Front brake caliper not releasing

[riotten22]

Hey guys have a rebuilt brake caliper and it is not releasing. If I pop the bleeder screw i can push the caliper piston back in with ease. Does this sound like the master cylinder could be bad? Any other ideas ?

 

[AlphaDogChoppers]

Definitely the master cylinder. The piston in the master cylinder might be sticking. That would prevent the fluid from returning. A rebuild kit for a MC is only a few bucks.

 

[Reinhard]

This is very common. It's not always the master. Most of the the time I can repair a frozen caliper by simply taking it apart and clean it, making sure to smooth out the piston and bore and reassemble. If the piston and/or bore is really pitted and/or rusty it will need replaced. If the master is not leaking there's no need to rebuild- the seals are holding. Do the same thing- disassemble, clean, and reassemble.

 

[AlphaDogChoppers]

I'll differ with you on this, Reinhard.
His caliper is not frozen. If he opens the bleeder, the piston goes in just fine.

Also, just because a master cylinder is not leaking does not mean it does not need to be rebuilt. I have had to rebuild master cylinders that seemed to work, and did not leak, but there was plenty of corrosion inside which caused them to stick sometimes. The piston in the master cylinder has no mechanism to retract it except a little spring. If it sticks, the fluid will not return, and the brakes will not fully release.

 

[66replica]

My bet is on the MC as well for this one. Time for a rebuild.

 

[riotten22]

Master Cylinder was the answer Thanks guys put my rebuild kit in and the font caliper is releasing properly now. Man getting that old Snap Ring out is a pain in the ass !