Upper Radiator Hose Pressure??

The Lower Hose is NOT collapsing. She got home and the Hose was really really hard from the pressure built up in it, NOTHING coming out of the Overflow Hose into the overflow tank or even disconnecting the hose nothing came out. Gotta let it Cool off for about 2 hours before I even wanna attempt to pop that cap.

Safe to assume it would be the Cap then??

Also, has anyone bought this one or used this Pressure Tester from harbor Freight?? It doesn't specifically list any of the OLDER cars in the downloaded PDF Manual online.

http://www.harborfreight.com/radiator-pressure-tester-kit-69258.html