Powermaster support thread!

[Alky V6]

good dough??-------not at all------like most of what i do in my shop i do it for fun and to help other TR owners----------i seriously doubt a survey would point to the TR as a brake trap like you suggest--------i really believe that data like that would trigger a safety recall of rather large consequences---------and those high numbers of repairs you have experienced would be almost non existant if the owners would have simply changed their brake fluid occasionally--------as for all those units you are removing????------do you want to sell them???............RC

Did you say safety recall? Pressure switches maybe?
Seriously. How many owners do you think will keep up the maintenance on their PM?
Most vehicles can go from cradle to grave with the same brake system with little maintenance done to them. Not the PM.
The one customer that had me change out the PM unit before failure wanted it back so he could sell the car with the original PM in a box. The others go to scrap. I'm with GM on this one. The PM needs to fade away into history as quickly as possible.

 

[Alky V6]

as for major brake failures I assume that you don't work on early 90's ABS units????--------from what i have seen the failure rate among them is endemic RC

Ahhh good. So the PM has some company. I guess those owners didn't do the maintenance on their brake system monthly either. Makes me feel all warm and safe inside.

 

[Phoff]

Most cars DO NOT go from the cradle to the grave without doing some major work to the brake system....these cars are well over 20 years old now....GM did not build these cars to last much more than 10 years and that includes the Power Master.... most GN owners still use the Power Master brake system without a problem...also you should check your brake light when you start the car to make sure that the bulb has not gone out....alot of people who said the brake light never came on when they had a problem either had a bad bulb or dash wiring...


Pete

 

[Bent6]

How's this for a "support" thread?

Richard is correct about everything he has stated concerning the PM although I will have to respectfully disagree about relieving the pressure for prolonged periods of storage. The PM will give warning signs and it will live a long life IF maintained properly. The problem is that most people never give their braking system a second thought until it lays down on them. The PM does require maintenace as Richard states but most people either don't know this, don't care, or are just too lazy to do it.

I will agree with others that although it will stop if the PM fails it takes considerable pedal pressure ie- both feet and your back to haul it down from speed and with a good deal more DISTANCE which can spell disaster in an emergency situation. As a hard core racer, I wouldn't run a PM on an all out race car but would on a primarily street/occasional track car.

The PM got a bad rep in the 80s because it is different and not many knew how to care for it. I think this is the reason GM wants to put it in the past - not because it's a bad system but because it leaves too many grey areas and potentials for failure due to improper/non-existent maintenance. I have three street TRs two of which I have owned since new - all have their original PMs - only thing I've ever done to any of them is change to the grey pressure switch, replaced the accumulator on two of them, and kept the fluid clean. I do however always watch for the "signs" of problems ......FWIW.

 

[Alky V6]

Most cars DO NOT go from the cradle to the grave without doing some major work to the brake system....these cars are well over 20 years old now....GM did not build these cars to last much more than 10 years and that includes the Power Master.... most GN owners still use the Power Master brake system without a problem...also you should check your brake light when you start the car to make sure that the bulb has not gone out....alot of people who said the brake light never came on when they had a problem either had a bad bulb or dash wiring...


Pete

When I was referring to major brake work, I meant brake master and booster work. A lot of things can be packaged into 'major brake work'. Believe me, I would like to sell more brake master cylinders and boosters, but it just doesn't seem to be as big a problem with other models of vehicles as it is with the TRs. The vast majority of my TR customers have their story about the PM. Some people going through the PM experience more than once. Very rarely will an owner tell me that the PM is completely original. We try to ask about the PM history when we work on a TR.

Anyone who elects to continue using the PM should keep others from driving the car or make sure they are capable of handling an emergency situation with the brakes. I don't feel women would handle it well.

 

[A2000RICH]

When I was referring to major brake work, I meant brake master and booster work. A lot of things can be packaged into 'major brake work'. Believe me, I would like to sell more brake master cylinders and boosters, but it just doesn't seem to be as big a problem with other models of vehicles as it is with the TRs. The vast majority of my TR customers have their story about the PM. Some people going through the PM experience more than once. Very rarely will an owner tell me that the PM is completely original. We try to ask about the PM history when we work on a TR.

Anyone who elects to continue using the PM should keep others from driving the car or make sure they are capable of handling an emergency situation with the brakes. I don't feel women would handle it well.

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

 

[Bent6]

--------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

I've never thought about it like that therefore I stand corrected. While I've been around these cars since they came out in 1986 and I do like to think I know a little more than the average joe, I don't pretend to know it all about everything like some people on here . I just always a$$sumed that relieving the pressure would take the strain off the accumulator and pressure switch when the car is going to sit for prolonged periods of time such as 6mos to a year. Good information Richard!

 

[Ross L]

RC,thanks for all the great info! What would cause the PM motor to run 1-2 seconds each time the brake is touched? No real visible leaks at the switch or ball. I'm guessing an internal leak or contaminated fluid,,,,, just guessing I would love one of thise rebuild kits. To be honest. I bought the Zone lifetime unit years ago and robbed the switch and ball to put on my unit. Is it fair to put the ball/switch back on the new unit and return it for a new one(there-by getting a new switch and ball,,,, again). It was a lifetime warrenty:biggrin:
Ross

 

[aminga]

RC,thanks for all the great info! What would cause the PM motor to run 1-2 seconds each time the brake is touched? No real visible leaks at the switch or ball. I'm guessing an internal leak or contaminated fluid,,,,, just guessing I would love one of thise rebuild kits. To be honest. I bought the Zone lifetime unit years ago and robbed the switch and ball to put on my unit. Is it fair to put the ball/switch back on the new unit and return it for a new one(there-by getting a new switch and ball,,,, again). It was a lifetime warrenty:biggrin:
Ross

Usually if it's in need of a rebuild the motor will run intermittently without touching the pedal. If the light is coming on it's more than likley the accumulator.

I have seen a rebuild kit and have an old one somewhere on the shelf in the garage. While it included a piston most of the wear when I did mine years ago was confined to the orings. If you take the rings out of it and go to the store with the rings in hand I'll bet you can match them up. Be sure to get ones rated for service in brake fluid. Other than that it rebuilds just like a plain old master cylinder.

 

[GNX243]

Brake Fluid

Ever since RC mentioned maintenance as a contributor to the failure of my PM, I have been changing the fluid yearly with DOT 3 (because that is what was in there originally). I noticed that in the brake forum some were using DOT 4. Should I be using DOT 3 or 4 as the replacement? Your comments are appreciated.

 

[A2000RICH]

Ever since RC mentioned maintenance as a contributor to the failure of my PM, I have been changing the fluid yearly with DOT 3 (because that is what was in there originally). I noticed that in the brake forum some were using DOT 4. Should I be using DOT 3 or 4 as the replacement? Your comments are appreciated.

three or four is ok------don't use 5----------watch out for buying o rings----i agree that its the largest "O" rings that are the most usual internal failure---BUT they MUST be EPDM to be compatible with dot 3&4 brake fluid--------send me an e-mail and i will send you a set of the proper kind---------most common reason for motor running every time pedal is applied is low accumulator pressure-------the accumulator is just that-it accumulates a supply of high pressure fluid so the pump doesn't have to run everytime the pedal is applied------the pressure and volume of the accumulator is designed to handle about 2-3 normal applies before the motor has to run again-----as they age they lose nitrogen pressure like an old tire ------remember the motor has only an intermittent rating and needs lots of "OFF" time to cool down between runs---------BUT there are other causes as well-------if your brakes are not adjusted correctly excessive movement can create a need for more fluid displacement which in turn uses more fluid capacity each time--------another is if your particular pressure switch has a lower than normal setting-----an internal leak around the power piston can also require a abnormal amount of apply fluid------a switch that shuts off at too low a pressure leaves less fluid capacity--------i have seen them vary by as much as 100 lbs-------there is a small adjustment on the switch------peel up the small dab of black silicone and there is a small screw underneath that sets the cutoff point----- WORD OF CAUTION--------DO NOT DO THIS IF YOU HAVE NO WAY TO MEASURE THE PRESSURE TO BEGIN WITH---------750 psi is a good range--------don't forget to replace the silicone or the switch will fail from moisture retention---------motor running too much can also come from a leaking check valve that eventually seats at a low pressure and doesnt cause total loss of fluid--------later i will expalin how to check for this-----------busy gotta go.........RC

 

[aminga]

So for reference my dad has had to replace 2 power brake boosters in his 98 Chevy Truck with a vacuum booster.

 

[turbonut85]

This has been a very informative thread.....minus the bickering of course. My 85 came with the PM....must have been a late year production....It has had it's share of issues but overall has worked good. As with ANY car part/electronics/you name it....the people that "hate" the particular item (the PM in this case) are usually the type who want something to just "work like it should" and don't take the time to research and maintain things. They usually just bitch and then throw it away. I'm guilty of this, I think all of us are at some point. Just imagine what the TR in general would be today if all of the people who bought them tossed them to the junkyard because they didn't run right EVERY time they started them. Don't hate the PM just because you don't understand it. That being said, EVERYONE is entitled to thier OWN opinion and are FREE to express it. Just don't beat each other down because your opinion differs from theirs. If people want to complain about someone else's opinion, do it in the lounge forum...lets keep this fourm "technical" like it says. If you don't like the PM, tell us and tell us why....then leave it alone unless you have any "technical" tips for the people who are trying to learn about them.

 

[turboc87gn]

http://www.turbobuick.com/forums/br...ompany-hydroboost-newfangled-powermaster.html Check my thread lemme know whatcha think...

 

[Phoff]

Buick started to install Powermasters in the Turbo Regals in March of 1985....a little more than mid year for the 1985 models.

Pete

 

["Turbo-T"]

So why was the hydroboost done away with for a PM? Doesn't make sense.

 

[87GNSteve]

So why was the hydroboost done away with for a PM? Doesn't make sense.

This might start another Sh!t storm but when the hydroboost lets go you loose braking AND steering!
Ask me how i know.....




Ok I'll Tell ya 1990, I had a 1985 T type w/ 16 K miles and the thing suddnely went kaput nearly crashed into a parked car cause of the double power assist loss
Needed a wrecker to move the car period.
Oh yeah it sprayed power steering fluid all over the engine comparment and soaked the hood liner too.
$225 1990 dollars to get a replacement unit.

 

[Alky V6]

So why was the hydroboost done away with for a PM? Doesn't make sense.

A failed experiment towards braking systems advancement. Sometimes when you try to move forward, you're forced to move backwards.

 

[Blown&Injected]

So what happens when the engine stalls and no more vacuum is made?

How about when the cheap one-way vacuum check valve fails and the booster looses vacuum?

How about when the vacuum booster fails?

I have had all that happen to me in the near 30 years of driving behind me.

I had the switch go bad - before the recall and I felt the pedal go from normal to semi-hard. When ya feel semi hard ya find a place to stop and try to see what's up. I kept driving it and it was just like any vacuum system that had a booster or vacuum hose failure.

So it seems the only maintenance is change the fluid - and that is a good idea for ALL brake systems anyway.

HEY RICH-------is the return key busted on your keyboard? I like reading your posts but it is not easy!!!!!!!!

 

[turboc87gn]

The pm may have replaced hydroboost but then one may ask y does my 2006 and 2007 chevy express cargo 2500 both have hydroboost they gotta stop a lot more than the 2 tons that a turbo regal weighs especially when theres 2000 lbs in the back mabye they redesigned the new hydroboosts and feel that they are better than the 80s units mabye the powermaster was used because the trs were unique so gm felt the powermaster was unique and would add to the rarity of the cars idk all i do know is mine has been in the garage 2 summers due to a leaky pm motor and after reading this i dunno if i wanna keep it or not im leaning toward not if im gonna spen $600 then i may as well go with hydroboost instead of an autozone p master....the cheapest motor ive found so far was a nos unit for $260 dunno.....