My engine has had overheating problems on long uphills on hot days. The temp will rise to about half way been the 215 and red line marks. ( Around 230-235 degrees) I've heard the aux fan kick in, but never noticed a difference in the viscous clutch kicking in. Its always spun. Tried to stop it when hot and it spins strong. But I've never noticed it kick in loudly when under load like I've seen people say on the forum. I replaced the clutch and no difference. Changed thermostat, radiator cap, flushed coolant and cleaned between the radiator stack. Then I thought maybe it was the serpentine belt or tensioner. Changed the serpentine belt and the newer one was certainly tighter than the old one. And the tensioner took quite a bit of strength to release the tension, so it seems strong. However, yesterday on a long uphills it still rose to about 230. Any ideas what it could be? Next thing I can think to change is the belt tensioner. It's an $80 part and id like to not keep throwing money at the problem with no improvement.