is coming on sporatically. Most of teh time evrything is fine, then out of nowhere the pedal will be rock hard for a couple minutes, then shortly it will go back to normal.

Can the motor work occasioanally? Couls the switch or ball work like this as well?

Thanks.
Matthew

Have you read the procedures?
Brake System
Pay attention to the accumulator test and step 2 under corrective actions.

If you have access to either a stopwatch or a timepiece of any kind with a second hand, you can run the diagnostic procedures. Only probem I could forsee not being able to run them is if you are physically disabled and couldn't watch the fluid in the bowl or press the brake pedal to pump the acc ball down. If that is the case, get someone to help. It's really easy.

Swapping parts isn't going to solve anything unless you know what part needs to be changed.

 

[WLDWST]

I am not able to be able to do a lot of the tests. However, My brakes have been working fine all week, and then yesterday I got the hard pedal again. It is coming on sporatically. Most of teh time evrything is fine, then out of nowhere the pedal will be rock hard for a couple minutes, then shortly it will go back to normal.

Can the motor work occasioanally? Couls the switch or ball work like this as well?

Thanks.
Matthew

My Powermaster problem had the identical symtoms. The motor would work as normal for long periods and then would not. Out of frustration and weeks of doing diagnostics and switching out parts to find the problem, I tapped the side of the Powermaster motor one day with a small hammer when it wasn't working. Like you would with a heat soaked starter. It worked. Turns out the motor was fine, but the relay that runs the motor was only working intermittantly. In my case, a new motor from Hank Terry solved the problem immediately.

GM PowerMaster Sales

 

[Hognose]

My Powermaster problem had the identical symtoms. The motor would work as normal for long periods and then would not. Out of frustration and weeks of doing diagnostics and switching out parts to find the problem, I tapped the side of the Powermaster motor one day with a small hammer when it wasn't working. Like you would with a heat soaked starter. It worked. Turns out the motor was fine, but the relay that runs the motor was only working intermittantly. In my case, a new motor from Hank Terry solved the problem immediately.

GM PowerMaster Sales

Thanks, that great info. I just bought a working PM I may just swap the whole thing out.

However, I just did dome of the tests. First thing I noticed is that my brake light does not come on when I start the car or when I turn the key on. On the first test is to count how long it take s to go off. My brake light has not come on at all when I am getting the rock hard pedal. I know the light works because it comes on when I depress the emergenccy brake. Is this a problem?

The unit will not cycle on it's own after two minutes with the key on, it is after depressurizing the system. Also it only takes 10 sec to shut off after turning the key on also.


Thanks guys for your help.

Matthew

 

[zeus87gn]

The unit will not cycle on it's own after two minutes with the key on, it is after depressurizing the system. Also it only takes 10 sec to shut off after turning the key on also.


Thanks guys for your help.

Matthew

There is your answer right there. Your accumulator is dying. Your hard pedal is a classic symptom. Your time to shutoff is good, but a little too long. Replace the acc ball and that time should be cut almost in half once you get the air out of the new ball.

I think the light issue is a problem in the electrical harnes. Can't come up with a good explanation other than that. My light didn't work either when my Acc ball went.

 

[Hognose]

There is your answer right there. Your accumulator is dying. Your hard pedal is a classic symptom. Your time to shutoff is good, but a little too long. Replace the acc ball and that time should be cut almost in half once you get the air out of the new ball.

I think the light issue is a problem in the electrical harnes. Can't come up with a good explanation other than that. My light didn't work either when my Acc ball went.

How do you get the air out of the ACC Ball? Just bleeding the brakes? Should you bleed them with the key on so the motor still putting pressure on the system?

Thanks
Matthew

 

[zeus87gn]

How do you get the air out of the ACC Ball? Just bleeding the brakes? Should you bleed them with the key on so the motor still putting pressure on the system?

Thanks
Matthew

Cycle the accumulator a couple of times until you don't get any air out on pump down.

Cycle => pump down with 10 pedal pumps as you have already done...turn on key to start P/M motor and wait until the motor stops. Turn off key and pump down again. Look for the air to come back into the p/s of the bowl when you pump down, the fluid may get frothy in appearance. If you get it, wait until it clears up before continuing...usually just a few minutes. If it doesn't clear up, you need new fluid in your system.

You should not have to bleed at the wheels after doing this. If you do experience a soft pedal when you are done, then you will need to. There is a chance that air can get into the mastercylinder, but I haven't had the problem. If you do, I do not recommend doing it with pressure in the acc, others do. It pumps up to over 600psi. Do you really want to release that with a bleeder valve? The pedal will be quite firm but you can do it.

Good luck

 

[Hognose]

Ok, I know I am probably becoming a PITA but when pumping up my brakes with the key off, I have brake fluid overfloing from the resivor. I guess I have too much in there. But when do I know if it is to low on the pass side?

I have had this car for over three years and this is the first time I have had any PM issues. So I am definately on a learning curve here! LOL

Thanks again.
Matthew

 

[87TTypeKid]

A curious question to any who may know-

I just replaced my accumulator, and with the reservoir full, it seems as if slowly but surely over time the unit has to re-pressurize more frequently than it used to. Right when I replaced it, you could get 6-7 pumps out of the pedal before it re-pressurized, and now its down to 3-4 maybe, and it sometimes has to pressurize when I turn the car on (whereas I dont really recall this happening right after the installation)...

Any ideas? The brake warning light is off and the brakes work just fine...just concerned a little bit. Thanks.

Oh yeah, powermaster sucks...too expensive to maintain :-P

 

[zeus87gn]

Ok, I know I am probably becoming a PITA but when pumping up my brakes with the key off, I have brake fluid overfloing from the resivor. I guess I have too much in there. But when do I know if it is to low on the pass side?

With the key off, you are pumping your acc ball down (depressurizing) and the fluid is coming out into the p/s bowl with every stroke of the pedal. Once it is completely pumped down, you should have a firm pedal and the p/s of the bowl should be at the top of the full mark. When you turn on the key, the motor will pump the acc ball back up and refill it with about half of the fluid in the p/s of the bowl. Once it does this, leave the fluid at this 'about half full' level. This is correct for the P/M.

I have had this car for over three years and this is the first time I have had any PM issues. So I am definately on a learning curve here! LOL

Thanks again.
Matthew

Don't feel bad, so are a LOT of others here. Just keep in mind, the P/M isn't like any other braking system you have ever dealt with. It is a tiger all it's own, and yet simple as a housecat. You just have to know how to treat it.

 

[zeus87gn]

A curious question to any who may know-

I just replaced my accumulator, and with the reservoir full, it seems as if slowly but surely over time the unit has to re-pressurize more frequently than it used to. Right when I replaced it, you could get 6-7 pumps out of the pedal before it re-pressurized, and now its down to 3-4 maybe, and it sometimes has to pressurize when I turn the car on (whereas I dont really recall this happening right after the installation)...

Any ideas? The brake warning light is off and the brakes work just fine...just concerned a little bit. Thanks.

Did you cycle it to remove the air when you installed it?
You may have a slight internal leak. Run the leakdown test.
A link is above if you don't know what it is.
See my above post for correct bowl level.