What could be causing it?? I thought that maybe the caliper is hanging up from repeated stopping BUT it does NOT appear to hang up . I pumped the brakes repeatedly in my driveway with the car OFF and the calipers did not Bind in a closed position. So I guess I can rule out a problem Caliper. BUT then why is there soooo much heat from the front centerline.
My next thought was the wheel bearings BUT upon visual inspection by removing the dust cap -- THE bearing grease is not burned or hardned- its still goooy like it should be.... sooo what is the cause of the heat?? Not sure if its the spindles BUT if the greases checks out OK then I guess the spindles are well lubed.

 

Still sounds like a pad dragging. Are both wheels the same? Have you changed anything? Did you check the rotors were centered in the calipers?

 

Make sure the slide pins are greased up good and free of any rust. Prob a caliper or pad hanging up.

Also, if you have rear drum brakes and they're out of adjustment, all or most of the braking is done by the fronts, causing the heat.

 

I'm gonna go out on a limb and guess that the one on the other side isn't getting NEAR as hot?

Probably the rubber hose.