I was pondering the thought of replacing this expensive master with a non-ABS unit. I would prefer not having ABS on this car for driveability and better driver feel/control. Has anyone done this? Thanks, Rob
Yeah, I actually have. A couple other guys have too.
The "right" way to do it is to remove the dash and replace the firewall. However, I went to the junkyard and cut a section of the firewall and used it as a template and cut the existing firewall. The only problem is the seal on the booster can be used as it is sandwiched between the firewall and brake pedal normally. So there isn't any way to seal the hole. I'm not even sure how it works from the factory, it just doesn't seem like it would seal well looking at my mock up on the floor. So we are probably going to use spray foam or something else to seal the hole.
I used a camaro master cylinder and kept the existing lines. I reflared them with standard fittings and used a 3 way block for the front two lines and an adapter for the back lines. I wanted front rear bias instead of the dual diagonal, but you could just replace the rear lines and use the factory GP setup w/o abs. You will have to deal with the red abs light too, as it will come on without the PMIII in there. I jumpered the wire in the harness to ground for the red light and removed the yellow abs light from the dash.
Works pretty well so far. I would do it this way again, but try and figure a way to seal the hole in the firewall. Oh, I almost forgot, you will have to cut the studs down a little on the firewall or the booster will hit it. I had a hard time until i figured that out. You can take a couple of threads off an it should be enough in case you want to go back to the ABS setup.
Chris
Chris,
I am going to go to the pull apart junkyard this weekend and get a vacuum booster brake system off of another grand prixand attempt the conversion. You have a lot of insight and experience on this. Is there a setup that you would recommend?
yeah, try and get the 89 or 90 w body setup. There are small differences in later years that I can't explain. I may have just had a bad booster, but I got one off a 92 or 93 cutlass and it didn't work at all. Went right to the floor with the engine running. I though I had made a major error in the MC from the camaro, but it ended up being the booster. I got one from an earlier year (90 to be exact) and it worked perfect. I don't know if it was a coincidence or not about the year.
Also, the 90 vacuum hose is part metal and part rubber. I didn't care for the way it fit originally so I think I finally settled on one from a 93 or 94 lumina. I can get a pic of it so you can see, but I fit very nicely and stayed away from the downpipe. I was in such a hurry for this project (because the booster was bad mostly and I had to scramble when I figured it was the problem), I didn't get good notes.
If I did it again, I would see how it went to sandwhich the donor firewall part and seal retainer against the TGP firewall. The thickness it adds shouldn't be a problem and it will allow the original seal to function the way it was designed. Its the only way I can see getting the fire wall to seal, which is a big deal if its not.
I had to enlarge the pushrod hole some to fit on the pedal, again in a rush so I don't have much detail. I may have even use the pushrod end from a different year, but as long as it will fit and have a reasonable amout of material left it will work. It doesn't need to beshortened or anything.
The firewall studs need to be shortened a couple of threads for the booster to lock on. I had a big problem with this because it didn't look like it was the problem till I noticed the booster had small dents in it. I didn't want to cut them really short incase I had to reverse the procedure.
The powermaster wiring will have to have the pressure switch wire grounded to turn off the red brake light. I just removed the bulb for the yellow abs light.
You can use the GP master cylinder with dual diagonal brakes, and replace some of the lines, its really not a big deal. I just didn't want dual diagonal brakes.
various other details i'm too tired to write. keep in touch about it.
Chris
FYI: If any one wants a rebuilt PM III, there is one on ebay for $300.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2415327689&category=33566
I called Prior Reman. today and got a price on a new accumulator. $99.95. I thought that was a reasonable price considering the price jump that GM stuck us with. So everytime that I push my brake pedal I hear the pump run, and my anti-lock light flashes everytime that I drive the car. What is the best way for me to find out if it's the accum. or not? I'm a little annoyed by that light flashing all of the time. I don't want to spend the money on that if I'm gonna need a complete rebuild sometime soon. Anyone who could help would be appreciated.