I have a 2007 Kia Sorento. 3 weeks ago the front right caliper or brake started sticking. So much so that there was an extreme amount of heat coming from the wheel area. So far we have replaced the brake line to that brake, the caliper, and the master cylinder. We also disconnected the ABS to see if it was an issue there. Strangely enough, after disconnecting the ABS it ran fine for about 20 miles. Then back to square 1. It is only doing this on the one brake. Any suggestions on what I should be looking at to fix this issue?
Warped disc or incorrectly installed calipers or pads (e.g. sliders not sliding). Do proper test of manually spinning the wheels jacked up. Engine off and on. Pads may touch initially, but wheels should continue to rotate a few rounds after you start them spinning. If not remove the wheels, check calipers can be pushed L/R on the sliders by hand. Compare with good FL wheel.
When master cylinder is installed, a small gap must be correctly adjusted between its rod and the brake booster, so MC can fully open to release all pressure.
If ABS was electronically disconnected, while unlikely, it could still theoretically prevent a brake from releasing normally, if say a valve is stuck almost closed but permits more flow down than up. Could be noticeable when manually pedal-bleeding, that it would be harder to push through fluid compared to other wheel. (You may recycle fluid while bleeding if it's all new/flushed.)
The brake booster may self-apply. Lifting and holding up the pedal with your toe should retract it. If you can drive a few km with cold brakes and holding up the pedal, perhaps you may determine if brakes are less hot / not dragging.
If hydraulic lines out of ABS have enough play, and same sized threaded fittings you may try to swap FL/FR line. If dragging switches to other wheel, the cause should be above the ABS-outlet. Depending on the ABS unit, air in the system may require scan-tool for bleeding the ABS unit, but opening the ABS outlets and then bleed should only push the air from outlets down out of calipers, and not back into ABS unit. So ABS-bleed should not be required. Just make sure to not let reservoir go empty.
I have had similar issues with a malfunctioning brake causing one wheel to get hot.
One time it was caused by the tabs on the brake pads not fitting in the caliper properly. A little bit of work with a metal file allowed them to work properly.
Another time it was caused by one of the caliper guide-pins becoming rusty and stuck. Cleaning and lubricating the pin with the proper type of high temperature grease fixed it temporarily until I could replace the pin.
If you have not checked already, I would check that the pads and caliper pins can slide freely.