Power Master Guru...

[DeltaBravo]

I've recently had a power master system failure.

Started out with an accessional brake light coming one when using the brakes, then disappearing after a couple of seconds. Also had a very slight 'feedback' in the brake pedal...almost felt like something was tapping on the brake pedal.

Recently I notice brake fluid leaking from the top of the reservoir on the engine side. I removed the cap and adjust the fluid level using the correct procedures for the power master system....I think I overfilled it on my last brake service.

After adjusting the fluid level and connecting everything, now my brake light is one steady with a very hard pedal. And I can not get the motor to turn on.

I've used the following link for troubleshooting
http://www.gnttype.org/techarea/brakes/PwrMstr.html

Fuse is good, circuitry is good, brake fluid is good. As per the trouble shooting, the motor seems good as well as the pressure switch.
***edit*** I don't know if the motor is good, but the relay in the motor test are good.

So, my question is...if it is the accumulator, then why wouldn't the motor work?

Thanks in advance.

 

[DeltaBravo]

I think it's my motor....what'cha think?

 

[fastblackracing]

The power master brake system is easily mis understood and in my opinion a big POS that buick put on our cars.
They should have engineered a better system and re called every car built and retrofitted them.
I still run one on my car but I am familiar with there operation and the electrical circuits.

With that said the accumulator is simply a storage chamber that holds pressurized fluid until the next brake application is performed, some of the fluid is used up, the chamber pressure drops, the pressure switch closes
[ A and C on the switch ] and this provides the GROUND side for the RELAY COIL that will then energize and complete the circuit to allow power +12vdc to go to the motor armature and at this point the motor should run.

If you have done the testing correctly either the relay coil is not energizing and closing the circuit or if this part is good the motor armature is not getting +12vdc through the relay contact that is now closed.....either from no +12vdc supply voltage or the relay contact is burned/broken......or if this contact is good and closing and has the +12vdc the motor armature is likely bad....either worn out, open windings etc...... also the ground side for the motor has to be good.

The 4 pin connector on the motor part of the power master has 2 functions.
1. 2 of the pins B and D turn the internal relay off and on [controlled by the pressure switch]
2. 2 of the pins A and C provides +12vdc to the motor armature [ pin C ] and the ground side to the armature[pinA]
you can not really test the motor windings do to the fact the internal relay needs to be energized to complete the circuit....so it will look like it passes the pin A and C test [open] but this does not tell you the condition of the motor
since that circuit is open. Now if you apply power to the coil to energize the relay the pin A and C test may tell you something.

Also you need to make sure that the Ground that pin A on the motor 4 pin connector provides is intact. [Not likely an issue]
Ground point is G109 rear of engine compartment right of brke master cylinder.

This is something that if you are not pretty well versed in electrical systems and do not do this type of work on a regular basis it will be easy to be overwhelmed with this power master system.
Sounds like your motor or the internal relay is bad.

And since the cost of a new brake system 600-1000, compared to an accident with your car is pretty reasonable
I would advise you to replace this with a freshly re-manufactored unit or a known good used unit.

 

[hrhoward]

I remember the first time I had problems with the Power Master. It was back in '88 on my first '86. Switch turned into a mini brake fluid geyser. Never liked them and changed them over to conventional as soon as I could.

 

[DeltaBravo]

]With that said the accumulator is simply a storage chamber that holds pressurized fluid until the next brake application is performed, some of the fluid is used up, the chamber pressure drops, the pressure switch closes
[ A and C on the switch ] and this provides the GROUND side for the RELAY COIL that will then energize and complete the circuit to allow power +12vdc to go to the motor armature and at this point the motor should run.[/QUOTE]

With that said the accumulator is simply a storage chamber that holds pressurized fluid until the next brake application is performed, some of the fluid is used up, the chamber pressure drops, the pressure switch closes
[ A and C on the switch ] and this provides the GROUND side for the RELAY COIL that will then energize and complete the circuit to allow power +12vdc to go to the motor armature and at this point the motor should run.
The switch is closed allowing power to the relay...so switch seems good right?

If you have done the testing correctly either the relay coil is not energizing and closing the circuit or if this part is good the motor armature is not getting +12vdc through the relay contact that is now closed.....either from no +12vdc supply voltage or the relay contact is burned/broken......or if this contact is good and closing and has the +12vdc the motor armature is likely bad....either worn out, open windings etc...... also the ground side for the motor has to be good.
All the required power is getting to the relay. How do I check the ground of the motor? just one lead on the motor housing to a good known ground?

The 4 pin connector on the motor part of the power master has 2 functions.
1. 2 of the pins B and D turn the internal relay off and on [controlled by the pressure switch]
2. 2 of the pins A and C provides +12vdc to the motor armature [ pin C ] and the ground side to the armature[pinA]
you can not really test the motor windings do to the fact the internal relay needs to be energized to complete the circuit....so it will look like it passes the pin A and C test [open] but this does not tell you the condition of the motor
since that circuit is open. Now if you apply power to the coil to energize the relay the pin A and C test may tell you something.
All checks seem good. I turned ignition on and got 12 VDC across the motor windings, pins A and C...what does that mean?

Also you need to make sure that the Ground that pin A on the motor 4 pin connector provides is intact. [Not likely an issue]
Ground point is G109 rear of engine compartment right of brke master cylinder.
Check is good.

 

[BEATAV8]

The motor has failed.

If you want to keep the powermaster the best thing to do is rebuild it yourself. And i mean the whole thing...

New pump from cars inc
New master cylinder seals from Karps power brake service
New accumulator and switch from Kirbans

After all that just keep the fluid clean and store the car with the system depressurized (pump it down with key off) and it will last a long long time

 

[DeltaBravo]

The motor has failed.

If you want to keep the powermaster the best thing to do is rebuild it yourself. And i mean the whole thing...

New pump from cars inc
New master cylinder seals from Karps power brake service
New accumulator and switch from Kirbans

After all that just keep the fluid clean and store the car with the system depressurized (pump it down with key off) and it will last a long long time

When you say the motor has failed, is that determined from my power/continuity checks that I posted from 'fastblackracing'?

Greatly appreciate the options on rebuilding myself, however the Kirban power master option is cheaper than sources all the parts and rebuilding myself. Why wouldn't I just order a rebuilt one from Kirbans? Is it because of the motor? As I can tell, the motor from cars inc is actually new not a reman, were as the units offered from Kirbans discloses the motors are rebuilt...

 

[DeltaBravo]

The power master brake system is easily mis understood and in my opinion a big POS that buick put on our cars.
They should have engineered a better system and re called every car built and retrofitted them.
I still run one on my car but I am familiar with there operation and the electrical circuits.

With that said the accumulator is simply a storage chamber that holds pressurized fluid until the next brake application is performed, some of the fluid is used up, the chamber pressure drops, the pressure switch closes
[ A and C on the switch ] and this provides the GROUND side for the RELAY COIL that will then energize and complete the circuit to allow power +12vdc to go to the motor armature and at this point the motor should run.

If you have done the testing correctly either the relay coil is not energizing and closing the circuit or if this part is good the motor armature is not getting +12vdc through the relay contact that is now closed.....either from no +12vdc supply voltage or the relay contact is burned/broken......or if this contact is good and closing and has the +12vdc the motor armature is likely bad....either worn out, open windings etc...... also the ground side for the motor has to be good.

The 4 pin connector on the motor part of the power master has 2 functions.
1. 2 of the pins B and D turn the internal relay off and on [controlled by the pressure switch]
2. 2 of the pins A and C provides +12vdc to the motor armature [ pin C ] and the ground side to the armature[pinA]
you can not really test the motor windings do to the fact the internal relay needs to be energized to complete the circuit....so it will look like it passes the pin A and C test [open] but this does not tell you the condition of the motor
since that circuit is open. Now if you apply power to the coil to energize the relay the pin A and C test may tell you something.

Also you need to make sure that the Ground that pin A on the motor 4 pin connector provides is intact. [Not likely an issue]
Ground point is G109 rear of engine compartment right of brke master cylinder.

This is something that if you are not pretty well versed in electrical systems and do not do this type of work on a regular basis it will be easy to be overwhelmed with this power master system.
Sounds like your motor or the internal relay is bad.

And since the cost of a new brake system 600-1000, compared to an accident with your car is pretty reasonable
I would advise you to replace this with a freshly re-manufactored unit or a known good used unit.

Thanks for the help, I think my motor is bad. All test are pointing to the motor....

Now, I am at a conundrum...convert to Vacuum or replace and keep what I've got.

1. Vacuum...reliable and ultimately cheaper. However, I won't be able to build boost at a stand still, or do my nasty burnouts either.
2. Replace and keep stock...more expensive and will require more TLC. Not as reliable...but I will be able to do nasty burnouts and build boost off the line.

 

[GNRick]

Option 3 hydroboost

 

[czimpel]

Vacuum Conversion by Earl Brown.
http://www.turbobuick.com/threads/vacuum-brake-conversion.438078/#post-3648927

Hydroboost Conversion by turbonut85.
http://www.turbobuick.com/threads/powermaster-to-hydroboost-conversion.307690/

 

[DeltaBravo]

Option 3 hydroboost

RIGHT!..but fill me in please...what are the pro's and con's of that route?

I am leaning towards replacing the motor with a new one and rebuilding the master with new seals. My switch is good...dunno about the accumulator, other than it was working fine until the motor went.

But if I replace the stock unit completely, I think I will go with the Vacuum system from Kirbans.

 

[BEATAV8]

When you say the motor has failed, is that determined from my power/continuity checks that I posted from 'fastblackracing'?

Greatly appreciate the options on rebuilding myself, however the Kirban power master option is cheaper than sources all the parts and rebuilding myself. Why wouldn't I just order a rebuilt one from Kirbans? Is it because of the motor? As I can tell, the motor from cars inc is actually new not a reman, were as the units offered from Kirbans discloses the motors are rebuilt...

You hit the nail on the head... a new motor is going to be the best way to go just because it's 100%. We don't know all the details about what a rebuilt pump and motor assembly has had done to it. It could be a cleaned up used unit that passed some bench test and has some variable amount of life left to it, or it could be 100% rebuilt with all new pumping components, brushes, windings, etc... or anywhere in between. I've never seen one that met the later description....

I think your motor quit based on your description. I think it was leaking internally and having a hard time building enough pressure to shut off. It may have been leaking internally within its own pumping unit, or leaking within the master cylinder booster section seals, or both. Either way It was running a lot, probably running most of the time and finally started running nearly continuously at which point it burned up and quit. During this period of "running a lot" you still have brake boost assist and only occasionally the light will come on after you've hit the pedal a few times and used up what little has been accumulated.

I know cars inc is running low on stock, less than 100 new motors left. And they're looking for someone to do a good job remanufacturing used cores but haven't found anyone yet.

 

[BEATAV8]

Also, I would replace everything together unless the switch is really very new. The motor is too expensive to put an old switch on it.

The aftermarket Hydac accumulators are actually better than the originals. Haven't seen one of those fail yet. If you have one already, its probably good to use.

 

[Steve V]

There's a new book that Kirban sells maybe others as well, that Richard Clark and John Norton wrote together. I have seen the book and if you can't fix it with the book then just send it to Richard. He can rebuild the entire thing and has all the specialized GM equipment. He's vendor on here and I've seen him work on many while I was building my motor at his shop. Top notch guy and top notch job. I don't know what he charges and he maybe able to fix that motor he's had those apart while I was there as well.

 

[Dennis Kirban]

Kirban 2 cents worth:

Lots of options which has been pointed out we sell 4 options actually 5 options. Rite now our biggest seller is vacuum set ups with the pedal to make the switch. Hydroboost we offer two systems....kinda of costly to buy and costly to install as its not a simple 1-2 hour job as chances are unless your lucky enough to find someone that has installed it before it takes time and time is money. It is the way to go if drag racing is your plan and if your engine is modified internally where vacuum is less than ideal for vacuum brakes.

We sell complete rebuilt powermaster units that carry a life time warranty. Cardone has one person specifically that rebuilds them. and has for us for 10 plus years. That is another option. We sell the Norton/Clark book which goes into great detail on how to rebuild the pm unit. Richard Clark has even put together a complete o-ring kit for the internals that we also sell.

Cardone has reproduced the brake bowl which has been bullet proof since we first tested it about 6 years ago. Somewhere running around is a WE4 we sold that has the very first cardone brake bowl on it. It can be frustrating. Not a day goes by that we don;t get a call on brake issues.

Every pm owner dreads the day their brake lit comes on....

denniskirban@yahoo.com

 

[DeltaBravo]

Vacuum Conversion by Earl Brown.
http://www.turbobuick.com/threads/vacuum-brake-conversion.438078/#post-3648927

Hydroboost Conversion by turbonut85.
http://www.turbobuick.com/threads/powermaster-to-hydroboost-conversion.307690/

So...I'm thinking the hydro boost system has both the reliability and the ability to do nasty burnouts and quick launches as well as stopping quicker...right! And the parts are still available and reasonable.

I'm thinking this might be the best option for me. Is there anything I'm missing? Anything that might not be appealing about this set up?

I'm able to get everything by tomorrow and under $300

Sounds good too me...but again, I don't want to get knee deep into something and realize I don't like it.

 

[DeltaBravo]

Kirban 2 cents worth:

Lots of options which has been pointed out we sell 4 options actually 5 options. Rite now our biggest seller is vacuum set ups with the pedal to make the switch. Hydroboost we offer two systems....kinda of costly to buy and costly to install as its not a simple 1-2 hour job as chances are unless your lucky enough to find someone that has installed it before it takes time and time is money. It is the way to go if drag racing is your plan and if your engine is modified internally where vacuum is less than ideal for vacuum brakes.

We sell complete rebuilt powermaster units that carry a life time warranty. Cardone has one person specifically that rebuilds them. and has for us for 10 plus years. That is another option. We sell the Norton/Clark book which goes into great detail on how to rebuild the pm unit. Richard Clark has even put together a complete o-ring kit for the internals that we also sell.

Cardone has reproduced the brake bowl which has been bullet proof since we first tested it about 6 years ago. Somewhere running around is a WE4 we sold that has the very first cardone brake bowl on it. It can be frustrating. Not a day goes by that we don;t get a call on brake issues.

Every pm owner dreads the day their brake lit comes on....

denniskirban@yahoo.com

Hi Denis,

I called you earlier today. Appreciate your time. I'm on the fence...but leaning towards the Hydro boost set up. But why do you say it is expensive? And why would it be any harder to install than the Vacuum boost set up? They both seem pretty straight forward to install. Both require slight modification that are both reversible...

I think the hydro boost will give me the ability to track my car and reliability. As well as parts available anywhere in the U.S.

Damon

 

[DeltaBravo]

Also, I would replace everything together unless the switch is really very new. The motor is too expensive to put an old switch on it.

The aftermarket Hydac accumulators are actually better than the originals. Haven't seen one of those fail yet. If you have one already, its probably good to use.

How do I know it is a Hydac? is that stamp or labeled on it? Can't look now, too dark....and the beer is also too good.

I will check in the morning....still thinking over which direction to go.

Thanks for the help

 

[DeltaBravo]

other than some brake fluid and some extra 'return line' hose...this is very reasonable

 

[GNRick]

The 84 gn hydroboost doesn't have the accumulator to allow for that one extra assisted pedal push in case the engine quits on you. To save money get one off a Chevy Astro van from the junk yard.