It all started with a smoking hot rear axle bearing. Maiden voyage warped the rotor when the piston did not return and the pad stuck to the rotor. Put a new rotor on, completely cleaned the master cylinder, caliper, piston and put new oil in the system. Bled and tested the piston action in the shop, everything worked perfect dozens of times. Only made it five miles before the pad stuck to the rotor again. Now the pedal will push the pad against the rotor but the pad will not return. I did not replace any o-rings or banjo bolt washers. Could this be air seeping in the system or could my master cylinder need rebuilding? Thanks Guys!