After replacing nearly every cooling system part, I finally installed an Isspro water temp (actually tranny temp) gauge. Isspro reading at 75: 185* Factory gauge reading at 75: H, bout 2/3 of the way between the middle mark and the Hot mark. In other words, get a aftermarket gauge before rotting the radiator, replacing the thermostat twice, etc...I was not using my head...

 

Yes. It helps to know what things really are. The factory gauges are made without numbers because then they don't have the hassel of actually making them read correctly. As long as it reads somewhere between min and max is OK!

I feel the same way about my oil pressure. The factory gauge just says, "yes, you have some."

Edwin

 

Thankfully, "some" is usually all the Cummins needs.