I have the engine in the Ford now . Unless I drive it hard keeping exh temp above 600 degrees it will not get over 160.If I get it up to 180 it seems to stay unless I do not have a load on it like going down hill or idling. I would like it to be at 180 at least .Do they offer a stat that is a higher temp. I am running the Ford radiator it is 60sq inches bigger than the Dodge one. Out side temps were above 70.

 

I'm not at all surprised. The Cummins is better at rejecting heat. Need to hook a trailer. Mine runs cooler than my 6.9L ever did when I used to have a F-250.

There is a 190* t-stat, in place of a 180 that you might have. Get a genuine Cummins t-stat. Not one from NAPA or Autozone. Also, don't forget the 2 rubber seals for the t-stat housing.



There is a chance that the rubber "donut" (separate from the inner seal "donut") on the t-stat slipped and is keeping the t-stat open more than it should be.