Belt Squeaking on Startup - year old belts, new alternator...what could...?

The serpentine belts were replaced myself recently in January 2008, and changed the alternator in August 2008. Squeaking started only after I changed the alternator and placed the belts back on. I've tried tightening and loosening the belts and it doesn't seem to solve the problem. I notice sometimes that if the belts squeal for a bit and I (a) gun the engine or (b)turn the wheel fast, the noise will go away.



What's everyone got for a guess? Stiff bearing on one of the pumps? Bad Alternator? Belts still to new?
Belt Squeaking on Startup - year old belts, new alternator...what could...?
The alternator draws the most load when the vehicle first starts due to a lower state of charge when cold (the regulator is looking for some where around 13v).

You probably have build up in one or more of the pulleys, I have seen one instance where the pulley was worn out and would not cradle the belt properly.
Belt Squeaking on Startup - year old belts, new alternator...what could...?
Even some serp belts need to be TIGHT to not squeal on cold startup.



90's Jeep 4.0's for ex.



You should only be able to deflect the belt 1/2%26quot; or so if you push on it with 5 lb's or so of force.



If it's flopping around when the engine is at idle it's tooooooooooo loose
As a mechanic of 30 years I'd say that Don K is right on.
I'd take a spray bottle full of water and selectively spray portions of each belt one at a time. Then see if the squeaking immediately stops for a certain belt. If all the squeaking ends up coming from just the serpentine belt (when you spritz it with water, the squeak abruptly stops), then remove that belt again and carefully look at the ribbed side to see if any small shiny foreign objects are embedded in the ribbs. Clean the belt and also clean all the pulleys well. Then make sure the belt tensioner is properly tensioning the belt. Once you get the pulleys clean, you can always try a brand new belt and keep the old belt for emergencies. The water spritz test removes any uncertainty about whether it's a belt or bearing noise etc.
there could be a bearing going bad but i would rather think that the belt tensioner has gotten tired or just needs to be replaced
The alternator isn't tight enough. After the car is running for a half hour or so try touching the pulley on the alternator. Be careful, you might lose your fingerprints. If it's hot, then it needs tightening.
As a mechanic for many years I can tell you that %26quot;most%26quot; belts do not squeal at high speeds. Some will stop squealing after the warm up. Now to answer your question. The new alternator came with a new drive pulley on it.? What happened, is the new belt that you put on in Jan. wore down to fit the old drive pulley. If the groves on your old alternator drive pulley was even slightly wore, then the old belt will costume fit it to the old pulley. Now that there is a new pulley that has no wear on it, the old belt does not fit into the new groves. They are actually smaller, and therfore the groves on the new belt do not fit. I hope I am explaining this well enough for you to under stand what I'm trying to say. Change the belt and the squealing should go away. Good luck.