Testing the accumulator


New Member
Anyone have, or know of, any information on how to test the accumulator ??????
Almost sure the accumulator is bad, but want to make sure before replacing it. :)
Does the motor run everytime you press the brake moderately? If so the charge pressure has leaked down and needs replacing.

If it pumps up and turns off and the brakes feel normal but the pump has to turn on right away again it is the accumulator. If the pump turns off and the brakes don't feel very good its probably the pressure switch turning it off too early which you could test by manually jumping the switch to raise the right pressure, just don't over do it.

I guess it needs to be replaced. This is what happened.
Peddle would almost go to the floor and pump would come on after about a minute. Figured brake and power sections were leaking. Got the kit and rebuilt it. Master side cups were worn and the power side had a bad O-ring. Brakes work fine now. Pump comes on when you turn the key on. Pumps for about 15 seconds. Only thing pump comes on everytime you press the peddle. I figure the accumulator has lost it's gas.
Thing cost and arm and two legs!!!! If it cost only an arm and one leg I could still drive, but without legs kind of hard. That's why I asked to see if anyone knows how to test to be sure accumulator is bad. I know it can be done with the gauge set up, but not enough of these systems around to justify the cost.
Anyone ever have the nerve to cut one of these open to see what's inside???? :D
Inside is a bag of nitrogen. The precharge is something like 300 psi when working right. Until the pump reaches 300 psi, the bag is rigid. The bag allows the accumulator to be much smaller than one without a precharged bag. Search under my name and you will find a thread on accumulators. I investigated aftermarket generic accumulators. They are available in sizes way smaller to huge things for large hydraulic machines. There are plenty of rechargeable ones out there that could be used if the GM ones become too expensive. For now I bought the Autozone PM unit complete since it was cheaper than buying just the accumulator. Whoever rebuilds them is buying the accumulator cheaply. We just need to find out who makes them.
I heard a while back that someone had the stock acc. ball recharged. I seem to remember that it cost about $15 to do this. It sounds like somebody is on the ball :D

The rechargeable ones have a port on the outside. Its possible there is something under that center bump but I wouldn't think so. If someone has done it I hope they chime in.
I've never been able to find out much more about who or how you can recharge that bag of nitogen.....sounds rather difficult. And from my notes, it seems that this same person also has a way to get about 12 or so uses of the brakes before the motor comes on for a recharge..... Sure wish I kept better notes :mad:

Changed accumulator

Repalced the accumulator with a supposed good one. Pump comes on after two pumps. Something else is happening now. After the pump stops, after a few seconds, it kind of pumps two or three single pumps. I'm wondering if the switch is going bad. Brakes work fine, better than ever since the rebuild.
I always thought you should get at least three pumps before the pump comes back on????
Go through the powermaster troubleshooting guide at www.gnttype.org. Turn the key on, wait until after the pump turns off, turn off the key and start pumping the pedal. You should get 8-12 pumps before the pedal goes hard if the accumulator is good. Sounds like either the accumulator or pressure switch is bad in your case.
Seems to be ok

I've been fallowing the Powermaster troubleshooting booklet. It's ok, but not enough real life tips.
Brakes seem to be working ok. Except for the pump "burp" everything is much better than before.
Only thing to look for now is a spare pressure switch. :D