95 Blazer 4 door 4wd. My belt was old and worn so I replaced it. When I put the new belt on, within a day or two a kind of chirping noise started to come form under the hood. Since it was a new belt, I thought it might be tensioner, so I got a new tensioner put on, but it didn't help. I said no big deal, probably a defective belt and exchanged it for the same one. Same thing happened again. So I bought a higher priced dayco belt this time. But the same thing just happened again. After spinning each pulley back and forth, the only one making noise is the alternator pulley, but it's when I spin it counter clock wise (when the car is running the alternator pulley spins clock wise). Is it possible that it's the alternator pulley causing this problem, if so can I get the pulley by itself, or do I have to buy a whole new alternator. Any advice would be great, I don't feel like getting an alternator unless it's absolutely the problem, because the electronic return policy at parts stores. Thanks

 

If the noise is coming from the alternator, I really doubt it is the pulley that is causing it.

As far as belts go on these 4.3L engines, I found out a long time ago to only use the Goodyear Gatorback belt. For some reason the belt routing and pulley diameters lead to belt noise on these engines and the gatorback's 'tread' pattern on the grooved side of the belt allows the belt to bend/flex more. I have cured a lot of noisy accessory drives with this belt.

 

Thanks for the advice! I will look into this right away. Hope your right because then it'll be a cheap fix.

 

I had that problem on my 98. Ended up being the idler pulley between the alt and a/c compressor.

 

I have the same exact problem with my 2000. Only I did my Idler pulley, tensioner pulley, and alternator, and I'm only on my 2nd chirping dayco belt. I think I have an oil leak getting on it though, or grease from my axles. I have been putting a very small amount of rtv on it when the chirping comes back, and that seems to fix it for a week or so, sometimes less . I think ill try this Goodyear belt though

 

also most serpentine belts have a directional arrow on them make sure it is going in the direction of rotation

 

I have a 1997 blazer and I just had the same thing going on with my blazer I put a new gates belt on and it did the same thing, A friend of mine told me that I had pulled the tensioner up to high so I went back and pushed the self tensioner back down and let it tighten itself and you cant hardly here the blazer.

 

I ordered a gatorback belt online yesterday. I'm gonna take the dayco one back today and wait for the gator. I'll give an update. Hopefully it works, if not I'll try some of the other suggestions I'm seeing in this thread. Thanks for all the ideas everyone.

 

Update. Sorry it took so long. So I got the gatorback belt and I also got a new idler pulley for the hell of it. So all together so far it's my 4th brand new belt, a new belt tensioner, and a new idler, and the problem still hasn't gone away.

Also, the chirp has changed to a whistle and it's only when I'm pressing on the gas pedal. No matter what speed I'm at 30mph, 60mph, etc., as long as the pedal is steady there is no noise. As I stated before, when the belt is off the only thing making a noise is the alternator pulley. Luckily my friend has a used alternator that's a perfect fit for my car. I'm gonna get it put on tomorrow and find out if this is what has been annoying me.

Any other ideas if this doesn't work?

 

Check the harmonic balancer. At idle look down at the balancer and if it is wobbling....even a little....that will more than likely be your problem.

One other thing you can try....get a bar or soap...AND BE VERY CAREFUL!!!!!!

Place the bar of soap on part of the belt...ie side...for a few seconds....listen for the squeak/chirp...if it continues touch the soap to the grooved side of the belt....listen....still chirping?? If yes apply to the backside of the belt.

if the sound goes away while applying the soap it is a belt/pulley issue.....if the noise continues then it is a bearing issue....oh, and the soap washes right off and will not hurt the belt.