My car is a 13 Civic Si. 2 weeks ago I noticed a burning smell from the rear driver side and soon after a rumbling sound from that area as I released the brake pedal. I took it to the mechanic and he says the caliper was sticking. He replaced the caliper, but the problem of the rotor getting hotter than the others persisted. I took it back, he replaced the caliper again and the rotor was still getting hot. This morning after my drive in to work I took a temp gun to measure the rotors. The other three were at 40-44C and the hot one was at 70C. Seeing as how I've been through 2 calipers, I'm guessing the caliper is not the issue. What else could it be, slide pins, brake hoses, master cylinder, proportioning valve?