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This is a really classic and common old car problem. I see it all the time but this is the first time it's started happening to my own car.

Basically when I first turn the car on, there's instantly a pretty horrific squealing that sounds belt-related, and develops to an even higher pitch as I pull out of my parking spot before cutting off as I straighten out and drive away.

Thereafter, there's just a slight squeak you can hear in the engine when it idles or I'm traveling at a low speed.

What could be the issue? I drive a 97 Subaru Legacy. The main belts are brand new.

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Does it sound like this? – Bob Cross May 6 '14 at 16:01
No. Squealing continues after engine is started and until car is fully in motion. – Aerovistae May 6 '14 at 16:11
Great help! Never done this before, but found it easy to fix my screeching car problem easily through your guidelines on my Kia Rio Lx. Cheers. :) – Ana Jul 16 at 2:59
up vote 16 down vote accepted

It sounds like your alternator has not been tightened enough and the serpentine belt is slipping because of it. Since you have new belts on your engine, this is probably about the only thing which it can be. If you press on the belt with your thumb at the center of the long portion of the belt (between pulleys), you should get no more than about 1/2" inch of deflection. If there is more than this, it's too loose. Here is a picture of where you should tighten it at (I believe this should look like your engine and belt setup):

enter image description here

To tighten, loosen the two bolts, circled in red, then turn the yellow circled bolt clockwise to tighten the belt. Don't forget to tighten the two red circled bolts after you tighten the belt.

If, after you tighten it up it is still squeaking some, get some belt dressing for it. Belt dressing is a spray on treatment you put on the rib side of the belt.

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Wish I could give this ten upvotes. Even if it turns out not to be the problem, it's just a great explanation and guide. Kudos. – Aerovistae May 6 '14 at 16:58
Thanks for the kind comments. I was just lucky this pic was available online. Without it, it would have been a lot harder to explain. – Pᴀᴜʟsᴛᴇʀ2 May 6 '14 at 17:06
I wonder why tensioner pulleys aren't more common. It is really annoying to have to adjust the tension of the belt with the alternator position. – Zaid May 7 '14 at 9:16
@Zaid ... Space limitations is probably the main reason. They are used on most every system I've ever seen. Was actually surprised this Subie doesn't have one, but again, space is a premium here. – Pᴀᴜʟsᴛᴇʀ2 May 7 '14 at 10:08
It seems this actually isn't the problem! The belt has almost zero deflection. – Aerovistae May 17 '14 at 17:50

It could be cause by loose belts. I had some squealing when I started my car, used belt conditioner, replaced the belt, and it still squealed. So I retightened it twice until finally it stopped squealing the third time I tightened it. I had been afraid of over-tightening it, but had under-tightened it repeatedly.

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Hi tman, and welcome to Motor Vehicle Maintenance & Repair and Stack Exchange. We tend to like answers that add something substantial that has not been said previously in answers to the question. Your answer seems to mostly repeat what is said in Pᴀᴜʟsᴛᴇʀ2's almost two years old answer. Could you perhaps edit your answer to make it more distinctive in this regard? – Michael Kjörling Apr 15 at 14:36

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