Serpentine belt thrown twice on a 1988 C1500 5.7 350 Silverado

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Slade88

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I replaced my belt about 2 years ago after a smog pump delete. I never had any problems with it and never noticed any out of the ordinary wear and tear, a couple days ago after driving through a rain storm and going through several giant puddles that made my truck look like a boat I noticed my belt squealing when I started it up to come back home. The noise persisted when I got home but I figured it was just some water or something like that. I sprayed some water on the belt and the noise would stop for a bit. The next day I drive about 6 miles and the belt starts making a clacking noise, it sounded like it was coming from the belt tensioner which seemed to be shaking. I figured worst case scenario id have to replace the belt. I drive 12 miles to take my girlfriend to work and as we pull into the parking space it throws the belt. It stripped about 1 of the ribs off, no crazy damage. I then send a friend out to get another belt we install it, and the belt tensioner does not seem to want to move up and out of the way with just a socket turning it, its never done this before. The belt tensioner pulley has no resistance and doesn't make any noise when turned by hand, my alternator pulley gives a bit of resistance and makes some noise. My power steering pulley has less resistance then the alternator but makes a little noise when turned. My water pump pulley and clutch fan give a little resistance and noise as well but non of this seems out of the ordinary for my truck. My AC pulley gives no resistance with the clutch out but when I push on the clutch bearing to activate the AC compressor it gives a decent amount of resistance that makes it hard to turn by hand. My AC pump is original from factory and makes alot of noise when I turn the AC on, it literally shakes the truck. When we turned the truck on with the new belt it jumped off the crank pulley, water pump pulley, and tension bulley by about one rib. I shut off the truck and got everything flush again thinking we routed it wrong, then when I start the truck after the "correction" it hops off track instantly. I got the truck towed to my garage and am now wondering what to replace first, the engine starts easy too so I know its not seized or anything awful like that. Thanks!
 

HotWheelsBurban

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I would start by being sure the belt is the correct one ( different alternator sizes have different belts), but the tensioner and idler pulley are the likely suspects to me. Good luck and report back with the fix; you may help someone else!
 

tpass

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I would start by being sure the belt is the correct one ( different alternator sizes have different belts), but the tensioner and idler pulley are the likely suspects to me. Good luck and report back with the fix; you may help someone else!
yep, tensioner, mine seized up and threw the belt... good thing it was at idle.

I would go ahead and do the belt, tensioner and idler pulley all at once.
 

454cid

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You might verify the water pump pulley is spinning true. They slide on and off pretty easily if the clutch is removed and it wouldn't be hard to get something in between the pulley and flange.

Idler, tensioner, and belt would be a good idea, as mentioned. I had a idler go when the truck was still newish, but the tensioner lasted and lasted. I finally replaced just the pulley on the tensioner, but I have the whole assembly to put on it, sitting on my parts shelf. On the flip side the tensioner on my dad's old 96 seized.... not the pulley, but the arm. I thought that was weird.
 

HotWheelsBurban

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Good point about the water pump pulley. That's not something that happens often, but it only takes once....check other accessories pulleys for spinning true and straight too. Serpentine belts don't take much to get them out of whack.
 

User_name

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Look at the power steering pulley and make sure it's pressed on the shaft all the way. I had to replace the pump on my gmt800 with the 4.8 because the pulley walked forward. Guess the shaft was worn. That truck does alot of high rpms and hard takeoffs. The 4.8 in the single cab is a fun little motor for such a small displacement. Tough little bugger too.
 

Schurkey

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the belt tensioner does not seem to want to move up and out of the way with just a socket turning it, its never done this before.
You already know the tensioner is defective. Replace it.

when I push on the clutch bearing to activate the AC compressor it gives a decent amount of resistance that makes it hard to turn by hand. My AC pump is original from factory and makes alot of noise when I turn the AC on, it literally shakes the truck.
You already know the A/C compressor is defective, replace it.
 
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