power master brake light coming on

[PaulRV6]

I just started the car after 1 yr and the brake lite is coming on intermittently, the car is on jack stands. The fluid level is good, the pump runs and the level goes down within 20 secs but when I push the brake pedal the dash lite sometimes comes on. What could this be??
Paul

 

[dwall]

If you want to keep the PM and don't want to fork over the $600-750 for rebuilt unit - here is my experience.

I had the accumulator ball replaced on two low mile PM systems. Get a known good (guaranteed?) replacement ball or new from a reputable vendor. Kirban sold me two used at very fair price after I got burned on one private party sale here on the board, BOTH of Kirbans are now on the cars and functioning without RED lights. Not saying that is your problem or is a permanent fix. In my cases, I had the light coming on without a hard pedal and brakes otherwise OK in each case. One system was due for a flush the other had just been flushed.

Plenty of help threads are available here on the board - as well as diagnostics.
Bob

 

[Mike T]

My car sat for a while and did the same thing that you are describing. It turned out to be an intermittent connection at the pressure switch on the top side of the PM.

 

[TurboDave]

I would suspect the accumulator. Don't drive the car until this is resolved or more damage could occur.

Sent from my QMV7A tablet via Tapatalk.

 

[Ttype6]

I just started the car after 1 yr and the brake lite is coming on intermittently, the car is on jack stands. The fluid level is good, the pump runs and the level goes down within 20 secs but when I push the brake pedal the dash lite sometimes comes on. What could this be??
Paul

You need an accumulator.

 

[josh young]

What style accumulator do you have? I had to replace mine and went with a new one from Kirban's. Another reason for replacing it is undue wear on your motor from all the extra cycling.

 

[PaulRV6]

What style accumulator do you have? I had to replace mine and went with a new one from Kirban's. Another reason for replacing it is undue wear on your motor from all the extra cycling.

Is there a way to be sure its the accumulator?
How much are they these days?
Thanks

 

[josh young]

The accumulator is most likely not holding it's charge so to speak, and is leaking back into the reservoir. From what I've read you can have 4 main issues with the Powermaster: the motor, the switch, the accumulator, or a leak in the system somewhere other than the accumulator. If the pump was bad you wouldn't be hearing it run, and I believe likewise with the switch. So you are down to a bad accumulator or a leak elsewhere in the system. I don't really know of a way to check the accumulator other than replacing it with a known good one. Does the one you have have yellow writing on the outside of the ball? I bet that's what is on yours, if so it has quiet a few years on it. I spoke with Kirban's and he said the vast majority of the time it was between the accumulator and a leak elsewhere the accumulator was the culprit. If you do replace it you will want to change the fluid as well. Do you know the procedure for changing it out?

 

[josh young]

They are about 200 from Kirban's for the latest new style. I think he sells some good used ones too though.

 

[Ttype6]

Is there a way to be sure its the accumulator?
How much are they these days?
Thanks

You might also have another problem,but you definitely need a new accumulator. Turn the ignition on and depress the brake pedal to activate the pump.Leave the ignition on without touching the brakes. If the pump doesn't come on after a half hour,your only problem is the accumulator.

 

[gnxparts]

How do you fix the internal leak? I've read that you simply remove the valve and clean it , is that the case ..?

 

[PaulRV6]

I noticed that the lite comes on when I first apply the brake and then goes off when I push harder. Does this still sound like the accumulator? I replaced it once about 10 yes ago.
Paul

 

[GNRick]

You might also have another problem,but you definitely need a new accumulator. Turn the ignition on and depress the brake pedal to activate the pump.Leave the ignition on without touching the brakes. If the pump doesn't come on after a half hour,your only problem is the accumulator.

I've never heard of this method before. Normally the brake motor should come on with every 2nd or 3rd push of the pedal. If it comes on with every push then the accumulator is bad (or internal leak). My motor was coming on with every second push of the pedal before I smelled smoke and the motor fried.

 

[Ttype6]

I've never heard of this method before. Normally the brake motor should come on with every 2nd or 3rd push of the pedal. If it comes on with every push then the accumulator is bad (or internal leak). My motor was coming on with every second push of the pedal before I smelled smoke and the motor fried.

If there is an internal leak,the pump will start without depressing the pedal. the greater the leak,the less time will go by before the pump starts on it's own. If it doesn't start on it's own after thirty minutes with the key on,you don't have a leak.
There are two things that determine how many brake applications it takes to turn the pump on. The amount of charge in the accumulator and the on and off points in the pressure switch.

 

[Ttype6]

How do you fix the internal leak? I've read that you simply remove the valve and clean it , is that the case ..?

The most common cause is deteriorated O rings on the booster piston. This will be the first part that comes out during diss assembly. You can bet that this is the problem if you observe fluid leaking back into the reservoir through the rear port at the bottom of the reservoir.

 

[Ttype6]

I noticed that the lite comes on when I first apply the brake and then goes off when I push harder. Does this still sound like the accumulator? I replaced it once about 10 yes ago.
Paul

Yes.

 

[GNRick]

There are two things that determine how many brake applications it takes to turn the pump on. The amount of charge in the accumulator and the on and off points in the pressure switch.

Is the pressure switch adjustable?

 

[Ttype6]

Is the pressure switch adjustable?

No,but they aren't all exactly the same as far as turn on and turn off points are concerned. You can see this with a gauge.

 

[PaulRV6]

Ok, I am going for a new accumulator. Would you guys be concerned about installing a new unopened GM accumulator (P/N 18013994) as opposed to a new style one from Kirbans? I can get this one much cheaper but only if you think it is a good choice. Thanks for your help.

paul

 

[GNRick]

They go bad just from sitting.