bizzare brake issue

ACTUALLY, I seem to be having the same issue. HOWEVER, it's not nearly as bad, and I *think* the axle bearings are actually the problem!
The passenger side axle can move in and out slightly. Which must be causing some rubbing, although I didn't see anything to cause alarm when I disassembled the brakes last time!
Uhg. I am still way ahead of the game with what she is worth, and what I have into her. And she is such huge fun. But man oh man correcting all the slop and "full depreciation" on parts from years of neglect and abuse by PO's!!

 

I was having an issue with my 84 CJ7 brakes sticking. Not a lot, just enough to notice more resistance. I thought is was the drums at first sticking. Nope, everything was great and working as should. So I looked at the front calipers. There was some issues as there was gunk built up on the caliper pins. Cleaned the pins, bushings, and the calipers, and it worked for a short time. But after driving across town they would start to drag again. Rotors and drums were not hot, but slightly warm as you would expect them to be after hard braking (except there was no hard braking). Also, pedal would not return all the way back up, short .25 of an inch or so.

So, vehicle cold, brakes act fine. After driving 15-20 min, they start dragging. Re-analyzing the situation I started thinking wtf!? Why are they dragging?? When things get warmer, they expand. What is expanding??? Brake fluid!! Sure enough, pulled over and removed top and the fluid was up to the very top. Removed fluid from the M/C and, bingo! Problem solved.

I had put on a brake booster and new M/C in December when it was 35-34 degrees outside. Filled with fluid to "proper levels" at the time. Now it is around 75-85 degrees. With the extra ambient air temperature, friction from the brakes, and heat from the engine bay, that was all it took. As the fluid expanded, it could not escape the system. So, as fluids do not compress, they started to apply pressure on the piston and was causing the brakes to drag. Removing brake fluid allowed room for the fluid to expand, and no more brake issues for me.

Thought I would share incase someone else might wonder down that street.

 

Preamble to my issue; Drove the jeep all last year in Fresno 100+ heat with non-booster brakes no problem. In December I bought a booster M/C combo and installed and has worked fine up until 2 weeks ago.

So, brakes are hanging up again. Same issue, front brakes drag after I have been driving a while. Also, and I think this might be where the issue is at, the brake pedal doesn't return all the way back. It is only about 1/4" or so, but I adjusted my pedal up so there wasn't any play. So any play is sign there is an issue. Also, the reservoir for the front brakes is a little cloudy.

This leads me to think it is a problem with my M/C. Any clues to why this might be happening? Both disk drag, so I doubt it is the calipers.

My first thought is that there is a machining issue with the body or plunger of the M/C, that there may not be enough tolerance to accommodate the expansion and is catching not allowing the M/C to return and is keeping pressure on the caliper pistons.

Anyone have any other ideas to a possible cause? I am most likely going to get a rebuild kit for my old M/C and see if that helps.

 

Thanks for the reply.

I did have some slack (still is a little), but removed most of it to see what the heck was going on. I can physically pull the remainder of the slack up, but does not relieve pressure from the pads and the slack remains. I do believe that heat is the catalyst to the real problem. What it is affecting is I am not sure. I did have about a 1/2" play in the pedal before it engage the M/C. When I started having issues, the slack was a little bit more than I normal had it. Spring return is fine on pedal, but there may be an issue within the MC.

The proportioning block should not effect the system in this way, barring something really weird. I have new front brake lines, stainless steel lines.
To me, it is either the MC or the calipers (doubting that both brake lines are causing the same issue on both sides if they were bad). But the fluid is a little cloudy now, so something is a foul. I am going to look to see if the hard lines are compromised in any way (rust, bends).

I still am leaning towards something funky with the MC, but will adjust pedal back with some proper play, along with a inspection of hard lines (again).

 

I think I found my issue. Had to do a little research on M/C operation and found out something I didn't know.

When I installed my power booster M/C combo, I had to reverse the lines to match the brake line size. My disk brake line is attached to the smaller chamber, which is intended for drum brakes. Drum brakes on M/C have a residual valve to leave about 10 lbs of pressure in the system so you don't have to pump the pedal to get effective braking. By swapping the lines, pressure is constantly put on the brakes, causing drag. Which generates friction, heating up components, which causes expansion, which generates more drag.

So I am going to swap out the M/C for a correct one. Does anyone know if the line size is different between the disk/drum lines on power vs manual M/C?

Hopefully that is all that is wrong.

 

Not positive but I think they will still need an adaptor to make them right size