I have the same issue, with the same year and model. I replaced the tensioner, the idler pully, the alternator, ac compressor, fan clutch, water pump, andd 3 belt. Same result everytime. I did notice thatm, and you may want to look at the pully on the water pump, and see if the belt is going crazy, with a wobble backk and forth on the pully. This is where my chirp is coming from. If I get a long screw driver and push the belt over where it is supposed to be, the chirp goes away. I took my explorer to the shop this morning, at ford. I will repost when they call me with the problem, in the mean time, check out the water pump pully and see if you belt is moving back and forth on the pully.
Monday, January 17th, 2011 AT 6:56 PM