I had noticed on my 5.9 that the temp was pretty rock solid. I kept the space between the radiator and the IC clean so never really had any problems - steady at just below 190.

On the 6.7 I can see the temp spike up to 200 with modest acceleration. It goes right back down, but I think there is a lot of fluctuation there. I assume its the because of the EGR cooler, but has anyone else noticed an immediate temp response? I never looked, but did cummins change the location of the sender?

Just strange behaviour, wanted to make sure it was not a faulty thermostat.

 

With the OEM idiot gauges... who can say?

 

MIne does the same and I also had a 5.9 and never noticed it move ever. This one goes up and then right back down?

 

Same here.

 

My old 12 valves used to go up and down constantly. My 07 and 06 and 02 5.9's all ride just below the 200 and stick there. If I am towing heavy, it will go maybe to 210 and thats it.