Last winter I replaced my thermostat as I wasn't getting warm temps. The needle was just above the 160 mark and the heater air was luke warm. Replacing the thermostat fixed that. What I'm now finding is that I seem to not have any pressure build up in the system. My upper radiator hose does not firm up (no that's not a euphemism you sick bastards!) at all. I don't over heat, there's no visible loss of coolant, my oil looks perfect, no steam. I'm concerned but there seems to be no side effects but I know it's not right. Anyone have any thoughts on this?