Air in brakes again

[Marshall402]

I can't seem to keep my brakes air free so to speak. I have replaced both rear lines, master cylinder and bleeders and I'm still getting tons of air in my rears. It takes about 2 days before I lose them and have to bleed them again. I'm not leaking fluid anywhere, just sucking air from somewhere. I don't know much about brakes so if it matters it's always the rears, I'll bleed starting farthest away from the master so rear passenger is 1st and it takes forever to get air out and get some fluid flowing, next rear driver and hardly any air before fluid is running, next front right, no air, last driver front, no air. I have had problems with this it seems now forever and I can't figure it out. Do I need to replace the main line coming off the front before it branches to the rears or another master cylinder again or what? I'm lost and frustrated on this matter. Thanks for any help

Marshall

 

[Bobmbx]

What is happening to the fluid level in the reservoir?

Another question is how are you bleeding them? Are you leaving the bleeder open as you pump the brake pedal, or do you close it before allowing the pedal to come back up? If you are using bleed tubing and a catch bottle make sure you arrange it correctly.

In this photo the bleed tubing is arranged properly, with the high point of the tube above the bleed valve. This prevents air from getting sucked back into the cylinder.


This photo shows how not to do it.
Gravity will pull the brake fluid down and allow air to rise up and into the cylinder.

 

[smegun]

block of wood wedged between seat and brake loosen the master cylinder bolts push the seat forward leave it locked in place retighten the master cylinder lines ...repeat 3 times

I still get mush too I think it might be a bad vacume assist can when I got the truck they were totally tight and touchy makes me believe he did it with a vacuum assist
tool because its hard to get all the air out of the system and waiting for the parking brake to get the rear drums adjusted correctly is fun too shouldn't be that difficult
the above technique is from scotty killmer on youtube I got about 25 percent better action but it still isn't perfect but it isn't touchy anymore ither