tbh999 - thats a tough one... given your description, it is hard to blame it on the caliper. Do you feel any pulling to that side? Or any pulsing in the brakes? Where I'm going with that is maybe there is a warp in your rotor and it is an intermittent rub - the caliper is pulling back but still rubbing cause the rotor is bad.

Perhaps try getting it up on jacks, do a couple brake applies, then get out and give the front wheel a spin by hand and see if you can tell where / when it rubs. This could hopefully lead you to a solution.

to rule some things out:
I highly doubt it is the Master cylinder - being a front/rear split you would see pressure in both front brakes. Its definitely not the booster. You only have rear ABS, so its not the ABS module. It has to be something at the wheel.

good luck!

 

I can't feel any "pulsing" on the brakes and the problem was present with both the original rotors and the replacements rotors (Brembo OEM type-not a "performance upgrade" type).

When the rotor got really heated-up it was like I was driving-up a hill all the time and had to give it a lot of gas just to keep the truck going. But that was before I replaced the calipers (I'm keeping my trips short now until I figure this out!)

I have spun the wheel and there does not appear to be any one spot that hangs. However, the right pads are dragging more than the left (takes more force to spin the wheel), however, when the pads are removed the hub spins freeling (so I didn't screw-up with the bearing preload). Everything has been changed on that side (at the wheel) and the problem is still there.

Do you know where I can get a schematic of the brake lines? There doesn't appear to be one in the shop manuals nor on AlldataDIY. Is there anything in the lines between the master cylinder and the calipers that could hold pressure on that one side...

 

not sure on the schematic

There shouldn't be. The only things that would be in a break line are Proportioning valves, or Load-sensing proportioning valves... but those are only for the rear brakes. The only other thought I'd have is a bad valve on the ABS module could be trapping some pressure... but you said you only have rear wheel ABS...

When you put the new calipers on... they came with all new seals and everything, right? Most calipers use the flexibility of the seals to pull the piston back and allow running clearance. That would be my next target for checking / replacing. Or take it back to the place you bought the caliper and tell them you want to exchange it? I'm thinking there could be an issue with the seal around the caliper piston.

 

I didn't pull out the pistons to check the O-rings, but both outside seals looked new. Also, I've had the same problem with TWO calipers, the original and the re-manufactured one I just put in. I know that it's possible to get a bad one, but the odds are a little slim and both times it was the RIGHT side (left side works fine, but I placed the left caliper too just because - My thoughs were that if one went bad [right], the other one [left] may not be far behind)...

Well, I knew it wasn't an easy question because I didn't ask it until after two weeks of trials and tribulations and I was completely stumped - I was hoping there was something odd about F-150 brake setup I was unaware of. I've had the system apart at least five times now, and the results are always the same.

 

Just a suggestion because I had this happen on my stang when I did a four wheel disc conversion, the one rear wheel kept overheating at highway speed and would drag a bit. Finally I figured out that the bracket was just slightly off square to the rotor, the caliper bracket somehow was slightly bent. Straightened it and now its good.