already replaced one
is this a fan clutch problem?
http://www.youtube.com/watch?v=00Y-7q7N_5Y&feature on 2002 Chevrolet Trailblazer
seek diag and est
On a noise like that I would generally us a stethacope to pinpoint. Might try removing belt and inspect all idler bearing and inspect all pulleys. Check front balancer crankshaft bolt.