I replaced the power steering pump on my van a couple weeks/months ago and just went ahead and replaced the belts while I was under there. Ever since then, the alternator belt squeaks occasionally. It's been between pretty cold lately ( 0 - 30 range), so that might have something to do with it, but it never squeaked when it was cold like that before. I've tightened the tensioner up a couple times and I literally don't think it will go any tighter, yet it still squeaks sometimes. The belt seems to be the correct belt as far as I can tell (looks just like the old one), but the squeaking definitely started as soon as I put the new belt on. Ideas? Is there some sort of break-in thing that I'm unaware of?

I have many occasions of this happening to me as well. On older cars, the pulleys get get glazed to a highly polished-like condition over the years. The pulleys are fine but the "polished" surfaces of the v-grooves against the rougher surfaces of the new belts can tend to squeak a bit, especially when it is cold outside. This squeaking can go away on its own over time but it can also get worse depending on the type and brand of belt that you have.

There is an easy fix for this. Be sure that your belts are tightened properly. Not too tight, as you indicated they might be now, and obviously not too loose. Purchase from your local automotive parts store a spray can of belt dressing. It's sometimes called belt conditioner. This needs to be sprayed onto the contact surface of the belts which is sometimes a bit tricky when they are already installed. The spray cans usually come with a spray nozzle tube. With the utmost care and caution, with the engine running, spray the product onto the belt side that contacts the pulley. First, see that you can get a good spray angle to any part of the belt, without putting your hands or the can dangerously close to other belts or the fan. While the engine is running, spray for a couple of seconds without moving and you will have covered the entire belt. The squeak should immediately stop.

If in doubt of your safety at all, do not run the engine. Simply try to spray the entire belt as best you can. You won't be able to get every part of it covered but it will probably be enough to take care of the problem.

I tried squirting some conditioner on it, but it didn't really seem to help all that much. Granted I can't really get a good angle on it without tearing the splash guards and wheel off. Nevertheless, I think I got a good coating on there. Still squeaks a bit.

I know pulleys can get polished a little bit, but I didn't think the alternator was all that old. I think I replaced it a couple years ago. Maybe I should take some fine grit sandpaper to the pulley grooves to rough it up a bit - when it gets warmer.

I ended up taking a dremel with a wire brush to it. Seemed to work out alright.

Emory paper would of done the same..was the belt oem?

Well, crap. Now that the alternator belt isn't squeaking anymore, the water pump and power steering pump belt is squeaking. I took a wire wheel to rough up the crankshaft pulley and the water pump pulley, but it's still squeaking. It doesn't seem to be affected at all by turning the steering wheel, so I doubt it's the PS pulley or crank (the RPM dips a bit when I turn the wheel, but no additional squeaking). It's definitely worse when it's cold outside, then gradually goes away as it warms up, so it's definitely linked to engine temp. I've roughed up the pulley and lubed it up good with belt dressing, but it's still squeaking away. The water pump was replaced not long ago and is free to spin by hand, so it hardly seems that the water pump itself is bad (no dribbling either). Other than to go buy a different set of belts, I'm at a loss.