OK folk, help me out here.... 87 Z28, 5.0/T5, just about stock. 4 belt system, car runs very well, only have to open teh hood for filter changes... I'm hearing a chirping for about three weeks, then teh one serpentine belt that runs alternator, water pump and crank snaps and dissapears. As teh water pump is driven by both ps and a/c belts, I limp home on Optima power. I change all belts (Goodyear on alt and smog, Dayco on ps and a/c-we didn't have all Goodyear like I was hoping), and sent teh alternator to my builder for testing. Alternator tests fine, so I re-charge teh Optima, bolt teh alt back up, and everything is quiet and good-voltage is fine. (alternator is a custom hi-amp build with good Delco parts, puts out close to 150 amps-carries my dual SPAL fans...) Teh next morning, I start it to move it out of teh way to put my other car in teh garage for service, and it begins to squeal even worse than it ever has. I immediately shut it down, put my mechanic's stethescope on everything, and only teh alternator is louder than I thought it should be. I took it loose, until teh belt was slack enough to not turn teh pulley, but tight enough that it wouldn't take out teh other belts by jumping rail. Teh obnoxious squealing is gone.....I take teh alternator back off, and send it down to teh builder (Tucson Alternator Exchange), and tell them to stick bearings in it regardless of their condition. They do, and I stick it back on teh car, and everything is quiet again. A couple days go by, and it starts squealing again...By now, I'm pretty pissed...luckily, it's an easy change. This time, I try a stock 105a alternator....I change it, and everything is quiet for three days. Meanwhile, I send my high-amp back to TAE, and have them dissect it...teh owner did it himself. After pronouncing it good, I change back to my high amp, and everything is fine for three days, then starts teh same squeal over again.... I don't know what teh heck it could be....only when teh belt is slipping is my voltage not perfect, and I've tried everything I know to find something wrong...it ran without fail for over two years with this alternator, and no problems that I could find. Teh Optima is right at 4 years old with no problems that I know of, starts like a champ, even after sitting for a while-has never been discharged. Teh dual SPAL fans are wired to come on with teh car, but never dip into low voltage sitiuations, or slow down when I turn on all teh other power stuff, like headlights or a/c. I have an aftermarket stereo, but not a boom-boom unit with lots of amps, etc. I haven't had any problems or done any maintenance, other than an oil change for over a year, so whatever is causing this is new.... Help me out before I buy a .99 for sale sign.....

Im no mechanic, but did you try Belt Dressing?

Shouldn't have to use it, that's snake oil.....I appreciate your suggestion, but it has never squealed before, meaning
something is wrong....BTW, you can use a bar of soap instead of belt dressing.....

not sure, did you say that is an old or new belt that slips sometimes?

Teh olds one slipped a little for a few weeks, only at start-up when cold, then after about three weeks, it snapped. Teh
new one does just teh same....

Well the belt dressing I have is great. It isnt slippery like soap would be, it is real tacky and gummy. And It kinda soaks into the rubber of the belt. If you get it on your hands it is really annoying and sticky for a long time. My serp belt never squeaks but I use it anyway to keep it nice and moist and in good working order.

Just be careful because I accidentally sprayed it on the alternator and is started making a weird noise. The day later it just stopped working and I needed a new alternator.

The grooves in the belt should not go all the way to the tips of the pulley and vice versa. Take a look at the peaks of the pulley, and the valleys of the belt. If they are shiny (in other words, the belt & pulley are making contact on those points), your pulley is worn.

Check all the pulleys - alternator, water pump, crank.

I had teh builder put a new pulley on my alternator, but I'll check out teh crank and water pump...

Are the pulleys chromed?

How tight are you pulling the belt?

No, all stock-I've tried loosish and tightish, doesn't seem to make a difference...

If you have access to a factory serpentine belt system with self tensioner, give that belt a twang. You can tighten your alternator at least that tight.

I sell auto parts, and have access to all teh belt tensioners, etc....I've put so many belts on in my life, I think I'll go to Goodyear heaven when I keel over...this one
is about teh perfectest tension, and easily done as I've ever seen..... I don't think it's a tension issue....