Rear brake sticking before and after rebuild.

[TheFieryMan]

Well I had this issue start a couple weeks ago and parked it till I could rebuild the caliper, master cylinder and replace the rotor. In the shop the brake caliper works fine. It releases after it's released. On the road, if I use the rear brake it doesn't seem to release. I rebuilt the master cylinder tonight thinking for sure it would solve it. I had a nice glowing red rotor. I let it cool down and it releases after 5 min or so but I really don't understand what is going on.

[WingAdmin]

Almost always attributed to the return hole inside the master cylinder. Tiny pinhole that gets clogged, and prevents fluid return when the brake is released. Use a very fine wire to unclog it. Some people use a guitar "E" string, I've always just cut a single bristle off a wire brush and held it in needlenose pliers.

[Track T 2411]

If you've already checked the return hole, you might be dealing with a deteriorating brake line swelling or de-laminating...
One test that might help: when the caliper is 'stuck' crack open the bleeder. If it immediately releases, the problem is 'upstream.'

[FM-USA]

Had this issue also, different times front & back.
REAR_ Found one of the 2 slide pins were dry & stuck & wouldn't let the caliper release back.
Letting the line pressure of via bleed screw got me home.
Took almost an hour gently tapping back & forth with nut buster spray, patience won.
DO COVER the caliper cups from over spray.

FRONT-RIGHT_ Tiny air bubbles was the cause.

HOPE this helps.

[TheFieryMan]

Almost always attributed to the return hole inside the master cylinder. Tiny pinhole that gets clogged, and prevents fluid return when the brake is released. Use a very fine wire to unclog it. Some people use a guitar "E" string, I've always just cut a single bristle off a wire brush and held it in needlenose pliers.

Ok, I'm going to have a look at it again. I tried getting in there with the smallest wire I could get my hands on but the guitar string idea is good. It seems absurd to me that there would be such a small hole necessary in a system that uses a fluid that dries to a cement like material and clogs up everything.

[Rambozo]

It seems absurd to me that there would be such a small hole necessary in a system that uses a fluid that dries to a cement like material and clogs up everything.

Not a problem if folks would actually do the specified maintenance.

[TheFieryMan]

It seems absurd to me that there would be such a small hole necessary in a system that uses a fluid that dries to a cement like material and clogs up everything.

Not a problem if folks would actually do the specified maintenance.

Yeah this master cylinder looked like it hadn't been touched since it rolled off the line.