Does your explorer-mountaineer have an under hood whine, squeal, chirp, squeak,squeaking, whinning, bird chirp,sqealing, whirring, noise which tests your skills?
Well, it could be the camshaft position sensor drive unit-or cmp synch drive
Remove serpentine belt, run engine briefly, if noise persists with belt off, this is your noise. Camshaft position sensor- CMP synch drive shaft, which is notorious for failure on V-8 engines.
Since the noise is sometimes intermittent, you may want to leave belt off and perform test several times at 10-30 minute intervals, running engine only briefly each time, < 1 minute
If you are satisfied the noise isn't present without belt, rotate each pulley, and idler by hand. This should find any front engine bay, accessory drive, serpentine noise you encounter.
I hope this helps. Video of Camshaft position sensor squeaking below
Thanks to
yakuza76 for taking the time to make a you tube video for us--
http://www.youtube.com/watch?v=tpToVe0i-8k
Fix it by reading this first
http://www.explorerforum.com/forums/showthread.php?t=89670&highlight=camshaft+position+sensor+tool