[Shiny]

Jimbro,

I agree. But then how do I diagnose using this method? Should I bleed between each test?

that's what I did.. I think I went through 2 quarts of fluid

....By plugging one half of the system (at the M/C) and leaving the other connected, I'm removing an entire system (front or rear) from the equation to try and deduce where the issue is. If I had some magical way of plugging the brake system that didn't introduce air, I should logically be able to plug the front, see the pedal is solid, hook it back up, see it's soft, then work my way down the brake system from the M/C until it's hard again to try and determine where the issue lies.

I wish I knew more, but somehow the m/c pistons must be independent for front and rear systems. If the front system was solid, and the back was all air, how would you ever feel the back soft effect if the two m/c pistons were tied together rigidly? The front would build pressure, the back would not, but you would only feel the solid front? Make any sense? This is why I am not sure plugging a single port at a time on the m/c is a good test. Maybe somebody with knowledge can clear this up?

Yes I heard about these! I actually replaced my wheel cylinders a few months ago with NAPA units. There was a definite improvement, but not enough, so perhaps it was one of a few issues.

I'll go with this one. I replaced my m/c, didn't fix. Then I found a leak at a fitting, fixed it, but still not right. I can believe you may also have more than one issue.

I still think you should block both ports on the m/c to eliminate it, then bleed, then sit overnight, bleed again, bleed some more...then put pressure on the system and look for leaks. If you don't see any, but the system is still soft, then you either aren't bleeding well or something is leaking. I am totally in agreement with chrisp that the leak could be fluid going out OR air getting sucked back in.

Here's my thought:

after bleeding, push and hold the pedal

if fluid is leaking fluid out, I think the pedal will slowly go to the floor

if it stays firm without moving, then pump it repeatedly

if this makes the pedal go to the floor, and you see no leaks, you are sucking air in somewhere. this is much more likely in the rear system than in the front as the calipers don't move much and the rear shoes can move a lot if no residual pressure is in the line

My combo valve is also from Inline, and I am pretty sure it does not have a check valve for the rear. I say this because:

1. I stuck a paper clip into the port and there was nothing there
2. I added a residual pressure valve to the rear and it made a big improvement.

Someday I will have a reunion with my car and replace the rear cylinders with the NAPAs.

I also never saw my switch trip when I had an imbalance. I am not convinced it works at all.

Good luck