I think the top center (not ribbed) is also an idler.
top left - alternator
top middle - idler (smooth)
top right - idler (ribbed)
middle left - tensioner
middle middle - water pump
middle right - power steering
lower middle - crankshaft
Does that sound right?
You might want to pull the belt and manually spin all the pullies. My guess is your water pump is squeaking, but that'* because that is what happened on two of my cars recently.
Make sure its not the belt slipping and making the sound you hear.
Last edited by 2kg4u; 04-11-2011 at 03:30 PM.