Bonneville won't stop. Suggestions?

rea98d

My grandmother's 1992 Bonneville SSE's brakes aren't stopping the car like the should. I replaced one of the calipers, and it helped, but the brakes still aren't up to par. I can get a helper to pump up hte brakes, then open the bleeder valve, and brake fluid squirts out under pressure, but still no brakes. Pads look good. Any ideas?

alcan

It might have hard pads. They'll wear forever but don't have the friction to stop the car quickly without a high pedal effort. Try softer pads. And this thread should be moved to the existing Bonneville topic.

rea98d

I tried it in the existing Bonneville topic, and got nothing. Most of the guys over there are concentrating on the newer, supercharged Bonnevilles and how to make them go fast. Any idiot can make a car go fast, it takes a genius to make one stop (Or, something like that;-)

alcan

OK :-) Most hard pads have to get pretty hot before they start working effectively. Try the softer pads, I think you'll be happy with the results. They will have a somewhat shorter life but brake pedal effort should be reduced.

jgmilberg

Always replace calipers in sets, so go and get the one for the other side.

DO NOT PUMP UP the brakes to bleed them!! Small air bubbles form from the larger air bubbles in the system getting broken up with all the back and forth stuff. You will be bleeding them forever. Two methods I have used in the past are as follows.

1 With a helper in the car have them push the pedal like they are coming to a stop, and keep constant gentle pressure. Open the bleeder, when the fluid comes out and stops, close the bleeder and do it again. Do this on all 4 corners.

2 One by one open the bleeders and let gravity do the work, it may take a while but it does work if you have no one else around to help.

With either of these methods I usually bleed them until new clean fluid comes out. Brake fluid absorbs water and becomes contaminated, and should be changed every now and again anyway. So while you're doing it might as well, right?

One other often overlooked part on these cars is the brake booster filter. If you get a good high stiff pedal this could be the problem. It is usually in the shape of a dodge/chrysler fuel filter, small and black, placed in line on the vacuum line between the intake and the booster. Sometimes it is the actual fitting that the hose connects to going into the booster. Get a replacement for it and see if that helps. It is usually in the HELP! section in the parts store, made by a company called Motormite.

If you hear a loud hissing when the brakes are applied the power brake booster needs replacing. Slight hissing as the brakes are pushed is normal but once the pedal is down as far as it goes should get quiet.

Have you replaced the master cylinder? This would also cause the problem, if you get a lot of fade in the brakes 95% of the time the master is to blame.

The only other possibility I can think of would be a faulty proportioning valve, but those rarely go bad.

Hope some of the info is useful. Good Luck

rea98d

Thanks for the advice. I'm beginning to think improper bleeding is the cause of the problem, because the car seems to stop fine, but the pedal is too squishy. I got some advice from a shadtree mechanic who said that was the proper way to do it. I'll rebleed them (and change out all the fluid while I'm at it), and see if it helps. Now, is there any way to drain out all the old fluid, other than out the bleeder valve (which will take forever and a day).

jgmilberg

I have a tool for bleeding brakes. It is called a Mighty Vac. You connect the proper adapter to the bleeder screw and open it, then pump the handle. It puts a vacuum on the system to pull the fluid through. The tool runs about $25 US for the plastic one, and $50 US for the metal ones. Her is the link to the page to see what it looks like.

http://www.autotools.com/warlock/catagory/mityvac.htm