Mastercylinder Tech Question

[FlyNLo17]

Got a 1990 Pontiac GTP McLaren. 3.1 L Turbo. The master cylinder has went out, it is an ABS unit. A reman at Advance Auto is $1100. The non-ABS is $140. I was thinking about installing the non-abs unit and just removing the abs all together. Has anyone done this?? Can it be done??? What all is involved? Any help is greatly appreciated!!

Thanks,
Dale

[55trucker]

It can be done....to remove the more complicated ABS unit and install the non ABS is straight forward. They both bolt onto the front of the brake booster in the same manner. What will probably NOT line up is the brake lines. I do believe that the ABS system does not use 4 independent lines as the non ABS system uses. There are 2 independent lines for the front and a single line for the rear that splits off into one for either side. You might want to confirm that. If so you would need to form new rear lines. As for the electronics side, your ECM will probably be *looking* for the input signals from the ABS *powermaster* (there is also a *controller* under the drivers seat) and seeing as those pulses won't be there it may get confused. But given the price difference between the two different masters I might well consider doing the same thing if I were in your place. note: $140 seems a little steep for a regular master....is that with or without the reservoir?)

[GutlessSupreme]

1st off, do NOT get a reman. for the powermaster 3 from anywhere but Prior Remanufacturing. All other units will fail again and cost more.

2nd, converting from PM3 ABS to vacuum brakes is NOT as straightforward as that. There is no external booster in the car for the brakes with PM3, and vacuum brakes will not bolt up. You have to swap the firewall plate. Also, as said you only have a single rear brake line that splits off at a proportioning valve in the rear. Besides the fact that the regular MS needs two lines for the rear, the front lines won't bolt up right either. It IS doable but it's a significant amount of work.

Also, the ABS computer does not communicate with the ECM at all.


Review this page:

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

by the way, the Turbo Grand Prix is reffered to unofficially as a "TGP." GTP is a trim level on '91-'96 Grand Prixs with the 3.4 DOHC or '97+ with the 3.8 S/C.

[55trucker]

Knew we could get someone to come forth & get the info needed, the GM service manual is not too explicit with its printed diagrams.....how deep (thick) is the firewall plate that the ABS's PM III fastens to to keep the PM III in the same general location as the regular master cyl. that sits on the front of the vacuum booster? Are there one or two brake pedal pushrods?....(one on the pedal & one at the PM III?

[Sonyman]

i second that "Gutless" It can be done, but you'll have to put in a little work. My GP STE came with one, yanked it out, put a regular one, no probs since.

[torq455]

i've removed all of my ABS wiring, sensors, and the computer that controls it all. i'm looking into a new master cylinder w/o ABS to adapt to the existing brake lines. damn things are expensive! just have to re-bend some lines. my ABS light came on, but then you take that dash light out.

[GutlessSupreme]

The firewall plate for the PM3 won't accept a booster. It basically has a flage on it that sticks out 1.5 inches or so and has two studs on either end that the MC bolts to. The pushrod goes through the middle. I've never had to remove my vacuum brakes in my Cutlass so I dunno how exactly that one looks, but I know it's nothing like my TSTE's. Not sure on pushrod differences.

Anything thing to consider... when they work, PM3 brakes are by far the best among 1st gen Ws. I hate the brakes in my Cutlass. Even when I had the larger '96+ rotors up front, it couldn't stop for shit compared to my TSTE.

[55trucker]

For the first few years after purchasing the car, I too wasn't satisfied with the performance of the brakes either. Taking the car back to the dealer when it was under warranty was a letdown as the Dealer Mechs. could not do anything *out-of-the-ordinary* because GM would not let them. Here's what I did...had the vacuum booster rebuilt (didn't need it), it's a dual diaphragm, using different application return spring to lower the pedal effort. Also, the master cylinder pushrod has almost 3/16" play between the end of the pushrod in the booster and the piston inside the master cylinder. I closed up the gap to 1/16" with a 1/8" shim. This alone shortened up the pedal travel almost 3/4". I also pulled off the master (disassembled it) and drilled out the 4 ports to the same dia. as the I.D. of the brake lines at their ends where they are fitted into the master (the ports are smaller in Dia.). as well, I installed a set of carbon fiber slider pins on the rear calipers to permanently prevent them from seizing. (the rear calipers that are on the car have been there for 12 years now and still show no problems). After doing these mods I can lock up all 4's quite easily which is a lot better than before when I couldn't even lock up the fronts.( which wasn't toooo reassuring) ...(didn't mean to do a hi-jack here)