I have a problem where my calipers will not release, the left front and rear right are worse, locking up solid. The other 2 don't lock but don't seem to release fully.

I have replaced the rear right caliper and rebuilt the others with new seals, new brake hoses, still the same.

I have even replaced the ABS pump

When the caliper is locked and I undo the bleed nipple, the caliper releases.

All that seems left is the master cylinder, seems like its not letting the brake fluid return when the brake is released.

Would this cause this problem, if so, I guess they cannot be serviced, only replaced?

 

You did not specify your car & model, but generally the brake master cylinder is rebuildable.


If you notice, the other side of the brake master cylinder is attached to your brake pedal. Go to Autozone or Advanced Auto and ask for the brake master cylinder rebuild/repair kit. If yours is not rebuildable, they will be able to tell you. The kit is approximately $20 give or take a few dollars.


You should be able to get it done in 1 day. You will need to purge/bleed your brake system afterward.

 

I forgot to answer your question. yes, it is likely that the master cylinder failed on you. It is working like a piston (more like an automatic syringe) inside your master cylinder. When you depress on the brake pedal, the piston comes down and force the hydraulic fluid (brake fluid) to the calipers to provide braking action. When you release the brake pedal, the piston is pushed back up and release the pressure from the calipers.

 

Yes, it was the master cylinder, of course it all makes sense now with the symptoms i had