Couldn't figure out which accessory was screaching on my 331 fox body LTD.
Stethoscope indicated it was the idler pulley. Replaced that, still same noise.
Next did the AC compressor bearing, as it appeared to be right in that area
(either idler or compressor).
Vid below is after idler and compr bearing.
Back in the day, there was 2 or 3 V-belts, you could at least take one off at a time.
Not with serp. I did take the blower belt off, as that makes a nice blower whine
(even though you could easily hear accessory screach noise over it).
So removed belt (again, UGH!!) and tried rotating by hand, the only thing that made any noise
was water pump, as it just about came to a stop.
But especially with a blower on this motor, the water pump is a BIG job, so I wanted to be sure.
So how to get accessories to spin at speed, but one at a time.




Worked pretty good, ordered a 32" belt, which will be an effective 16" "length". Hard to get it to stay on serp pulley on drill, "that" far away with longer belt.
Water pump was not it, it was metal idler pulley, bad new one I guess. I went back to a new plastic idler pulley,
like the one it came stock with, no more noise.