If you have no remote ports, like on the rear or for a loader, then you will have to find where the test port is, and also the specs for your machine (PSI rating). It is usually on the pump itself or on the tranny, you could follow the hydraulic lines back and maybe find it. You should also try jdparts.com to have a look at your system.
I am guessing the "dime valve" (never heard that term before) is the pressure relief valve (PRV), it's also usually on the tranny somewhere, and it set the max system pressure. It's spring operated so I don't think temperature would affect it though.
At this point I am suspecting the pump.