quick solution: replace calipers, rotors,and pads.

 

FWIW and I'm not claiming to be an expert by any stretch of the imagination I would say it is very unlikely to have anything to do with another wheel. While it's common to replace rotors, calipers and brake pads in wheel pairs, what you're explaining doesn't seem to be possible. That would have to be the only brake working to cause that kind of friction, and you would know it / feel it the very second you tried to stop the car.

If you jack the rear end wheels off the ground, car in neutral, parking brake off and front wheels chocked, can you manually spin each of the wheels without excessive resistance or grinding? Is one significantly different than the other? While doing this check also make sure that the parking brake is working properly (on/off) as it should definately change your ability to spin the wheels. If brake is off and you can't freely spin the wheel then I would suspect the rotor or pads or both are incorrect...since you replaced the caliper and said that the slide pins / pads seem free. Then again, if all this seems ok but it is only under power that you experience this it could be some type of ABS malfunction and you might want to see if the ECU is reporting any codes that aren't yet registering on your dash. Hopefully the wheel sensor was reconnected or wasn't damaged. Also, from experience, ABSs don't like fluid being pushed back into the system when replacing pads. Fluid should be pushed out from the reservior or released from the caliper bleed points. I see a lot of people try to change pads by compressing the calipers and pushing the fluid back up into the reservior. This has caused many a system to be damaged.

Hope you sort this out soon.

 

LMG_35C has a good point,
One way to check if it is the ABS system dragging on that wheel is to remove the ABS control fuse ,You will get a CEL. Start the car and drive it like you normally would. If it is a wheel sensor, you might not get a slip light on the instrument display, but it could be applying the brake on that wheel. with the fuse out the ABS will be disabled.This would rule out any ABS failure issues.

 

Well, the cause has finally been determined. For all those on the edge of their seat: Bad NEW caliper.

Took the car to a different mechanic this time. The inside pad was still sticking to the rotor. (The first mechanic didn't catch it, apparently, which is exactly why I have a hard time trusting mechanics and do my own brakes.)They couldn't get the caliper to move along the pins as it should when bolted down properly. When they loosened the slide pins, the caliper moved along the axis freely. The piston moved freely, so that wasn't the problem. Either a misfitting bracket or some other issue.

Needless to say, I'll be exchanging the caliper for another one tomorrow.

 

Good to hear but how is it possible that the original caliper and the replacement were both bad? That would have be be phenominal odds to cause the same problem.

 

Well, I'm reserving final judgement until the new caliper gets here for the exact same reason. (Probably should play the lottery because I'm definitely beating the odds on this one.)

The old caliper had an extremely tight piston. Pretty sure that was the problem since the second mechanic checked out my entire brake system and found no issues. Even confirmed that the passenger side caliper was working as it should. The piston on the new caliper is working properly too.

When he bolted down the new caliper without the rotor, he said there was absolutely no give on the slide pins until they were loosened somewhat. I guess the only other cause would be if the part of the car that the caliper is mounted to is bent and thus preventing the slide pin to work as it should; although, the pins went in without issue upon installation. Will follow-up when the new, new caliper is installed and tested.