T noise you hear is the clutch fan kicking in. In the am it unlocks because it's cool. When it reaches a certain temp under the hood, it locks back up so the fan spins faster. It's notmal. As far as the engine temp, if it is running hot, you may want to have the cooling system flushed. I would say the thermostat, but you mentioned it runs normal without the ac on. Actually, it wouldn't be a bad idea to replace it too when the system is flushed. They are cheap.
Let me know if it helps.
Joe
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Sunday, June 28th, 2009 AT 3:33 PM