December 25, 2013I have a 2007 2500HD with a 5.9. In the past when idling in warm or hot weather even with the a/c on the engine temperature would always stay way below 200. Today with the outside air temperature at 70 degrees I was idling through heavy traffic I noticed my engine temperature at 200 degrees. Never saw that before. Once I got moving again the temperature went down below 200 again. Do you think you fan clutch is going out? I have 100,000 miles but flushed the cooling system and replaced the thermostat at 70,000.