Squeak/Squeal Under Hood

Dribble a little water on the smooth backside of the belt while the noise is occurring. If it changes, start by checking that the tensioner is keeping the belt tight. (Check that with the engine not running). The next thing normally would be to check the belt. It can have up to one crack per inch on the ribbed side. We can skip that since yours is new. The last thing is to determine which pulley is tipped or turned. Most of the time you can sight down from on top. If you look straight down, you should not see the belt peeking out on the lower pulleys. If you do see it off-center on a pulley by as little as 1/16", that pulley or the one right before it is tipped or turned. Most commonly that is an idler pulley. Tensioner pulleys are next most common but those are a little beefier to handle the repeated spring-loaded movement. Being off-center forces the belt to slide across the pulley as it goes around it. That is what makes it squeal. Water can act like a temporary lubricant and make the noise stop for a few seconds, or it can make the belt stick better and squeal much louder.

If you cannot see the belt off-center anywhere relative to where it rounds other pulleys, look for a pulley where the paint is worn off making a shiny silver area that is wider than the belt. That tells you the belt is running in a different location than it was before. When the squeal is a fairly new problem, look for a pulley where the belt is running on an area that still has paint o it. That paint would have been worn off if the belt had always been running there.