a water pump can be the culprit when you hear a noise like that. they typically make a grinding noise cause the bearings are wearing out. the water pump of course will make it run hot and could affect your heat. the idler and tensioner pulleys are an easy and cheap fix, probably the cheapest place to start. the ones for the V6 Commander were $16 each from Advance. I would start here since you already did the belt. The ac compressor usually doesnt make a lot of noise , they just lock up. are you losing any antifreeze ? The water pump should have a weep hole where you would see some oily/antifreeze seepage.