squealing belt, '87 300sdl
 

New Continental belt on engine now, less than 200miles since replacement. After removing old belt found idler pulley bearing on tensioner ok, water pump and alternator turn freely; the squeal, is the belt; using a squirt bottle, engine running, I can spray a little water on the underside of the belt, squeal goes away immediately but comes back soon. I don't want to use retail "belt dressing" to treat the symptom, would prefer to treat the source. Anybody know the source???

Source = Belt is loose

Its probably the tensonor. Is the idler pully perfectly straight? They belt should be damn near center on it. If not replace the pully.