Already got it replaced ($250) on my truck (which has about 90k miles), but what's "haunting" me is should you replace things like that just because they make a squealing/screeching/.... noise? At the time, i just listened to the mechanic who said i should replace it (because "bad things can happen if it dies..."), and he said it couldn't be fixed because it's a "sealed" part. The noise wasn't so loud as to really annoy me, but it was fairly noisy. But who knows if a noise like that is really a predictor of failure...is it like a 3- fold risk of breaking down within a year, or what? It seemed to definitely be the fan clutch making the noise, since when he twirled it around with his hand, with the engine off, it made the noise .
Now that it's "fixed", the truck has a new "feature" (that i've read about...other people seem to have this problem).....The first mile of driving (at under 30 mph) has that roaring sound....and the truck never did this before....but from what i've read, that's not really a mechanical problem, just a "feature" of some of the cooling fans.
p.s. i also replaced the serp. belt (after only about 12-13000 miles (but 3 years), because it looked a little bit glazed (and some people said it looked almost already to replace). .