What engine temp do you run? And what is your t stat rated, 190? I am having some coolant issues. Truck runs around 205-210 on freeway. I have a 195 temp in. Seems to go up to about 215 before t stat opens when I get on freeway in the morning with outside temps at 28 degrees F. When I bought the truck it was running 200 and gauge never moved. I replaced t stat, rad cap and water pump (O Reilly's). New water pump is already leaking at weep hole after two weeks. Do OEM Cummins 190 T Stats really hold the temps much better than the local auto parts shops t stats? I read that NAPA t stats work the best from the local parts houses??

 

190 stat (not sure which brand, its what was their when i bought the truck). Runs 188 on the highway.

 

For water pump you better off goes for Cummins water pump.
For thermostat I had a Stant 190F that worked as the OEM. It keeps the temp at 188-190F.
The first time from a cold start it would open at around 195F then back down to 188-190F.

 

mine runs 178F on freeway even in hot AZ... I changed to 180F thermostat from Geno's... I recently cleaned out the font of the radiator as well, and I couldn't believe the crud I found in there.. I was running hotter when towing, and I think I found the culprit..

 

I changed to a 180 temp but it did not warm up quick enough for me when the temps are in the 20's. Switched to a NAPA 190 and NAPA water pump (Gates). All good now. Runs around 198 on the freeway.