bleed brakes no leaks air in there

hey have bled the brakes on the 87 MJ multiple times and no leaks, get the air out and then after use they get air in the system, NO BRAKE FLUID LEAKS. wtf is up TIA john

Whereabouts is the air bubble forming? Does it take a long time to come out (nearer the master cylinder), or is it quite quick to come out (nearer the caliper end)? Is the problem isolated to one particular caliper? What state are your joints and hoses in? Have you let the master cylinder run dry during bleeding at any point? Just a few thoughts...

Does your MJ have the load sensing proportioning valve in the rear? If so, is the air getting in the rear circuit? The proportioning valve in my '88 MJ died several months ago and made it impossible to bleed the system. In the process of trying, it sprung a leak. Fortunately I was working in the garage of a friend who is a retired Jeep master mechanic and service manager. He had a huge box full of old AMC and Jeep fittings, so we were able to find parts to cap off the extra line and plug the proportioning valve. I'm now running without it. Not too bad, but if I really stomp on the brakes on wet pavement I get more rear braking than I need.

There is a special procedure for bleeding the MJ brakes with that valve. Don't remember what it is, unfortunately. If nobody comes up with it, I can try to get my friend to refresh my memory but he was out of town for a few days. Should be back tomorrow of Wednesday.

just thoughts...
Did you bleed the Master Cyl. first, and seperately?
Did you lightly tap the calipers at intervals during the bleeding process?
Did you pattern your sequence, rr, lr, rf, lf?
ABS? If so, the HCU, hydrolic control unit must be bled after the master cyl, and beofre the lines, seperately.
Don't "pump up" the brakes to do the bleed, it compresses bubbles, and makes it even harder to manage the air out.

Like I said, just some thoughts. About eight years ago in a truck shop I had to learn about bleeding the Mast Cyl seperately the hard way. I thought it was to bleed it in place, right along with the rest of the system and do just fine. Sometimes you can slide by doing that, and sometimes not.

Heed the warnings of the ABS systems being under high pressure, and do all of you operations in the key-off or battery un-hooked position.

Best of luck with your repairs.

TheRasper.

He has an 87. Jeep didn't offer ABS on the XJ/MJ until 1989.

done all the above, believe that somehow air is entering during the up stroke of the brake pedal, It is only the fronts that are the problem and the master cylinder never ran dry so should be okay there. I am going to replace the front caliper hoses and see what happens, John