PM III Troubles

[cheekie253]

I own a '91 Pontiac Grand Prix LE which I know has a PM III system. Lately it has been acting up and the ABS light is staying on solid and the brake light comes on when I press the brakes. The pump runs constantly when the car is in the "on" position and when it's started. It does shut off when the car is off. When I first start it it will take a second to come on and will pump about once every second. It will pause for a second or two when I press on the brakes but once I hold down the brake for a while it will start up again. (which is quite annoying because it dims the lights). The brakes are spongy and it almost feels like there's air in the lines, but I just had the brakes bled. It isn't loosing any brake fluid either. Please help if you can. I went to many pages about this system and think it might be the accumulator. If it is can you give me a good place to go other than a dealership.

 

Thank You Bunches,

Cheekie253

[Pontiac6KSTEAWD]

Posible air build up in the ABS module? I have heard of this, and I think my car has this. My ABS light comes on at random. Sometimes flashing, sometimes just staying on. If I pump my brake pedal 2 times while the car is running, let the pump do its thing, shut the car off, and restart it. The light turns off. This has been going on since I replaced my rear cals and pads and rotors and bled the system down with new fluid. Not sure what the hell is going on..

[cheekie253]

I've just noticed something else, the ABS is engaging a little while I'm driving, without pressing on the brakes. My brake light doesn't come on and it feels like their lightly tapping on the brake without me even touching it. I thought it was my tranny slipping because it only happens when I'm at a constant speed, but my tranny sounds fine. I'm really puzzled now and the car's going to be parked for a while.

[herb427sc]

It is probably the accumulator.

 

Look at http://www.priorreman.com 1-800-444-4821

 

You can get the phone number from that web site.

 

I just got one for $99 plus shipping.

[Crazy K]

http://www.tpsgarage.com/TGP/brakes/powermaster.htm

thats some good info, read it!

[slick]

My Z34 started doing this after I had replaced the pads and rotors all around and bled the brakes. It got annoying real quick, and I couldn't find an answer for it, so I simply pulled the fuse.

[peeeot]

You say you just had the brakes bled.... the PM III needs to be bled in a very specific manner. If whoever bled your brakes didn't know the right procedure, they may have made things worse rather than better.

 

http://www.tpsgarage.com/TGP/brakes/powermaster.htm gives the correct procedure for bleeding. If you suspect they were bled incorrectly, it wouldn't be too hard to bleed them again, according to that procedure, to make sure that isn't the problem.

 

Your accumulator could be at fault. Would it show physical signs of leakage, such as fluid on the outside/base of the accumulator? I would check for any such sign of fluid leakage. You may be losing brake fluid in very small quantities.

 

If you haven't done it yet, check your rear proportioning valve (next to the fuel filter, on the driver side in front of the fuel tank) and make sure it isn't leaking. Your system's behavior sounds a lot like mine, and my prop. valve is leaking.

 

When you've located the source of the problem, order the part from gmpartsdirect.com. They have the best prices I've seen. I've listed part numbers and prices here--> http://www.w-body.com/forum/index.php/topic,45255.15.html

 

Good luck and keep us posted!