Powermaster

[Wht87T]

I've been having problems with my powermaster unit for quite some time now. When I step on the pedal iniitally nothing happens, until a few seconds later the motor kicks in and they work fine at that point. The accumulator has been replaced and it has the grey pressure switch. What do you guys think is the problem? TIA

John

 

[wlaukaitis]

I may be wrong but I think that is the way it should be. Waht does "they work fine at that point" mean?

now that gnntype.org is back up, there is a good PM diag chart.

 

[Wht87T]

Well when i step on the pedal there is a significant delay until the motor kicks in.

 

[Turbo6inKY]

Originally posted by Wht87T
Well when i step on the pedal there is a significant delay until the motor kicks in.

You have a leak somewhere. The pressure isn't staying in the accumulator.

 

[turbo nasty]

Pump motor builds PSI in the Accum and the PSI (Gray) SW turns the motor off and you should have enough for roughly 3 to 4 brake pedal apply's. Then the gray PSI sw senses low PSI and turns the pump back on and theabove process repeats it self.
The pump should not come on with 1 pedal apply.

Here is a basic test...With the key off pump the pedal until the pedal gets hard now turn the key on (but do not start the engine just the on position) the pump should come on and pull the PASS side reservoir down to 1/4(yes a 1/4) inch. And do it in about 8-10 seconds then shut off. If it is taking too long to shut off, not pulling the level down, etc. and you have a new accum and PSI sw then try replacing the motor and rebuilding the PM internals.

Not sure if you replaced the SW if not try that next. then the rebuild and pump. typing fast sorry for the run ons

Get the pump motor from Hank Terry it is the only way..it is brand new and he bought the tooling from GMand you save some bucks.

 

[Wht87T]

Well I didnt replace the switch it allready had a grey one. The accum. has the yellow stripe on it, so thats the correct one as well. So if my car dosent pass the test should I replace the accum first?

 

[gofstbuick]

The motor will only turn on if it senses low pressure from the switch. The accumulator maintains pressure and the check valve holds the pressure in the power assist system. The motor just pumps until the switch tells it to shut off. I'm a little confused here, does the brake system have power assist all the time? And the PM motor comes on when you push the pedal but otherwise works flawlessly. If so, there may not be anything wrong with the PM system.

 

[Wht87T]

The pedal feel is just not right when I'm drivin down the road if I go to step on the pedal its very soft and almost goes to the floor until the motor kicks in and the pedal gets harder. I hope thats a better explination.

 

[gofstbuick]

Before you go tearing into your PM system, make sure the brake switch is properly adjusted (by the brake pedal) and bleed your brake system. Also, check for hydraulic fluid leaks (wheel cylinders, calipers, bleed screws, lines, etc.,,).

 

[wlaukaitis]

Mine does the same crapola. It is an Autozone reman and it goes very close to the floor. Sometimes when I am at a light it will "loosen up" and the car will creep forward. It feels like the pedal drops a bit, very unnerving. My accumulator is the new style but it does not have the yellow on it (I think it may have come off when they cleaned/rebuilt it)

I replaced mine because it was:

A) Original Unit
B) did not have the new switch
C) old accumulator
D) according to gnntype, had an internal leak.

I am not sure if mine comes on with each brake application though.