Sorry jafer, you have that backward. V-belts will squeal when they're loose. They have to be forced to wedge down into the grooves to grip the sides of the pulleys. When they're loose, they won't do that, and when they're worn so thin that the bottom of the belt rides on the flat center part of the pulley, they'll slide over it and squeal. They can easily tolerate pulley misalignment by a lot. Just look at the older Chryslers that used two belts side-by-side on cars with factory-installed air conditioning. They had two pulley grooves on the alternator. If you used that alternator on a car without air conditioning, only one belt was used but you could mistakenly install it in the wrong groove on that double-grooved alternator. That put the belt out-of-alignment by over an inch, ... And they would not squeal. In fact, you'd never know it was routed wrong unless you looked at it.
Serpentine belts used on all engines today are not the least bit forgiving of pulley misalignment. The ribs have very little area to grip the pulleys individually, but when they all grip together, they develop the same force as a V-belt. It's the smooth back side that squeals when it is forced to slide sideways across a smooth pulley that makes the squeal. You can verify that by lightly sprinkling a little water on the belt while the engine is idling. If the squeal changes, the belt is either loose or one pulley is out of alignment.
Chrysler had a service bulletin in the mid '90s for repositioning the alternator on their 4-cylinder engines. The modification moved it one way or the other, as needed, to the side by as little as 1/32" to eliminate the serpentine belt squeal. Their fix will real simple and effective. Ford had six different service bulletins addressing serpentine belt squeal on their trucks, and a friend who is currently a Ford mechanic said none of their fixes were effective.
Dirt on the smooth side of serpentine belts also causes squeals. At the risk of someone getting hurt or poking out an eye, we used to run the sharp end of a flat file on the belt while the engine was idling to scrape off that dirt. The powder from driving a lot on dirt roads embeds itself into the belt and reduces its gripping ability. If you saw sparks jumping off the file, those were from tiny rock granules hitting the file. Once the rock chips were knocked off the belt, the sparks would stop. That solved a lot of belt noises more like a "pinging" sound; not so much a squeal. It's also extremely important to never use any type of belt dressing to try to stop a squeal. The belt is still going to slide over a misaligned pulley, only now with greater resistance and a louder squeal, and the sticky goo with hold even more dirt to the belt and aggravate that problem.
Belt squeal with serpentine belts is a big problem. Squeals from V-belts are very rare, but they always are easy to solve. Regardless, without more details from airesram57, we don't even know if it's belt squeal we're dealing with.
Friday, December 16th, 2011 AT 9:43 PM