Crewcab is overheating a little. At around town speeds (under 50) it stays around 200 like its supposed to. At highway speeds it rises to ~220 and stays there. I replaced the radiator and thermostat today and its still doing it. I drove 4 1/2 hours with it running at ~220 and it didnt seem to cause any problems, but it has always held 200 with everything working. The only other things I can think of are the fan clutch and water pump. I replaced the pump around 2 years ago and it isnt leaking but I've never messed with the fan. Is 200000 hard miles a reasonable service life for a fan clutch? Is there a way to diagnose it for sure?