I have never had an issue with overheating prior to changing a leaking water pump. It overheats after driving around ten miles. I can hear the overflow bubbling/gurgling and the hoses have a lot of pressure raising the fluid level to the cap. It cools down within 15 seconds if the heat is set to high then the pressure goes away and the fluid level goes back to normal while the car is still running. I really am stumped on this and don't want to continue to drive with mandatory heat on. Any and all help is greatly appreciated.