Based on the history, I would look first at the fan to see if one of the blades is hitting the shroud around the radiator. Some of them have rather tight clearances and the shroud has to be adjusted very precisely, and keep in mind that engine-mounted fans, (vs. Electric fans), will raise up a little when the engine is under load.
The clue is to look for shiny or chewed up spots on the shroud or shiny spots on the end of the fan blades where the paint is rubbed off.
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Thursday, April 7th, 2011 AT 4:28 AM