Throwing belts

[Piece of Work]

3 times in the past week the alternator belt has come off, not broken. The first time I replaced it, the alternator was squealing loudly, had the alt. checked, low output, so I upgraded from a 1 wire to a three wire 94amp. At first it seemed fine, but then threw that belt too. I checked the pulley alignment and everything is good. no noises, no pulley wobble, nothing to suggest a problem. Replaced the belt with a different brand and it came off again. Belt tension is good and all looks well but this keeps happening. Any ideas why?

I can't afford to upgrade to serpentine. It's a 350 with alt. on the pass. side, A/C on drivers side. A/C belt doesn't come off, only the alt. belt.

[cdowns]

i'd check your pulleys real good to see if they are spliting and widening the pulley groove causing the belt to run too deep into the pulley causing the belt too come off

[Piece of Work]

Checked the pulleys, good and clean, no splits, dents, debris, or cracks.

[Sinister]

How's the alignment on the pulleys? If it's slightly off, it'll throw belts.

[Piece of Work]

I checked them with a straight edge. This problem showed up all at once, after 500+ miles with no problems.

[Sinister]

Originally Posted by Piece of Work

I checked them with a straight edge. This problem showed up all at once, after 500+ miles with no problems.

I figured you would have. Sorry, I have no idea what it could be.

[AusMarty]

I had that exact problem, it had me scratching my head for a while, turned out to be the water pump pulley worn it looked ok but when you compared it to a new one the belt sat a lot taller in the groove

[Piece of Work]

It is very puzzling. Most of these problems seem obvious in hindsight, but finding the cause is frustrating. At least now that I have a 3 wire alt., I get a big red warning light when it comes off!

[Piece of Work]

All pulleys were replaced 500 miles ago.

[AusMarty]

P.S the sqealing you hear is from the belt slipping, so if your belt tension is correct the belt isn't making full contact on the pulley hence the noise
I thought it was my altenator for a while to but it turned out to be the pump pulley

[AusMarty]

Are the pulleys chrome ?

[Piece of Work]

water pump pulley is chrome.

[AusMarty]

It might pay too sand the groove with some emery paper to roughen it up, I would suspect the belt is slipping on the chrome, I have heard of this happening before

[Piece of Work]

Thanks for the suggestion, I did that this morning before throwing the 3rd belt. Keep the ideas coming.

[AusMarty]

Geeezzz!! I know how you feel, it's pretty frustrating, if the belt is sqealing it's definetley a contact issue or something is seizing up causing it to jump off, I would be guessing you have checked the water pump ?

[arkracing]

does the waterpump pulley have 2 grooves? - one for the Alt & one for the PS or A/C? or just one for the Alt?

I had a problem with a customer's vehicle, the crank pulley had a different diameter outer pulley and the w/p pulley had 2 grooves the same size. The belts were turning different RPM's and it would throw one of them every 500 miles or so.

[Piece of Work]

2 grooves both the same size pump & crank pulleys, pump is fine, no squeal after alt. replaced. Notched belt, haven't tried Top Cog style yet.

[berencam]

Even though you checked the alignment with a straight edge, i think you may still have a mal aligned pulley. It will probably be the alt pulley. Even though the top of the pulley may be lined up with your water pump pulley if you look at the pulley from the side, the lower part of the pulley might be further in than the upper, or visa versa. Like this \ as opposed to this |. I would recommend buying a new bracket assembly. They make chrome ones for less than 30 bucks at o rielys...