I have 2007 cab chassis, 6.7l Has edge juice installed,, My temp started fluctuating from 187 to 210 while driving, changed thermostat, still doing the same, changed temp sending unit, still same problem,, any sugestions,

 

cant speak for your 07, but my 96 does that, runs up to temp, then the thermostat opens and it cools. has always done it on mine.

 

does it fluctuate like a oil pressure gauge, i have 168k on it and it just started doing it, my temp never exceded 199 unloaded, its 50 degrees out, im doing 70mph and my temp is 205 to 207

 

Is your fan kicking in? Are you getting any codes? Silly question, is your rad partially plugged up?

 

This was common on 12-valves, either it did or it didn't. My '95 AT 4wd Did - went up to almost 190 and then dropped to 140, over and over again.

96_12V dosen't do it, stays just over 140 all the time, regardless.

Now sure on a 6.7L unit...?

 

Both mine(last year) and my son's truck (last week), have had the same issue. It turned out to be the water pump dying(leaking). Temps started going over 200 unloaded, then one day open hood and antifreeze sprayed all over air intake box. If system can't build pressure it will not cool properly. Rockauto.com is the cheapest place I found them. Just look at the weeping hole for wetness.