Chevrolet: Belt noise, grooved pulleys, chevy impala

Question
2001 Chevy Impala, 85500k, 3.8 engine. I got my serpentine belt replaced last week, now whenever I accelerate, there's a whirring noise coming from it. Did they not put it on right?

Answer
Kate,
    Generally if a belt isn't on right, it will squeal pretty loud. You can check though by looking at the belt and pulleys to make sure that the grooved side of the belt is contacting the grooved pulleys and the smooth side of the belt the smooth pulleys. (I've seen stranger things, it can happen.) The serpentine belts on those cars are pretty much designed to self-center on the pulleys, but check to see if they are running roughly the same place the other belt was.. usually the smooth pulleys will discolor slightly where the belt runs consistently. If I'm understanding the noise right though, it sounds like it could be an idler pulley or tensioner. When the bearings go out on them they can squeal, but sometimes make a whirring noise. You can check this by finding the two smallest pulleys and trying to move them laterally to see if there is any movement that would indicate a bad bearing. Sometimes when you have a bad belt and get a new one installed, there is a "break in period" where the belt seats it's self and conforms to the pulleys, and occasionally there is a film build-up on the pulleys that causes the belt to slip a little under load. You can get a can of belt dressing from your local parts store and spray on the belts and see if the noise goes away. I would check, or have checked, the tensioner and idler pulley sooner rather than later though, because when the bearing in either one goes it will sieze up and burn the belt, and could leave you stranded. That said, I own an 01 Impala with 84,000 miles on it and my power steering just started making noise, and it makes a sound like an older car would when you bottom out the power steering when I accelerate. I would check the aforementioned things just so you don't get stranded somewhere, and if that doesn't net any result, let me know and I'll try to get into it a little deeper. Good Luck!