2002 Chevy Trailblazer LT
So I have an 02 TB 150k miles. Recently the temperature gauge has been fluctuating. When I start the car the temp usually goes all the way up to a tick below 210 then while diving it will fluctuate all the way down To 155. I can’t find any leaks from my 3 month old radiator and even when the temp dips all the way down to 155 I have the heat on and it still runs really hot and never changes . So I makes me think it’s not the thermostat. Would it be coolant sensor or water pump? Any tips would be appreciated.