C15 issues. Running hot, possible oil in coolant.

I suppose that's possible, I've only had this truck a few months, and it was considerably colder when I got it. My previous truck, with a Cummins, seemed to run colder, and not heat up so easily. It could be this simply has a hotter running truck, my previous being a 475 Cummins, this a 600 cat. I'll be keeping an eye on it, none the less.

 

I just wanted to update with the solution and more information;

I eventually decided that this truck was going to just run warm, I did get the coolant checked and an oil sample, everything came back normal.

Then weird things started happening. A few months ago I had intermittent issue with the motor feeling like it was missing, but only happened briefly after getting a truck wash, a mechanic suspected the harness connection going under the valve covers, so I simply avoided getting an engine wash unless I could sit and let the connection dry out.

Then one day about two weeks ago the motor derated. I limped it back home and took it to a shop, finally after a week they called and said they found a few issues in the wire harness, they fixed them and the truck was good to go!

It wasn't. A day later it derated again. This time I took it to a Cat shop (which I learned I should have just done right off the bat) and in 4 hours they diagnosed the external wire harness was shorting out to the clip holding it and the first shop never saw it.

The result; shorting wires for injectors, intake solenoids, which resulted in poor fuel economy and eventually triggered the derate. It also messed up a fuel temp sensor, and something with the diverter valve which I was told was causing the above normal temps.

Been running over the weekend with the new harness as truck is running perfect, back to normal temp and better fuel economy.