First I'll give an overview of what the problem is and what I've done to correct it so far:

First, I reassembled the top end of the motor after getting the heads ported. I got the engine up and running properly and went for a test drive. I quickly noticed the brake warning light was on and the brake pedal was very mushy and required me to push it fully to the floor to stop at all.

I checked the fluid level in the master cylinder and it was a bit low. I figured I had probably sloshed it around and got some air into the lines. I filled it up and bled the entire system (2 man method) except for one rear-inner bleed screw that was frozen and rounded off. I really didn't see any air bubbles go through so I gave it another try but it still didn't work.

I then replaced the master cylinder thinking it was bad and rebled the entire system except for that frozen rear-inner rounded-off bleed screw. Again, no luck.

I pulled the brake lines off the master cylinder and rebled it on the car. The front side seemed to spurt out pretty decent afterwards but rear didn't have the same volume/pressure of fluid coming out- is this normal?

Since I had the master cylinder off I needed to rebleed the system. I also thought that frozen bleed screw was a problem. I filed two sides of it flat and after alot of liquid wrench and many heat/cooling cycles with a torch I got it loose. I then went and rebled the entire system from the furthest caliper to the closest (pass rear - inner then outer, driver rear - inner then outer, pass front, driver front). I went through a quart of brake fluid and got all air out of the rear lines and the front passenger side. However, when I bled the front driver side, it seemed no matter how many bleed cycles I went through, I would hear the sound of the caliper groaning and then get a few bubbles every other time or so. With the car off, the pedal was still fairly mushy. Just to see, I gave this a try but the brakes were still no better than to begin with. I looked for leaks all over the lines and calipers but couldn't find any problems at all.

Any ideas what could cause this? Can a faulty proportioning valve exhibit symptoms like this? What about a failed/broken linkage in the brake booster causing low master cylinder pressure? Or could the calipers somehow be allowing air in but not leaking fluid out?

I'm really not sure what else to try so if anyone could point out anything I'm overlooking or other things to try I would greatly appreciate it!

Thanks

 

first off, how old are these calipers? to your knowledge, are they SS sleeved? you've been around awhile so i'm sure you know where i'm going with these questions. did the car stop o.k. prior to the engine work? did the engine come out? only reason i as is possible damage to one of the lines have you checked rotors for run out?
honestly, i'm kind of stumped if you have a soggy pedal just sitting still. i would think that a swollen line could have caused this type of mushy pedal. my best guess at this point would be to put the car up on jackstands and have a buddy pump the brakes while you check all the flexable lines.
mushy pedal just sitting there, weird :confused: