Yesterday I noticed that my electric fan was making a groaning noise as I entered my carport. I killed the engine and opened the hood. I spun the fan and it had no roughness at all. I cranked the truck and the fan was running smooth. This morning I cranked the truck and headed down the highway. Ten miles out I noticed temp gage heading to red. I turned around and headed home. The temp went from red back to normal several times. The fan was making a roaring noise but was working. It seemed that running down the highway at 70, the radiator would get plenty of air. Does the electric fan run all of the time? Could my louvers in front of the radiator be opening and closing or is the electric fan failing. ??