1991 Buick Regal ABS POWERMASTER III

[lionelc305]

Hello all!

My name is Lionel. I am French and I live in France...

I own a 1991 Buick Regal Limited V6 3.1L with ABS POWERMASTER III system.

The car runs very well with more than 215000 kms and is in perfect condition, except the brakes. And I need help because this car is so rare in France no one can repair and fix the problem. There is no US GM dealer here.

Let me explain;

The red brake light is still on, the amber ABS light is always blinking.

The car brakes, but the pedal goes untill the basement if I need to make a hard stop.

The Powermaster III motor never stops.

I have changed the accumulator but nothing changed.

I would like to change the pressure switch, but this part is impossible to find.

I would like to find a complete used Powermaster III without the accumulator to take parts and try to rebuild my ABS powermaster, but i can't find one.

But I ask myself if it will be not easier to change the powermaster for a conventional brake booster.

The problem is I don't know how to do that, even if I can probably find the parts on eBay or on rockauto.

If someone has a solution to offer it will be great.

Sorry for my poor english, I hope all is clear.

My email address is lionelcgz@free.fr

Thank you all for the help your could give me. Otherwise, I will be forced to through the car to a junkyard for free.

Edited May 11, 2011 by lionelc305

[Addicted2bass]

When the PMIII went on my Grand Prix a few years ago it took me almost an entire summer to get it fixed. I could'nt find a pressure switch so I was unable to get it rebuilt. I ended up buying a new one through Napa for $1400, at that time that was one of only two left in the whole country. Being that you are in France chances of finding the parts to do a vacumn brake swap are pretty low. Does'nt sound like there is going to be a cheap of easy fix for you:(

[White93z34]

Good luck, in the US its a pain finding parts for these systems.

 

Do a search on here for SIA electronics, find a way to give a call, ask for Kevin. they deal in tested working pressure switches since no one makes them anymore, I purchased one from them last summer for my Grand Prix. I paid $50 US for the one I got.

 

From what you describe it sounds like your pressure switch is shot. This system does not always have to be absurdly expensive to maintain but it can be. does your master leak brake fluid?

 

 

Now on the flip side you can convert your car to a standard vacuum brake system. you'll need (and I am amusing your regal is a 3.1)

 

Vacuum nipple that goes into the back of the intake plenum to replace the plug in there now

brake booster hose

brake booster

non-abs master cyl

fire wall plate

 

seems easy enough except that the dashboard, heater box/heatercore/ac evap core, steering column, pedals, lots of wiring have to be removed to swap your firewall plate out. it is no small job. and its held to the firewall by a bunch of 10mm nuts from the engine side so you'll have to remove enough from the engine bay side to get decent access to those nuts. after that you'll have to re run the rear brake lines as PMIII only has a single brake line to the rear wheels and non PMIII needs 2.

[55trucker]

As stated, the general practice when these units fail is to replace the complete item. The accumulator can be easily removed but trying to go further into the unit can be troublesome without the proper instruments to do so. A replacement unit from Rockauto is approx $1000, in Euros that would be less expensive but you still have to consider shipping as well. Is the car worth it?

To do a transfer to a regular vacuum assisted master cylinder is no small feat. Aside from getting your hands on a complete master cylinder/booster you have to replace all of the rear brake lines. No ABS cars make use of four independent lines directly out of the master (two to the front & two to the rear) whereas with an ABS unit there are only three lines. The single rear line splits off at the rear at a *T* junction then on to the wheels. Also there is a retaining plate that the master assembly is bolted to in the firewall that has to be replaced with an alternative plate to house the non ABS master assembly. As well you'll have to isolate the ABS computer so it is non active. Remember, when bleeding ABS brakes at the wheels never reverse the pressures in the lines. Always open the caliper bleeders before you push the caliper pistons back into the housing. Reversing the pressure direction can cause seal failures & unseat the solenoid pistons in the ABS master causing major problems. Here's a link to properly bleed the ABS master if by chance that hasn't been done at this time. Have a look at this exploded view and you can see what makes this puppy tick. All the best.

 

 

http://www.turbograndprix.com/absbleed.html

 

 

Edited May 11, 2011 by 55trucker

[mfewtrail]

This thread from last year might be of some help for you: http://www.w-body.com/showthread.php/48347-PM-III-questions-%28bad-pressure-switch%29?highlight=pressure+switch

 

See post #11 about cleaning the pressure switch there. Some Lotus Esprit owners w/ the same Powermaster III setup have had success in getting bad/sticking pressure switches to work after cleaning them.

 

Also, check out this link that I also posted in that old thread. It covers pretty much everything related to the powermaster setup including removal of items, troubleshooting, etc. http://arrc.epnet.com/autoapp/8800/8800.htm

[lionelc305]

Thank you all for the links and threads.

So now I have to try to remove the pressure switch and clean it up.

If ever that solution won't work, I have no choise. I will change the PM3.

If someone know where I can find the proportioning valve, it will be great, because mine was leaking before I repaired it. This is maybe a trouble too. And this part is impossible to find.

Thanks for that.

[lionelc305]

Hello again.

Someone told me it's possible to replace the PM3 for a 86-87 Buick GNX brake system with slight modifications. Maybe a PM2?

Do you think it's true or possible?

If yes, how to do that?

Thanks

[Addicted to eaton]

I don't see them being the same as thats a G body IIRC

[GOT2B GM]

I've had luck using a good used proportioning valve and pressure switch.

 

Finding new parts for the PM3 beyond accumulators is almost impossible these days.

[mfewtrail]

Thank you all for the links and threads.

So now I have to try to remove the pressure switch and clean it up.

If ever that solution won't work, I have no choise. I will change the PM3.

If someone know where I can find the proportioning valve, it will be great, because mine was leaking before I repaired it. This is maybe a trouble too. And this part is impossible to find.

Thanks for that.

 

Allworldautomotive.com still has the proportioning valve listed on their website, but I'm unsure if they have them or can get them anymore. The AC Delco number for it is 18M875. GM part number 88927272. I would try calling them and see if they can tell if you they're still available before you try to order one on the site.

 

Also, try sending a private message or email to LukeZ34 (the owner of this website & TGPForums.com). I know he had a brand new proportioning valve for sale at one time, he could still have it.

[lionelc305]

Thank you very much for your help. Irealy appreciate.

My priority is the pressure switch. If I can fix the problem I would not have to buy a new proportioning valve. But if the proportioning valve I have repaired is also the problem, I will have to change it, except if this part is dicontinued too.

Thank you.

[55trucker]

Thank you very much for your help. Irealy appreciate.

My priority is the pressure switch. If I can fix the problem I would not have to buy a new proportioning valve. But if the proportioning valve I have repaired is also the problem, I will have to change it, except if this part is dicontinued too.

Thank you.

 

^My good man......what does the proportioning valve located at the back of the car have to do with the pressure switch which is mounted to the master cylinder? All the proportioning valve does is to regulate the pressure to each of the rear wheels. These rarely fail, what is it you had to do to "repair" it?

Edited May 13, 2011 by 55trucker

[lionelc305]

Because when I bought the car 2 years ago the proportioning valva was leaking. So I decided to repair it. But on this ABS instructions, they say don't repair it, change it. That is why I would likr to change it for a new one. But if you think there is no incidence, I won't.

[lionelc305]

Does anybody know if there is a junkyard where I could find a used PM3 for parts. I see nothing on eBay site and the USA is a so big country, I told to myself maybe a junkyard could have this king of car with this ABS system in the background of the yard...

If someone have a junkyard address, just let me know.

Thank you.

[55trucker]

Because when I bought the car 2 years ago the proportioning valva was leaking. So I decided to repair it. But on this ABS instructions, they say don't repair it, change it. That is why I would likr to change it for a new one. But if you think there is no incidence, I won't.

 

All the valve does is to limit the output pressure to the rear wheels to a predetermined pressure with respect to the input pressure. When you say it was leaking I take it you mean the valve was leaking past the seal under the checkball retaining bolt. That's a minor situation and the valve really doesn't have to be replaced for the sake of that. But, are you certain that you have All of the air bed from the system?

[lionelc305]

Yes the system is completly bled and several times because I have changed the rear calipers+pads, repaired the proportioning valve and changed the accumulator.

I have bought the kent-moore bleeder for that+the kent-moore pressure tester. Now I bought the kent moore pressure switch tool to remove and try to repair the pressure switch, because the PM3 motor never stops. I hope I'll found the problem and solve it, otherwise the car will never be used again. Too bad....

[lionelc305]

Hello all!

You know what, I found 3 PM3 for parts! Yes! And where did I find them? In France. Incredible no?!

I have tried many places in the USA and in Canada and noone has a used PM3. But here after searching on the French Internet websites, I found w-body for parts and not expensive 350 to 1500 euros for a complete car.... Buick Pontiac or olds...

So now I am able to repair my PM3 unit on my Regal. Great!

If ever someone need w-body parts, I can provide, but shipping is expensive.

[55trucker]

Tres Bon! At least now you don't necessarily have to consider letting the car go. I hope the parts you get are in usable condition & better than that which you already have.