We have a very random issue with the rear brakes on our 2001 Supercrew 4x4. Every now and then one of the rear brakes sticks on, not by a lot but just enough to feel the extra drag and create some smoke. It's not the same side every time. The truck can go for over 500 miles of all types of driving, urban, highway etc with no problem.
We're not using the park brake at the moment just to cut that from the equasion.
Once the hot brake cools the problem doesn't occur again.
We've had the discs off, all the mechanical side of things are working fine, nice and free etc.
I'm thinking we may have a flexi hose issue? Maybe breaking up internally and not allowing the fluid to return after a brake application.

Any other ideas?

Cheers in advance