deisel fuel in radiator

[Waterloo]

Injector cup failure? Maybe when the new injector was installed? And that fuel mileage sucks. Have you done an EGR tuneup? And heating up, I wonder if they replaced the oil cooler and thermostat when they did the in frame? I would also see if you have a new head on that motor and not a reman. There is a code on the side of the head somewhere, stamped into the metal.