I own a '07 GT with now 95k miles on it, today after a few hours of casual driving the antifreeze began to spew out (noticed the antifreeze hitting the ground while the car was parked). As I attempted to twist the cap open more and more pressure began releasing, after about 10-15 minutes it finally cooled. The temperature gauge in the car at no point indicated the car was hot-any ideas what could have caused the pressure/heat to build causing the antifreeze to spew out (burst out from underneath the cap)?