truck is an 02 F250 diesel.
all new brakes withing the past 2 months. 4 new rotors, 4 new calipers, new pads.
tuesday the passenger side rotor was 846 degrees measured by infrared .
checked caliper, the pistons retracted very easily, so i replaced the soft line thinking it may be starting to suffer internal failure..
last night the passenger rear was 450 degrees after 20 minutes driving.
this morning i pulled the wheel again, the inside of the rotor is tore up, but the pads are still like new. and the pistons in the caliper still are very easy to compress.
drove 15 miles, and the rotor is hot to the touch.
any ideas other than a bad brand new caliper?

 

I was asked to drop in on this post.

I would check if there is pressure in the caliper when it is dragging. Take along a wrench that fits the bleeder screw and crack it open and see if the fluid squirts out under some pressure. If it does, check if the hose was twisted when installed. If not, redo the test but check if the is pressure when the line nut is loosened at the hard line to flex hose connection. If so, it's most likely the ABS controller that has the issue.

The other possibility is one or both of the caliper Pistons is/are swelling when it's hot, keeping the pads tight to the rotor. I've seen this on several vehicles over the years. When cool they shrink and move freely.

 

the hose was definitely not kinked, i put it on the caliper, than bolted it to the rear, and on the hard line last.
if it was the ABS unit, would not both rear brakes lock up?
about the only system i have never messed with is ABS, and this truck is the only vehicle i own with a working ABS unit.
i have had issues with it back in june though, a headlight wire broke and made contact with the ABS unit, taking out the speedometer and disabling the ABS, which in turn also pretty much disabled the brakes. they would work on easy application but fail if you tried to panic stop.

the swelling caliper piston when hot was my thinking also. i guess i will try swapping the caliper in the am.

 

Sorry Tom, I was responding to this while having a conversation at the table and misread it as front brake. Yes, ABS on this vehicle would be both rear sides.

I would still do the bleeder screw check just to rule out any possibility. Over the past three to four years I've been involved in a few cases of the Pistons hanging when they are hot and its a pain in the tail to track down. I would also ask to check one other thing, how freely the pads move in the brackets. The aftermarket steel backs for the pads tend not to be as tight in tolerance as the OE specs are, but if they are wider then they should be, or there was excessive paint on the steel backs, they can get stuck in the brackets so they stay against the rotor. A tell is often only one pad I and its corresponding rotor surface is distressed, same as with pin issues. A few swipes with a file usually brings the steel back into compliance.

 

no problems with the misread.
pads are loose in the slides, that is the first thing i check when installing them. i learned that one a long time ago just like you did when i got a set that were a little too large and hung up. took me close to a week to figure that one out. customer was getting mad so i finally swapped out the pads and everything was fine. took the calipers to the pads and they were a few thousands too big causing them to stick in the brackets and ride the rotor.

the grand daughter gave me a bug, and i am trying to not fall off the couch as the room spins around me.
so i will take it for a ride to build up pressure in the wheel and try to see where it is holding once i can stand back up again.