I had my car in storage for 8 years. Got it out of storage last year. I noticed the powermaster pump would run every time the brake pedal was pressed. I just bought a new accumulator and replaced it last week. I added new brake fluid. Turned the ignition on and the pump filled the accumulator. The fluid level in the reservior got lower as the pump ran. Today is the first time I took the car out since I replace the accumulator. I drove around the block and everything was normal. So I went for a cruise. While comming to a stop, the brake light came on. Inside the car I could hear the sound of fluid hissing. Opened the hood, It appeared the pump would fill the accumulator them the reservior would start filling up with fluid when the pump stopped running. It was as if a check valve was not keeping the fluid in the accumulator. I got the car home and let it sit for about an hour. Now the pump and accumulator works normal. Is it possible there was air in the system?
Replaced accumulator. Brake light came on.
- Thread starter RobS
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You may have had air, but if you didn't see any froth fluid I doubt it. Try cycling the acc and see what happens. See my sig for proper procedures.
If I may add, you need to keep a close eye on that P/M. They don't like to sit, they like to be used. You may have just had a seal that needed to re-seat after having not been use in so long (fluid dynamics thing) but you could have other problems.
You may want to eve run a diagnostics check on it.
Find them here: Powermaster Diagnostics
Pay close attention to the time the P/M takes to self cycle.
Let me know if you have questions.
If I may add, you need to keep a close eye on that P/M. They don't like to sit, they like to be used. You may have just had a seal that needed to re-seat after having not been use in so long (fluid dynamics thing) but you could have other problems.
You may want to eve run a diagnostics check on it.
Find them here: Powermaster Diagnostics
Pay close attention to the time the P/M takes to self cycle.
Let me know if you have questions.
I guess I should have removed the reservior cover when the powermaster was acting strange. I could see the fluid level through the plastic. When it was acting strange the pump was running longer than normal. Now the pump runs after the second brake pedal application and stops running after about 6-7 seconds.(I have to time it). Does anyone sell a rebuild kit for these? Complete powermasters are over $500 now.
14 seconds is way to long for it to pump back up.
Do this, after it pumps back up let it sit with the key on and see how long it takes until the motor runs again without any help from you. this is called the internal leak test.
if the time is less than 2 minutes, start saving your money. REbuild kits can be had, but unless you have a full rebuild manual with step by step procedures, don't attempt it. Your brakes are nothing to play with and the P/M is a strange animal.
FWIW, Kirbans deal on a complete rebuild is pretty good. It may cost you that much when you include shipping, but when you take the cost of the individual components into account you could end up spending more. Especially if you need a motor.
Do this, after it pumps back up let it sit with the key on and see how long it takes until the motor runs again without any help from you. this is called the internal leak test.
if the time is less than 2 minutes, start saving your money. REbuild kits can be had, but unless you have a full rebuild manual with step by step procedures, don't attempt it. Your brakes are nothing to play with and the P/M is a strange animal.
FWIW, Kirbans deal on a complete rebuild is pretty good. It may cost you that much when you include shipping, but when you take the cost of the individual components into account you could end up spending more. Especially if you need a motor.
I drove the car to work today and when I got there it started doing the same crap. The thing that is driving me crazy is the fact I bought a new accumulator last week and the powermaster was functing normally until I put the accumulator on. If I buy a whole unit I would have the lifetime warrenty. So now I have a new accumulator and no use for it. AAAAAAAAAAHHHHHHHHH!
One other thing I forgot to mention. When its acting strange, the pedal is harder than normal when you first apply the brake. Then as the pedal moves, it feels normal (soft). I think the o-ring that seperates the pressure side from the brake side is leaking. If the motor sounds weak than its time for a rebuild. Thanks for the help.
One other thing I forgot to mention. When its acting strange, the pedal is harder than normal when you first apply the brake. Then as the pedal moves, it feels normal (soft). I think the o-ring that seperates the pressure side from the brake side is leaking. If the motor sounds weak than its time for a rebuild. Thanks for the help.No no. A spare acc ball is called backup. Always a good thing to have. You can keep it and a wrench in the trunk and change it at a moments notice.I drove the car to work today and when I got there it started doing the same crap. The thing that is driving me crazy is the fact I bought a new accumulator last week and the powermaster was functing normally until I put the accumulator on. If I buy a whole unit I would have the lifetime warrenty. So now I have a new accumulator and no use for it. AAAAAAAAAAHHHHHHHHH!
You pedal is normally hard? That's strange.
The sound of the motor doesn't indicate a leak. The time for self cycle is what does. Also if you see fluid movement (circulation) in the ps of the bowl during either pump up or while you are waiting for self cycle.
You are still describing a weak accumulator. You have replaced it?
Have you timed the self cycle of the P/M? I don't read it.
It is important. It will tell you if you have that internal leak.
Something that may help, if you P/M seals are weak in the first place, a fresh acc ball can (may) put thim to an early grave. It's an unfortunate side effect, but nontheless true. It happened to me.
Zeus, Thanks for all your help. I will start from the beginning. My current powermaster was installed by the dealer back in either 1989 or 1990. In 2006 I got my car out of storage after sitting for 8 years. I changed the fluid in the reservior. The pedal was soft (like normal) but the pump would run every time the pedal was pressed. Fearing a weak accumulator would cause the the pump to run longer, blow a fuse to the pump, then have no brakes. I bought a new accumulator from Kirbans last week. I removed the fluid from the reservior, removed the old accumulator, installed the new accumulator, then filled the reservior with new fluid. The pedal was soft. The pump would run after 2 pedal depressions. I went out for a short cruise(for the first time) and the brake light came on. I pulled over. I noticed the pump was running alot longer than normal and self cycling without any pedal input. I also noticed the hard pedal, move the pedal than soft thing, and a hissing sound inside the car. I drove straight home. Looked on line for any posts similar to mine. After about an hour, I went back outside to check for foamy fluid after the accumulator pressure was released. There was none. I turned the key on, and the powermaster started working normal.(No hissing sound, no self cycling, soft pedal,pump would run 5-6 seconds after 2nd brake apply, 14 seconds to fill accumulator. Maybe it was air? I drove may car to work (2 miles) yesterday. When I got to work, I could hear the hissing sound inside the car again, hard than soft pedal. Drove it home at the end of the day and the brakes worked normal. I think I have a internal seal leak , due to the installation of the new accumulator, that is intermittent. If thats possible. The unit is at least 17 years old so I think its time for a new one. I do have a service manual, thats why I wanted to try to rebuild my current master cylinder. Also I had trouble with autozones lifetime warranty in the past. Thanks again for the help. Rob
No problem. I just hope we can solve the problem.
Ok, did you flush the rest of the system (bleed at the wheels)? If you didn't, there is a real good chance you have introduced some air into the master cylinder. You might need to bench bleed it if bleeding at the wheels doesn't seem to help.
You have said many times that the pedal is soft. Do you mean it feels like a normal pedal in any other car?
Wait, did you release the pressure pumping the pedal or did the system do this on it's own?
It's posible. You did mention that the unit would self cycle without influence. You may have an oring that is trying to re-seat itself. It probably won't last much longer if that's the case. My P/M was giving me similiar symptoms, only it didn't go back to normal. When I tore it down, I found 2 blown orings on the power piston...the main orings that hold the pressure.
There is a place in california call Karps Brakes - Welcome to Karps Brake Service.
I have been told that they have some kits, but have your credit card ready. They are proud of them.
Is you service manual dedicated soley to the P/M?
Or is it for the whole car like a Haynes?
Have you ever rebuilt a master cylinder?
Wow zeus, I didnt think I would generate so many questions after a long post.
No. I used a hose and siphon to remove the fluid in the resivior.
Soft like a normal pedal in any other car.
Yes. I pumped the pedal with the key off until it got hard. Then 5 more pumps.
I think it won't go back to normal. I don't want to take the chance of losing the power assist.
I have a GM chassis service manual. No I have not rebuilt any master cylinders but I did rebuilt my motor. I got an awesome set of tools.:biggrin:
I found a rebuilt unit at pep boys for $350. Its a brand called prior. Not sure if its any good. Rob
No. I used a hose and siphon to remove the fluid in the resivior.
Soft like a normal pedal in any other car.
Yes. I pumped the pedal with the key off until it got hard. Then 5 more pumps.
I think it won't go back to normal. I don't want to take the chance of losing the power assist.
I have a GM chassis service manual. No I have not rebuilt any master cylinders but I did rebuilt my motor. I got an awesome set of tools.:biggrin:
I found a rebuilt unit at pep boys for $350. Its a brand called prior. Not sure if its any good. Rob
Technicalities can make a difference.RobS said:
Ok, you very well could have gotten air in there. You may want to consider bleed the wheels. It will get new fluid in there and get any possible air out.RobS said:
Ok, good - standard pedal. Good to hear that it didn't bleed down by itself.RobS said:
BUT you should time for internal leaks. It will give you a good indication of if you should bother breaking into it.
Good philosophy.RobS said:I think it won't go back to normal. I don't want to take the chance of losing the power assist.
Ok SpicolliRobS said:
, does this awsome service manual contain rebuild info on the P/M? I would think it does, but I have never seen one. If you can rebuild a motor, a master cylinder is a piece of cake. BUT, you need to at least have the blow up diagram of the internals of the P/M. You dont want to get any parts mixed up and cause the P/M to malfunction.Never heard of prior. What kind of warranty do they offer if any?
It has a pretty good diagriam of the master cylinder. Plus it has the parts numbered with a step by step guide explaining what parts to remove when. It has no info for rebuilding the electric motor and pump.
The maufacturer was closed when I ordered the part. I am going to call Monday when they open. If its not lifetime I'm not buying. Rob
You should have it made then if you decide to rebuild. I would recommend that if you do rebuild, clean all components well with denatured alcohol bafore assembly.RobS said:
To my knowledge, there is no rebuild possible on the pump/motor.
Hank Terry sells NEW pump and motors. Search for his name on the brakes page and you can get in touch with him.
Yea, be cautious.RobS said:
Good luck!
Tom Walker
Tommy2Tone
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- Jul 18, 2004
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How did it go
ROBS, did you rebuild the PM? What did you find?
ROBS, did you rebuild the PM? What did you find?
Yes I did do a rebuild. Pep boy's could not get a powermaster. The only stores that could was autozone (they said it was avalible)$500, kirbin $500 and karps $1000. I ordered the rebuild kit $100. I still have the same trouble. I think its the power piston or the check valve on the pressure side. The service manual recommends the power piston to be replaced as an assemly so I did not disassemble it. If I could get the parts for the powermaster without breaking the bank, I would fix it. I am thinking of going manual brakes.
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