Cooling strangeness - maybe a thermostat or fan clutch?

[01ssreda4]

First thing I would do is live time read the temp with a scan gauge or hptuners.

 

[willinnashville]

So, I got stuck in traffic yesterday and my Denali got just over 210 then back down again. I did not realize that was the efans activation point.

Thanks for the help. Turns out I just didn't know what was supposed to happen.