1992 Grand Prix brake problems
 

Yeah, for those of you that are aware of GM's poor rear brake design on these cars...I've been there, done that. Anyways, today, I replaced the rear calipers, pads, & rotors on this car, and while I was at it, flushed the brake system. The old fluid was nasty. I gravity bled/flushed the system, and when I had to bleed the rear calipers, I had to do it by the pedal. The fluid coming out of the rear calipers was nice and clean, and there was NO air in it. We didn't do this up front...figured good was good. Apparently, this is not the case. The car currently has virtually no brakes. I pumped the park brake multiple times, but that hasn't done much. May have a little...can't be sure yet. I drove it around, and the pedal came up only a little. I can get decent stopping power out of it, so it's not exactly unsafe to drive, just a little disconcerting knowing the brakes aren't RIGHT there, if you know what I mean. I'm guessing/hoping that air somehow managed to get in to the front lines...I did keep the master cylinder full while bleeding/flushing, but there was a five minute period with two bleeders open that I wasn't there...got called away. I'm going to bleed the fronts again when I get a chance, just to make sure, but barring that, anybody got any other ideas?

Thanks!

Heheh, seems like every time I see a W-body in a garage it's for a rear brake job!

I'd suggest bleeding the whole system, being sure to pump the pedal at all 4 corners (gravity bleeding doesn't work well in my experience). Bleed the left front, right front, left rear, and then right rear (going cloest->furthest from the master cyl). Pump the pedal about 10 times after you quit seeing bubbles just to be sure. I would be extremely surprised if that doesn't solve your problem!

Yeah, I'm thinking that's what I'm going to have to do. I don't want to do the rears...AGAIN, but I think I should as well. Pretty much the gravity part was for flush, and not bleeding, and I think it worked well for that, but I didn't finish it off correctly with a decent bleed procedure. Thanks.

I know for a fact that certain cars (the W body models from GM being among them) MUST be bled in a certain order. irseg's post is probably the correct one, but find out for sure from a GM dealer. you'll never get a good pedal if you dont do the order right. if, after going through all that, you still dont have a good pedal, then Id suspect either the proportioning valve or the master cylinder. Another good idea is the check the entire system (every single inch of lines included) for leaks/seepage. make sure the front pads arent low, as this can cause a slightly low pedal as well.