Probably more than one reason but, I find sometimes if a few drops of antifreeze gets splashed on the belt it eventually squeaks no matter what you try to do to cure it except replacement.
Belt worn out, or loose.
Usually the accessory drive belt is faulty
If it's coming from the engine, it's a belt problem. One of your accessories might be out of alignment, or your belt could be going bad.
It will squeak
Belt is most likely loose and/or needs replacing
the belt its old or oil contamination on the belt or the belt its contaminated whit antifreeze
Take a water bottle or similar and drip water on the friction face of the belts.When the squeak changes you know what beltChange the beltBuy a good brand name belt, I recomend:The best alternator belt is a Goodyear Gator-backThe AC belt should be a Dayco or similar toothed V belt, But NOT a Goodyear Gator back.Take the time and care to adjust exactly as recommended by the belt manufacturer.
you need to get some belt dressing and spray it on the belt it will stop the belt from sqeaking and can be used for all belts you can by it at any auto parts store it is called Belt Dressing it is in an arisal can it works very well.
The belt will squeak until the coolant wears off.
This is likely not a belt squeak, but rather the idler pulley. In the belt routing area, there will be a pulley (either metal or plastic that the belt goes around which is not connected to any or device. Inside that pulley is a small bearing (about the size of a silver dollar. When the permanent lubed grease finally gives up, it will start to squeak or squeal depending on how bad it is. To test this, find this pulley and spray some WD-40 or similar lube into the area while running -WATCH FINGERS- !! If the squeak goes away temporarily, then this is likely the problem. You can also undo the serpentine belt and turn this pulley with your fingers - it will likely be rough or hard to turn.
What causes the a squeak in my showtime rotisserie
brakes or belts check those first. a bad belt can fool ya