Gambit69

Finally got my 89 firebird formula 350 out of the garage and took it for a small spin around town. Brakes have never really been the best but today after driving around for a bit the brake pedal would almost go to the floor, not al the way but the pedal wasn't moving anymore and the car was still slowly moving. It was slowing it down but kind of hard to get it to stop. If I put it in neutral to pull the power away I could get it to stop so they are slightly working. Haven't done anything to the brakes for about 6 years so they might be due for an upgrade. Now I have been reading around and I am guessing there is possibly air in the line somehow. The master cylinder resevoir is full and no leaks anywere. If I have the car off and pump the brakes a few times they get hard and if I keep pressure on the brakes and start the car, the pedal gets spongy and almost goes to the floor just like it was when I was driving around. Would this be a sign of a bad booster or is it still an issue of air possibly being in the lines? I am looking to redo the brakes soon and just want to know if I am going to have to replace the booster as well as the MC when I redo the brakes. Just looking for some help on what the problem might be.

Now for bleeding the brakes, I have a power bleeder from Motive products. The only problem with this is I can't get it pressurized as much as it wants because I can't get it to seal around the MC. Would it still work if I got it all hooked up, opened up a bleeder valve and started pumping up the take causing some pressure to build up to force the fluid out the bleeder valve? If anyone has any insight to this any help would be greatly appreciated. If anyone has any questions about the problem with the brakes or my way of bleeding please ask and I will give any info I can to help get the problem fixed. Thanks for the help.

regal301

i would get the car off the ground,visually check all the lines for leaks,then pull all 4 wheels.inspect the calipers, your car should have 4 wheel disc.if not check the wheel cylinders.then move on to bleeding if it dosent build pressure then its a bad master.

regal301

to bleed brakes i do it the old school way, the master cap off ,bleeders open until i get 2 drips per second out of the bleeder,then lock them up fill the master and cap it, have someone pump and hold, open the bleeder,close the bleeder. repeat untill no air then on to the next wheel.starting farthest from the master.

KITT1983

iTrader: (3)

Awesome KITT


I am having a simliar problem with my brakes, do you have any updates?

regal301

a bad booster will normaly give you a rock hard pedal (no assist)and you would hear a vacuum leak.

pedal to the floor is a blown line,wheel cylinder or bad master.

Gambit69

Okay, I just finished redoing the front brakes with all new hardware. Calipers, rotors, hose, bearings. Bled the brakes and still noticing that the pedal still travels quite a bit before it stops. Had the wife press on the pedal and noticed the little rod coming out of the rear of the proportioning valve. So this is telling me that there is something wrong with the rear brakes and that is why the rod comes out the rear of the valve? Any possibilities that could cause this? I know a leak in the line would cause this but would a bad caliper do this, or a stuck caliper? Just wondering what might be causing this? I will probably be taking the car to Car-X to get it worked on since I dont have the time to redo the rear brakes with the baby coming within a month. Have other things to worry about. Any suggestiongs from anyone is greatly appreciated. Thanks for the help.

JamesC

iTrader: (5)

Rod? There's a piston in the pressure differential switch that must be centered. If not, a leak has been detected in the system and a light will illuminate on the dash. Both ends of the combination valve are capped with what appears to be a rubber plug, so I'm unsure what the 'rod' is all about.

JamesC

Gambit69

Okay then it is the pressure differential switch not the combination valve. The piston that I think you are talking about is what is behind the rubber caps. If there is a failure in the rear system, this piston or rod will poke out the back of the switch and I believe shutting off pressure to rear part of the brake system. It would do the same to the front if the piston was coming out the front of the switch.

I can't seem to find a leak anywhere. I can get the front brakes to hold the car while I spin the rear tires which means the front brakes are working. when I look at the rear rotors the passenger side it is clean and no dirt or rust on it where the pad touches the rotor but on the drivers side It looks like it barley touches the rotor because there is rust all over the surface of the rotor where the pads would press against the rotor even after doing a small burnout testing the front brakes.

The brake light isn't turing on on the dash right now. I think I was working under the dash one day and seen it come on and I pressed on some wires and it shut off. Might see if I can find out if I wire came loose so that the light doesnt come on.

JamesC

iTrader: (5)

Here's how the switch works, taken from the following site:

http://auto.howstuffworks.com/auto-p...ter-brake2.htm

"Pressure Differential Switch
The pressure differential valve is the device that alerts you if you have a leak in one of your brake circuits. The valve contains a specially shaped piston in the middle of a cylinder. Each side of the piston is exposed to the pressure in one of the two brake circuits. As long as the pressure in both circuits is the same, the piston will stay centered in its cylinder. But if one side develops a leak, the pressure will drop in that circuit, forcing the piston off-center. This closes a switch, which turns on a light in the instrument panel of the car."

The brake system is a closed system, so if you're seeing a rod/piston actually come through the combination valve, I suggest that the valve is defective. BTW, according the manual, the only way the light can be turned off (short of disabling it) is to repair the failure and apply a pedal force to develop approximately 450 psi line pressure.

JamesC

Gambit69

https://www.thirdgen.org/forums/brak...pongy-why.html

Read through this thread. They talk about the same thing I am talking about with the rod coming out the proportioning valve. Do they not have any idea on what they are talking about? I do appreciate the help I am just trying to figure out what info is right.

JamesC

iTrader: (5)

The pressure differential switch's sole function is to make the driver aware of a failure in the system--it does nothing else. I've never read about or experienced the 'rod' business, so if there's something to it, I hope someone chimes in.

Rusty rotor. I assume your rear brakes have PBR's. If so, when was the last time, if ever, that the pins and housing were cleaned and lubed, allowing the calipers to float as they should? Check post #9 of the following link and take a peek at the Illustration part, numbers 26a, 26b and 30:

https://www.thirdgen.org/forums/brak...r-caliper.html

JamesC

Gambit69

Okay, now I have another problem and it might be just needing to lube up the rear calipers like you said. I tried to use my ebrake to see if the brakes rear brakes are working and no such luck. I pull up on the ebrake, but it in gear and it drives just fine and I dont hear anything rubbing at all. I had the wife pull the ebrake while i looked at the calipers and there is plenty of movement where the ebrake cable is on the caliper it just doesn't seem to move the brakes at all. I will try to get a video of what the brakes are doing when I pull the ebrake as well as what the front prop valve is doing when I hit the brakes. The fronts seem to be fine. They will hold the car still while doing a burnout so I am guessing it is all to the rear. James, thanks the the help and the info. For lubing up those parts you mentioned, what do you recommend to lube them up with and should I press the brakes while doing this or tap on them while lubing them up if they are stuck?

JamesC

iTrader: (5)

You'll have to do some disassembly to do the lubing (with a lube designed for brakes). The parking brake may need 'free travel' adjustment or adjustment in the tunnel:

https://www.thirdgen.org/forums/susp...ear-brake.html

https://www.thirdgen.org/forums/brak...-i-adjust.html

JamesC