Upper Radiator Hose Pressure??

Hiya all,

Just got the wifes Dart all up and running again (Starter went out finally) and Noticed something peculiar. When the Car is Running, and even after it shuts off and sits for a while to Cold, the Upper Radiator hose is HARD. Like it's got a **** ton load of Pressure in it. Even after Sitting for 2 hours and cold again, I can pull the Cap off and it's under pressure. I replaced the Thermostat when I did all the tune up and new fuel pump and such (less than 100 miles on the new thermostat). It's the /6 in it and even after pulling off the cap, letting the pressure out, and then putting the cap back on, then starting it, not even 10 seconds after starting it the Upper radiator hose is Hard from pressure again. (Yes My Thermostat is installed Correctly). Anyone know what might be causing this???

Wife's Daily Driver so any help would be Greatly Appreciated, it's got me dumbfounded and the only thing I can think of is the Thermostat is bad. Looking for any other possibilities.

Dave