I have been showing a high temp when driving around in the New Mexico heat. The car showed a 250-260 temp at one point cruising around with 100 degrees outside. What is the normal temperature for it to reach?

I went to check the radiator fluid level and surprise...no radiator cap. I twisted the overflow reservoir tank lid and it moved a little but couldn't twist that $%##@$ thing off. I could see dexcool in the clear part at the bottom though.

Both electric fans are running.

What'* next? I only have about 20K miles.

I would definately take it to the dealer and see whats up. Our gauges dont work accurately, most seem to show 200-210 although the engine comes with a 180 degree thermostat.Mine sits right at 200 all the time. But, the range you are showing is not norm. We have had a few unusually hot days here in PA in the upper 90'* and my GXP never went above 205. Under an extended NOX injection she hit 215 or so. Heat is a real enemy of the all aluminum LD8 and a host of problems involving warped heads, resulting water leaks and the damage that causes, and even popped headbolts. Never take an overheating issue lightly with a Northstar egine.. Mr. Goodwrench reps have told me that they seldom see a Northstar ever run the same after it has been driven in "limp home" mode.

yeah take it to a dealer right away. My gxp never went over 200 degress i recall. Did it change as you drove or stick around the same temp?

I wonder if the thermostat was stuck. The problem went away and hasn't happened since.