Have a 2009 F550 with a 6.7L diesel. We have found oil in the water and we have to keep adding water but see no leaks. I will also run hot.

Blown head gasket or cracked head?

Is it still under warranty? If not, check you oil cooler. Check to see if you have water in the oil since you're lossing water somewhere with no visible leak. The oil cooler is most likely the oil in the radiator issue. Check both the engine and transmission for water, it's going some place and those are really the only 2 places it could go without a visible leak. Borrow or buy a radiator pressure tester, while it's cold you can build the pressure up and it's easier to look and find while the engine is cool.