Pressure is from the heat.... temps must be very high. Does it got hot real quick?

Did the heat in the car stop first or did it stop after the overheating?

Could be a collapsing hose... or could be a water pump

check the hoses and make sure they are not really weak ....

any leaks?

Radiator cap check that too as it will suck air if it is not sealing correctly
_________________________
2006 LX with HPPBlue, Light Camel Interior,Magnaflow Exhaust,PI Zip Tube
Underdrives from ADTR.net
Pioneer AVIC X930BT Nav system, JL xD400/4amp, JL Speakers, Audiovox backup camera
Given to DG in Ohio

2013 Ford Expedition Limited EL, Pearl White

2000 HPP RESURECTION RIP 8/17/2012 died in Dayton OH