86' Grand National PowerMaster Brake Unit, lite ON when applying brakes

Grannie86

New Member
Mar 2, 2019
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Deptford, NJ
Yes, reading up on Powermaster Brake Unit. The brake switch has been changed color ( Gray ) but did notice accumulator is solid black ( Kirban site States this is orginal to powermaster ) I have read if lite comes ON when applying the brake is to Replace out accumulator. I checked on Ebay there is a New Accumulator made in Germany for around $170 and slightly larger then stock. Trying to find out procedure Steps, on How to replace accumulator and do it Safetly? and have brakes when done. Any thoughts would be a Big Help Thanks
 

silver/black

Member
Mar 28, 2007
67
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8
best to change to vacuum or hydro ....even replacement power master is failure waiting to happen. can send in power unit for credit to kirbans...at least used to be able to
 

Grannie86

New Member
Mar 2, 2019
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Deptford, NJ
Just curious,learning about the about the powermaster ie ( Slugmaster ) brake System. I know now , I have old GM problem and read the blogs ect. It has 28k, no service records. I wonder what those GNX owners do about there car's,low mileage and orginal sluhgmaster onboard . Like to try and keep it orginal, if a accumulator and a full service bleed solves the problem Cool. But like you stated if it fails ect. then I will convert to a vacuum setup..Thanks
 

BlackonBlack

Member
Aug 26, 2016
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It's always a race on this forum to see who can suggest you swap out the powermaster first!

I have a low mile car and prefer to keep it original as well. I had your same problem and had good luck swapping out the accumulator. The V2 accumulator with the yellow stamping can be found, but the Cardone Accumulators are said to be more reliable.

It is a very simple swap. Key off, depress brake pedal 10-12 times to depressurize the accumulator. A wrench and something to catch the brake fluid. Screw off, screw on.

Hopefully that solves your problem. Turbo Keith on this site had a similar issue on his T and he may have also swapped out the pressure switch to get his light to clear.

From what I have read, the biggest thing with the power masters is to keep the brake fluid clean. If you let the fluid get brown/ coca cola color, the seals go bad and the PM fails internally. Its best to swap out the brake fluid once per year.

Once you get it squared away and back on the road there is a technique I have subscribed to to prolong the accumulator. After you are done driving, turn the key off and depress the brake pedal 10 times. This discharges the accumulator and keeps the pressure off while it sits.

Good luck, hope you can salvage your PM!
 

626gn

Well-Known Member
Feb 15, 2009
2,189
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Honolulu, Hawaii
It's always a race on this forum to see who can suggest you swap out the powermaster first!

I have a low mile car and prefer to keep it original as well. I had your same problem and had good luck swapping out the accumulator. The V2 accumulator with the yellow stamping can be found, but the Cardone Accumulators are said to be more reliable.

It is a very simple swap. Key off, depress brake pedal 10-12 times to depressurize the accumulator. A wrench and something to catch the brake fluid. Screw off, screw on.

Hopefully that solves your problem. Turbo Keith on this site had a similar issue on his T and he may have also swapped out the pressure switch to get his light to clear.

From what I have read, the biggest thing with the power masters is to keep the brake fluid clean. If you let the fluid get brown/ coca cola color, the seals go bad and the PM fails internally. Its best to swap out the brake fluid once per year.

Once you get it squared away and back on the road there is a technique I have subscribed to to prolong the accumulator. After you are done driving, turn the key off and depress the brake pedal 10 times. This discharges the accumulator and keeps the pressure off while it sits.

Good luck, hope you can salvage your PM!
In addition to this^^^ I would add that 9 times out of 10 the reservoir on the passenger side will be filled to the top (or near it) before you depressurize. This is a sign whomever's been servicing/maintaining the unit before you didn't know how to do it properly. Nearly every mechanic that looked under my hood has told me my brake fluid is low. It's happened so many times I don't even bother to correct them anymore lol. If it is full on the passenger side before depressurizing, it's overfilled and when you start depressurizing, fluid from the accumulator will fill the already overfilled reservoir and it will start leaking out from the cover and make a mess under the hood. You should take some fluid out from the passenger side reservoir before depressurizing.
When refilling be sure to follow the fill indicators in the bowl and use only DOT3. Once a year fluid changes is minimum. Even with proper maintenance though there are no guarantees at this point.
 
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Grannie86

New Member
Mar 2, 2019
15
1
3
60
Deptford, NJ
It's always a race on this forum to see who can suggest you swap out the powermaster first!

I have a low mile car and prefer to keep it original as well. I had your same problem and had good luck swapping out the accumulator. The V2 accumulator with the yellow stamping can be found, but the Cardone Accumulators are said to be more reliable.

It is a very simple swap. Key off, depress brake pedal 10-12 times to depressurize the accumulator. A wrench and something to catch the brake fluid. Screw off, screw on.

Hopefully that solves your problem. Turbo Keith on this site had a similar issue on his T and he may have also swapped out the pressure switch to get his light to clear.

From what I have read, the biggest thing with the power masters is to keep the brake fluid clean. If you let the fluid get brown/ coca cola color, the seals go bad and the PM fails internally. Its best to swap out the brake fluid once per year.

Once you get it squared away and back on the road there is a technique I have subscribed to to prolong the accumulator. After you are done driving, turn the key off and depress the brake pedal 10 times. This discharges the accumulator and keeps the pressure off while it sits.

Good luck, hope you can salvage your PM!
Thanks for your input to my PM situation. Every known technique to save and maintain this old GM problem, can not Wait to resolve this issue and Feel how a PM really Brakes, waiting on mailman to deliver New Accumulator. Go from There
 

TexasT

Texas, Where are you from
Sep 10, 2002
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original is nice, but if you drive the car, you are playing with fire. Many have experienced the loss of braking with no warning. Mine went out with less than 30k miles in the late eighties. It will never go back on my car but is ready to go with the rest of the original stuff I've pulled off over the yrs. the powermaster isn't that great anyway. I went hydroboost and it will stop the car no problem. Vac works too. Really, think it through, original ain't that great under the hood when you rear end another vehicle.
 

Ttype6

Well-Known Member
Aug 17, 2004
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Thanks for your input to my PM situation. Every known technique to save and maintain this old GM problem, can not Wait to resolve this issue and Feel how a PM really Brakes, waiting on mailman to deliver New Accumulator. Go from There
If the light comes on every time you push the brake pedal,it's because there is very little nitrogen charge left in the accumulator.The new accumulator will get your Powermaster working correctly. If your booster is leaking back into the passenger side reservoir,you will see the fluid level rise as it sits.Take note of the level when you turn the car off and come back 1 or 2 hours later to see if it rises. If it has a bad enough leak in this area,the pump will come on without depressing the pedal if you leave the key on. There is an acceptable amount of leaking,but if the pump doesn't come on after 15 minutes of inactivity,it's acceptable. If you get a bad enough leak in this area,Kirbans sells the 2 appropriate O-rings to repair this.
 

Grannie86

New Member
Mar 2, 2019
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Deptford, NJ
Thanks for your input. Just ordered New Accumulator from Kirban . Just learning about the PM problems of the Grand National ect.. and other comments to remove entire PM System with a vacuum setup. But like to experience how a PM system feels for the first time, did drive her home with this problem after purchase. Seller will Honor new accumulator, Thx again for your advise
 

Ttype6

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Aug 17, 2004
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Flint,Michigan
Thanks for your input. Just ordered New Accumulator from Kirban . Just learning about the PM problems of the Grand National ect.. and other comments to remove entire PM System with a vacuum setup. But like to experience how a PM system feels for the first time, did drive her home with this problem after purchase. Seller will Honor new accumulator, Thx again for your advise
Did you have good power assist every time you hit the brakes? If so,it will probably feel the same with the new accumulator,but the light won't come on because the fluid pressure won't have an opportunity to drop to the point that the pressure switch gets triggered to turn the light on. The pressure switch does 2 things as the pressure falls. The first thing it does is turn the pump on. If the pump doesn't come on or the charge in the accumulator is too low,the pressure will fall lower and the second switch in the pressure switch will be triggered to turn the light on. As the nitrogen charge,in your old accumulator,leaks more and more,you will get some momentary pedal firmness because the pressure will drop so fast upon each depression of the brake pedal that the pump can't compensate for it fast enough. The reason for this phenomenon is because fluids don't compress.
 

Grannie86

New Member
Mar 2, 2019
15
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60
Deptford, NJ
Thanks Ttype6 for your reply. Seems you have the knowledge on PM brake systems. Curious from yourself, reading the blogs on bleeding procedures (What procedures ?). Like to gravity bleed the front/back brakes like the old vac systems. But confused from comments from years ago on what to do? My new accumulator will be in next week mail, sipon old brake fluid from reservoir first/clean residue, add to correct level. Like to then clear-out old brake fluid thru each brake line, gravity bleed one at a time to clear old brake fluid thru each brake caliper, also keep eye to add fluid to correct level at reservoir. Not sure if this work's or not with PM . Any suggestion would be helpful
 

Reapersgbodys

Active Member
Apr 25, 2017
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I can just tell you my story on my Powerpuker, has the same problem, spent the money for a new accumulator, (bad idea) went thru all the testing trees and that’s what it reverted too, Poof, got brakes back!!! Then lasted for all of 650 miles, the wife and I were on a 450 mile round trip ride to see my dad, 200 miles or so in, Powerpuker puked AGAIN, it was the longest most stressful 250 miles home I have ever had, and my back and hip were sore for 2 days from the hard ass pedal, $170 down the drain, wasn’t too happy as I could have spent another $80 and purchased the vacuum conversion kit. Needless to say, FINALLY got her into the garage and that is where she stayed until Vacuum conversion kit came, Keeping it “original” as so many want no longer became an issue when my family’s safety came into play, GM produced a piece of junk, knew they were junk, that’s why there weren’t too many models produced with the Powerpuker, Vacuum brakes have been around for how long??? And flat out work, will never put a Powerpuker back on my car to keep it “original”, they are just a failure waiting to happen at the most inopertune time .
 
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Ttype6

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Aug 17, 2004
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Thanks Ttype6 for your reply. Seems you have the knowledge on PM brake systems. Curious from yourself, reading the blogs on bleeding procedures (What procedures ?). Like to gravity bleed the front/back brakes like the old vac systems. But confused from comments from years ago on what to do? My new accumulator will be in next week mail, sipon old brake fluid from reservoir first/clean residue, add to correct level. Like to then clear-out old brake fluid thru each brake line, gravity bleed one at a time to clear old brake fluid thru each brake caliper, also keep eye to add fluid to correct level at reservoir. Not sure if this work's or not with PM . Any suggestion would be helpful
Yes,it will gravity bleed. Just do what your thinking of doing each on at a time until clear/clean.
 

Grannie86

New Member
Mar 2, 2019
15
1
3
60
Deptford, NJ
I can just tell you my story on my Powerpuker, has the same problem, spent the money for a new accumulator, (bad idea) went thru all the testing trees and that’s what it reverted too, Poof, got brakes back!!! Then lasted for all of 650 miles, the wife and I were on a 450 mile round trip ride to see my dad, 200 miles or so in, Powerpuker puked AGAIN, it was the longest most stressful 250 miles home I have ever had, and my back and hip were sore for 2 days from the hard ass pedal, $170 down the drain, wasn’t too happy as I could have spent another $80 and purchased the vacuum conversion kit. Needless to say, FINALLY got her into the garage and that is where she stayed until Vacuum conversion kit came, Keeping it “original” as so many want no longer became an issue when my family’s safety came into play, GM produced a piece of junk, knew they were junk, that’s why there weren’t too many models produced with the Powerpuker, Vacuum brakes have been around for how long??? And flat out work, will never put a Powerpuker back on my car to keep it “original”, they are just a failure waiting to happen at the most inopertune time .
Sorry to Hear that, even with Family aboard ect.. I drove my newly Purchased '86 GN from Milford,CT to South Jersey last Week, with this problem. I did research the PM situation vs. Vacuum setup. Old owner will Honor New Accumulator, due in this Monday (Kirban $209 ) I will give it a Total Break flush ect.. I know what most people have Stated about the SlugMaster, but I am so curious and want to feel the Difference, Go from There and Get the car Blessed
 

87WE4!!

Active Member
Jul 2, 2018
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Not that you asked for it but my advice would be to replace your powermaster with vacuum brakes or hydro boost (if u got hydro boost money) and keep your powermaster system. Clean and wrap it up nice just Incase you ever decide to make your car a show car or you ever want your powermaster setup back the option of bench fixing your powermaster system will always be there. But for now while you’re having fun with your car I would definitely recommend you buying a conversation kit from earl brown they are very cheap and the conversion is completely reversible. And trust me someone would buy that vacuum conversion kit the minute you list it. So go vacuum but don’t sell the powermaster would be my advice.

Either way please be safe.
 

Ttype6

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Aug 17, 2004
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Go from There and Get the car Blessed
Among the many things that happened when you accepted GOD's gift of salvation was that you became a King and a Priest. You can proclaim the protective blood of Jesus over anything you own or anyone you know and or love. We believe and therefore speak. Use the most powerful tool that you received,your mouth.
 

Grannie86

New Member
Mar 2, 2019
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Deptford, NJ
Thanks for the Advise, being a New '86 GN Owner, I taken upon myself to troubleshoot the problem myself. Went to two brake places, they finally could not Help/ and I See Why. Found a site called Kirban , tech advised ect.., and ordered a New Accumulator(came in Monday), fresh Dot # 3. Wow SlugMaster performs has Designed. But I will consider your suggestion of vacuum conversion. Rite now GN needs other attention's, tie-rods(front-end alignment), new tires, bit wavy on suspension ? Will Power On THx
 

626gn

Well-Known Member
Feb 15, 2009
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Honolulu, Hawaii
Yeah, your corner brake shop won't be of much help with this system. Gotta be willing to maintain and troubleshoot it yourself (like you just did) or swap it out to a more conventional system and move on. Glad you got it figured out.
 
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