Rear Brakes Overheating & Smoking After Brake Upgrade – Need Advice

Hey everyone,

I recently upgraded the brakes on my 2008 Mustang GT with a big brake kit up front (Brembo calipers, new pads, and rotors) and replaced only the rear brake pads. I also did a full brake fluid flush.

After the install, I took it for a short test drive in the rain and didn’t notice any issues. However, on a recent drive (only about 2 miles, max speed 40mph), I noticed a burnt clutch-like smell. When I stopped, the smell was much stronger, and I saw smoke coming from the rear brakes—looked like it was coming from behind the hub but hard to tell.

Worried about a fire, I ran into a gas station, grabbed some water bottles, and poured water on both rear brakes, which instantly steamed/boiled. I did the same to the front brakes for comparison, but they did not steam or boil, meaning the rears were way hotter.

I plan to get back under the car this weekend, but I’d like some advice on diagnosing the issue. I’ve read about pinched brake lines or locked calipers, but since both sides are overheating, I wonder if this points to something else.

Also, I’m considering buying new rear rotors since I poured water on the hot ones and am worried they may have warped.

Any thoughts on what could be causing this and how to diagnose it properly? Thanks in advance!