First: Check to ensure that you have not sucked a bag or something up in front of the radiator. These things are bottom feeders.
Second: Check to make sure that the rubber hose(drivers side) that runs from the brake booster.
Make sure that everything that is rubber or plastic is away from the exhayst manifolds.
Last: Check your serpetine belts. There is one for the engine of course and there is one or the AC. Make sure that they are straight and true and that everything that is supposed to spin, spins.
One more thing is to check the harmonic Balancer on the end of the crank and make sure it is not warped. It consists of the balancer, a bubber ring, and the outside ring where the serpintine belt runs. The rubber has been known to go bad and the thing wobbles rather than turns. If it coes out completely there can be quite a bit of damage done under the hood to the engine.