My 06 4x4 Mega Cab w/5.9 CD started running at around 200+ on the temp gauge this morning. Wouldn't worry me, but it ran about 190 consistently until today. And the temp seems to move up and down 10-20 degrees. I was thinking either thermostat or fan clutch. Anyone have any insight on this? Thanks.

 

Process of elimination. I always "burp" the system first, to eliminate air bubbles. If that don't fix it, then I'd remove the t-stat and put it in a pot of water with a kitchen thermometer in it...

 

Also check and see if both rad hoses are hot. It the rad itself hot all over. Might be a bad rad cap

 

Thanks guys,
This gives me a place to start .

 

If it does that on the highway, my guess is the 'stat, since the fan isn't used/needed above 30 mph or so. Mine would climb up past "normal", then fall back down to normal. That characteristic got worse and worse, so I swapped it out to a 180. No more weird issues with wandering temp gauges beyond what I expect.

 

Thanks Mike,
My symptoms are similar. I just took it around town and the temp seems pretty stable. I checked it out with an infra red temp reader and the thermostat tube to the radiator is 195, as it gets closer to the radiator it gets noticeably cooler. Bottom of the radiator on opposite side is down to near 110, so it seems the radiator is doing it's job. I'm going to order a 180 thermostat from Rock Auto and see what happens.
Thanks, Again

 

Before you order that stat, check out our thread on stats in our FAQs located HERE

 

Thanks for the advice. You don't happen to have the service manual for an 06 2500 w/Cummins TD ?

 

Srvc Man. No. But I got the Owners manual....

 

I installed a new thermostat, and water pump, and my temp dropped about 15 degrees on the gauge. Thanks for all the help!