New serpentine belt squeaks at startup (idle, Nissan, noise, 1998)

[JBPisgah]

My new serpentine belt gives a chirp/squeak for a second when I start the car. I've guesstimated the correct tension by the turn belt 90 degrees test, and it seems right, but there so little space it's hard be sure. I've been cranking it tighter by a quarter turn on the adjusting screw every day. I cleaned the alternator, water pump, and idler pulleys, but still the same noise. The belt never makes any noise after startup. The old belt made the exact same noise at startup. Any ideas? Thanks.

1998 Nissan Altima,
Belt runs the PS, water pump, and alternator, not the AC. Noise still happens when the AC belt is removed.
Belt tension adjusted manually by set screw on alternator.

[SAAN]

Sometimes when that belt is replaced, it messes up the pulley or it might be slightly out of alignment, but when that normally happens, its constant and not for a second. Other symptoms Ive seen cause that were worn timing belts that cause a loud squeal on start up and goes away after a few seconds.

SO it could be the tensioner bearings, water pump bearings or worse case worn timing belt/chain.

[ukrkoz]

Maybe it's not the belt? Maybe it's actually one of the bearings? WP ones tend to do this.

[mclasser]

New belts loosen up during break in and often need re-tightening. Just tighten it until the squealing stops, quarter turn at a time. For serpentine belts, 1/4'' deflection is the sweet spot.