I removed the abs package off of my 91xj. I installed a brake booster, master cylinder, proportioning valve and new lines. Everything was fine for about ten minutes and then the front calipers locked on. I replaced the right caliper thinking it was more the right one and they both locked on again not fifteen minutes later. Any help would be appreciated. I completely rebuilt the rear drums using new drums, wheel cylinders, shoes, and hardware kits. Are my brake lines not returning flow to the master cylnder? How would i check this? Thanks

 

you may have contamination in the system, did you do a flush before installing all the new hardware?

 

yes and i noticed when changing the stuck caliper it was full of brake fluid. Would that mean there is something preventing it from its return path?