I am having a heating issue with my 2001 4WD Blazer. I have changed the 190 degree thermostat twice, had a radiator flush and it is still running @ 210. The second thermostat seemed to be doing alright until I drove in city traffic (city streets not stop and go rush hour) for about 20 miles round trip. Parked for about 10 minutes and got back in for a 2 mile jaunt. When I was on the 2 mile return the thermostat was back up to 210. I shut it down gave it 5 minutes and turned it back on. Temp rose all the way up to 230 and went back down to 210. Prior to that the vehicle was dead on 190 degrees. Radiator was replaced about 3 years ago. Any suggestions where to look next? Thank you for any help.

 

Is the temp fine when driving on the highway? If so, it could be a bad fan clutch.