Need advise on brake issue

[dirtplay18]

Having an issue with both rear calipers sticking on my mod, they do not lock tight, but have lots of drag. Car sat for a few years (in garage) before I bought it. I did bleed the brakes and allow the fluid to drip for a while to make sure I had fresh fluid. Ran the car only 3 races and only noticed issue after last race. Calipers seem to compress without much effort, so there doesn't seem to be a restriction issue. Brake bias gauges showing normal, my guess is the air bleed is clogged in the master cyl?? If so, is this something I can re-build the master and correct?? Just wanting some advise before I open up the sys, car had great brake pedal.

[JustAddDirt]

replace master cylinders and all the brake calipers.
check to see if the rear mounting brackets have been bent.
take off caliper and compress the piston. reinstall it without the pads, put in the pins and tighten. move the caliper back and forth on the pins to make sure they are moving freely.

[7uptruckracer]

You can get the kits to replace the seals in the calipers they could stick or have rust or something in there causing an issue if you have any kind of line other then steel you could have an issue with it sitting its a good idea to replace or refresh all your seals in the calipers and master cylinders like he said.

[dirtplay18]

Going to try to re-build the master first. Both screwed up at the same time, makes me think its a master issue. Slides are free and brackets straight. Guess I should have specified this is a dual master set-up.

[7uptruckracer]

I forgot how we use to check that I think if we could get it to stick we would bust the line loose at the T for both sides and if the calipers released and freed up both wheels then you could rule out the individual wheels

[Lt.Stryker]

If you had a stiff pedal it may not be a master cylinder issue. I've had a couple of master cylinders go bad and the result was a spongy pedal that had to be pumped before building pressure in the system. Are you running an inner mud plug on the left rear? You'd be surprised at how much mud gets caked in the inside of the wheel and that can seriously affect the feel of the rear brakes... BTW, you can make an inner mud plug from any 15" air breather lid with a simple reamer bit. It's a lot better than buying one for the $38 they're asking.

[dirtplay18]

No LR inner plug, can duplicate in the garage. Immediately after pumping the pedal the rear wheels are really hard to move, after a few minutes, they both seem to free up a very small amount, both the same. The calipers can be squeezed in easily, all steel line with -4 braided to the calipers. brake bias gauge does return to zero every time the pedal is released. I've popped the axles out of the drive plates to eliminate gear drag.

[7uptruckracer]

Do you run residual valves at the master cylinder, only relevant if you have low mounted master cylinders if not something is holding pressure on both rears check your pedal assembly but sounds like could be the master cylinder. They usually bypass not Hangup but the seals could have swelled. It's a good idea regardless if it's the fix or not you can get the cylinder rebuild kits for like 30ish bucks just specify bore size.

[7uptruckracer]

Best way is when it hangs cut the bleeder valves loose see if it frees up I'm not positive but braded lines still have a liner, could have a line that's collapsing when you lift you foot up and holding pressure

[Lizardracing]

Make sure the pedal is returning fully. If it doesn't the internal bleed port stays covered by the piston and it doesn't fully release.

[dirtplay18]

The pedal is returning fully, I also made sure the pedal rod was adjusted into the balance bar block correctly. Really appreciate all the ideas!!

[dirtplay18]

Got the problem fixed, took lines off both calipers, still stuck, removed piston from calipers, found rust build-up in caliper bores and on the pistons, polished everything up, replaced seals, working normal, no binding. That's what I get for getting in a hurry. thx for all the help!!