Soft brake pedal is going to make me loose my mind.

[axelbaker]

So I am redoing my brake system and am slowly loosing my mind. The car had sat for 10 years before I bought it so I figured first thing is redo the brakes.

So far I have replaced:
the rubber hoses (ancient and cracking),
the entire set of hardlines to the rear (rusted out, the fronts are fine)
rotors
pads
master cylinder (leaking)
the bias adjuster (actually probably good, but it seemed seized at the time)

I've blown brake clean through all the lines.

All the calipers have been rebuilt, I did not replace the pistons.

I have bled the system every way I know how. The old fashioned way with 2 guys, gravity, and vacuum. I have bled every junction in the lines, master cylinder connections, the bias adjuster connection, at the "T" until no bubbles came out. I have bled it with the wheels on the ground as well as with the bias adjuster rod disconnected and tied in the up position.

So after all this, I still can't get a solid pedal. What am I missing?! Could I have go a bad MC when I replaced it? I got it from AR, so I assume it to be a good unit.

I have probably run 2 gallons of brake fluid through it already, no exaggeration. I've literally had the engine out and rebuilt since I started working on the brakes.

Thoughts? Tricks? Set the car on fire?

[davidbruce]

A few things come to mind, and you may have already eliminated them. When you say you have a soft pedal. Will it actually go all the way to the floor or does it just feel like it travels too far? If it goes all the way to the floor try stomping hard on the pedal. Does that help? May need to be done with engine running for vacuum assist. I have seen m/c's with bad seals but if you stomp on them the cups will flare and do their job. I know it's a new master but everyone gets a bad part from time to time. Often when trouble shooting we ignore the new parts because , well they're new. Double check that there are no leaks anywhere in the system. Did brake clean get into a caliper and compromise the seals? Did you bleed starting from the furthest wheel from the m/c (P/R, D/R, P/F, D/F)? Assuming that when you bled you were getting a steady stream without bubbles from all wheels and your procedures were good I would think you are on the right track. And that the master is bypassing internally. Just my .02c

[nelsonj]

From my experience, "soft" or "spongy" breaks have 2 possible causes:
1) Air in the system. This is the 99% of the time answer, but it sounds like you've bleed the breaks (a lot), and if you are getting pure flow, without bubbles, that is not the problem.

2) A leak in the system (usually under pressure). I had this problem and it didn't matter how many times I bled the breaks, they got soft and I got air in the system. It turned out I had to rebuild (change all the rubber) on a piston in the rear break. I couldn't figure out the problem until one day I came out and there was a puddle of break fluid under my rear tire. I traced the leak to the piston. Fixed it (kind of a pain but a very cheep repair), and haven't had a problem in years.

I'd suggest moving the car to a very clean place, perhaps lining the floor of the garage with newspaper, and then keep pumping the breaks, and push really hard, without letting up, as the breaks are soft and the pedal slowly moves down. Wait until then next morning and then look at the ground/newspaper to see if there is any evidence of dripped break fluid. If 'yes', you'll at least have an idea of the location of the leak - either under a specific tire, or somewhere along the break lines or the master cylinder. Then you can (hopefully) trace the exact source of the leak, and fix it.

Good luck, and let us know what happens.

(P.S. setting the car on fire is a bad idea in most cases).

Peace.