51 CJ3A brake bleed question

[Todd51CJ3A]

Need some help from the brake gurus. My 51 has no brakes until the pedal is all the way to the floor. The previous owner replaced the master cylinder, all hoses and brake cylinders. This was in 2019. I did find the right rear brake cylinder was leaking so ordered a new one and replaced it. I also adjusted the shoes on all four wheels using a feeler gauge. After replacing the wheel cylinder I started bleeding the right rear. Got some air then it stopped so went to left rear. Got some air and the bubbles slowed but would give a big burp at the last bit of throw on the pedal before bottoming out. Went back to the right rear and it’s doing the same thing now. The master cylinder did not run empty and I’ve pushed a quart of fluid through so far and can’t get rid of the bubbles. It seems to be sucking in air from somewhere…thoughts?

[bmorgil]

Todd, when you push on the brake pedal can you "pump" it up? Will it hold solid ever or does it just go to the floor? If you are sure there are no leaks, no fluid is missing after you pump it, and it never achieves a firm pedal, I am thinking the master cylinder is bad and leaking internally. There has been a rash of bad Master Cylinders.

The pedal should at least pump up and hold if there are no leaks. Air in the system will cause a spongy pedal and the system will have a low pedal that pumps up. In any case the pedal needs to hold firm and at a decent level. Anything else indicates a leak either internally in the master or externally leaking out. The air could be cycling back and forth in the master. The piston seal often is the culprit. If you cant generate good pressure, it is impossible to get the air out.