Had my son-in-law replace my caliper, rotor and brake pad, and the van ran fine for quite a while. The front left driver side all of a sudden froze up, became hot and started smoking. My son-in-law replaced the caliper and brake pad one more time and all was well. Once again, it began smelling and smoking again so my son-in-law replaced the caliper and brake pad once more. It ran fine for a while and all of a sudden once again, it began smoking and smelling. My son-in-law says that it may be in the master cylinder, what do you think?
You should definitely check the brake line that runs into the caliper. Another thing that can effect your brakes like this is the climate in your area. If its very hot and your brake fluid is overfilled, brake fluid expands in the heat. When your brake fluid expands and its overfilled, it would have no where to go and could force your caliper out, and it will not retract until the fluid cools. I don't know if that is your problem, but it could be a factor.