I recently O/H my engine this summer. Replaced all parts and installed a new mopar radiator and coolant temp sensor but i am having trouble keeping engine temps to stay at the normal operating range line. Running the interstate no problem but around town and heat on its hard to keep temps up. I'm pretty sure the thermostat seat is installed correctly but haven't pulled it out to check it . Should I just install a new thermostat. The one I have is a cummins. Also is there different temperature thermostats