2012 Buick Regal - Brake Pedal Stays Down/Brakes Remain Applied

Brake will not return. Car sitting in hot sun. Put foot on brake to shift. Car will not more as brake will not disengage unless I lift the pedal with my foot.

My first thought would be the brake power booster. If you Google “2012 buick regal brake pedal sticking”, you’ll see a number of complaints like yours, many noting it was hot outside.

One site says it was the master cylinder.