Good point about the pressure on the core. I put my cutoff on the top hose just because it was easier to get to that way, but I believe I will swap that to the push side and see if that makes a difference. I have a jiggle valve in my thermostat, which replaced one just like it because I wanted to be certain I didn't have a faulty one. There has to be some logical explanation for why the gauge goes to 200 or sometimes higher before that thermostat opens, when the cutoff is closed. If it is open, the temp never goes above 180. Thank you for the responses, very much appreciated.
