Ok heres the problem. A while back I posted about not having much rear brakes and everyone said to switch out to an adjustable proportioning well I finnally got around to it about 3 weeks ago and after installing it I had NO pedal I figured it was a bleeding issue and bled the hell out of them and still no pedal, So I went to a garage and had them vacuum bleed the entire system and still barely any pedal So I thought it was the master so I replaced the master with an LS1 master and I still have the same problem, NO pedal!!??? when I say no pedal I mean NOTHING for the first 4 inches then it feels like Im pressing against the wall and if I do this while im moving ill press against the "wall" a little harder and all of a sudden the front brakes LOCK up and the rears just laugh at me. theres no progressiveness to it its like an one or off switch. Im hoping someone has the answer cause I sure as hell have NO clue were to look now. before I switched out the proportioning valve I had brakes just it felt like the rears werent doing much.

 

Hmmm...the fronts get full pressure from the master so I don't see what the problem is, especially since you've pressure bled the system. Your symptoms still indicate air in the system but I can't be for sure.

Sorry I can't help any more than this.

Ed

 

How did you install the proportioning valve? You should have put it in the rear brake line and there are specific in and out ports.

Did you bench bleed the master?

 

The proportioning valve was put in the rear line and I double checked the in and out and its installed correctly. I used the rear port on the master for the front lines and the front port for the rear. I bench bled the master twice. The bleeder screws on the front calipers are at the top. and we vacuum bled, and then did a couple pump, pump, bleeds and the pedal never felt any different.

Now heres a question, IF the booster was what kind of symptoms would I see/feel?

 

I guess my only option is to try a booster. ill let you know if it works

 

Try bleeding the master cyl installed in the car . Have someone pump the pedal and hold it down then you crack the brake line at the master . Put a rag under it to catch the brake fluid . Do both lines a couple of times . When you install the master if you get air in the master it can airlock and be hard to bleed .

 

I agree with wanta427. Only crack one line at a time, and do it several times. Then pressure bleed the wheels one at a time using the brake pedal not vacuume bleeding. I installed C5 brakes on a 4 wheel disk 91 and it worked well with all the stock hydraulics. The front brakes will always lock before the rears on these cars if that is what your basing the opinion of the rears not working well on. But if your brake system was working fine before it should work fine after C5's installed. You may have to remove the aftermarket prop. valve in the rear. It only lowers pressure and you already dont think you get enough to the rear. I would think the newer style master cyl would be ok, but it may be better to switch back to where you started.
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I dont think the brake booster has any effect on whats going on. I wouldnt get one. You say the problem happened right after the prop valve was put in? The first thing I would do is take it out and make sure your rear calipers are working well and nothing is frozen.

 

See I would agree with you on most of that except the prop vavle has nothing to do with the pedal "feel". the first 4 inches of pedal travel are very very soft almost non existant. you can start to feel the car slow down but the faster/harder you push through that first 4 inches you dont get anymore stopping power. its only after those sloppy first 4 inches do you feel it get hard and its almost like the pedal is hitting something hard like a wall. From what I can tell if the booster blew its bladder you wouldnt get any kind of pedal till you have "pushed through" the buster bladder and then once your pedal piston comes into contact with the master would you start to get a hard pedal. So basicly Im thinking that if the booster blew what Im feeling after 4 inches is almost like manual brakes on a power brake car?

I checked the check valve on the booster and that is working fine, and ive backed the prop valve all the way in to provide 100% of the fluid from the master cylinder. the stock prop vavle has been removed as well.

Im picking up a used booster today for $20 Ive already spent $55 on bleeding and fluid so whats another $20 to rule out the booster?

 

WoooHooo Looks like the booster was the culprit, I still think I have some air in the lines but I got the majority of the pedal back and can actually panic stop! now its time to fine tune the rear brakes with the prop valve and ill be off to the races!