[Fulltiming]

Forest, my first suggestion would be to have the radiator steam cleaned on the outside. If this hasn't been done in a while oil, road dirt and other gunk can accumulate on the radiator and reduce the air flow. Secondly, when the engine is hot, I would start and the top left corner of the radiator with an infrared thermometer and go side to side then drop down an inch or two and make a pass the opposite direction until you get to the bottom of the radiator. You should see pretty uniform temps across the radiator and see the temperature slowly dropping as you get further down the radiator. If you don't see at least a 20 degree temperature difference between the top and the bottom of the radiator or if you see concentrated hot spots or cold spots you may need to have your radiator rodded to remove obstruction in the core.