Unless the thermostat isn't opening all the way. Replacing it is a cheap way to eliminate a possibility. It may be possible to take it out completely just to see if it makes a difference

 

Have you checked the rad cap? Perhaps it's not on all the way or faulty. Replacing it is the easiest thing you can do and inexpensive.

 

I had my stat replaced , mine would open and close , they replaced the water sensor also , 162,000 on 09

 

Need to start with the basics;

Pressure test the coolant system, if it leaks down and there is no apparent coolant on the floor, then do a compression test while the coolant pressure guage is on the rad. If there is a leakdown of a cylinder and an increase in the pressure in the coolant system then it's a bad head gasket.

Although it's rare in such a new vehicle, it's not impossible. This would explain why your coolant is superheating.

My guess; bad head gasket.

 

Silly me, I thought tricks were for kids, lol. Howya doing oldjeep I missed that where he said it went up to 238...yeah something is wrong somewhere, tsat won't help that. Btw, if it is over heating that high it will pull timing as well. Netman said it right...pressure and leakdown test. And I did hear of one member on another forum that had a defective (not blown...weird) head gasket so anthing is possible.

 

238 is high but not out of possible range depending on the length of the grade. You say this is something new to the truck though, so that leads me to believe that maybe there is something wrong but occasional 238 is probably OK. The new hemi runs hot and it's by design. The hotter it is, the leaner they can run it and the lower the emissions. I'm often surprised by the oil temps I see when towing up long grades, yes, over 230 for the engine oil, so the coolant can't be too far behind. If it's not boiling over and going into limp mode, then it's within operating range.

 

Not the same engine but, the same symptons came up in my Dakota. Head gasket!!

 

What's the scoop on this thing, it's been almost a week...you solve the problem yet?

 

Replaced the tstat and radiator cap.

No coolant in the oil and no oil in the coolant.

Going to go another round with dodge...

 

The service manager from dodge will be taking the truck / trailer on a test drive on the Saturday after next. They said they will connect it to a computer for the trip. Well see...