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My serpentine belt keeps shredding, the garage can't seem to figure it out they have checked out all the pullys and seem to think they are all ok.
"It is a 1994 sedan deville with a 4.9 engine
 

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If none of your pulleys is locked up, I'd guess either they are not all lined up properly ( out of alignment ) or your tensioner is bad.
 

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I had a 95 deville and it did the same thing. It was the tensioner pulley, it is or was, made partly of plastic (seemed like it was that) and it was cracking and breaking which let the pulley move and so did the belt which shredded it.

That was my experience anyway. I have a 1997 Deville and no problem there so far at 94k miles.
 

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Yeah, I agree. I think one of the pulleys/ideler is out of plane.
All of them should lie in a perfect plane, if not it will shred.
Fairly common, it can be fixed by adjusting or worst case shims.
 

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hey just to throw my 2 cents in if in fact the pulleys are all fine check the patern for of which the belt travels because the diagram that the pic on the hood shows is turned clockwize so in the picture the alt. tentioner pulley and pwer.str. pump are going down the right side of the diagram

i know u'll think that if its running the wrong patern the stuff will be spinnin the wrong way but it doesnt if the mistake was made like ours was check that easy and free to fix
 

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One more thing to consider is that one of your pulleys may be siezed. Be sure to spin the pulleys before you install another belt. But, I think odds are your tensioner or idler pulley is misaligned.
 

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If the pullies prove to be ok in all respects, be sure to check the water pump. I found out the hard way on my wifes 3800, that Dex-Cool will detiriorate a belt in short order (I suspect the green coolant will as well). In my case, the pump seal was leaking and the weep hole was directly over the belt. A tell tale sign was a line of coolant that was slung across the hood insulation by the spinning belt. I am not sure if the 4.9 lines up this way but check it out.
 

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if you are certain that the tensioner pulley and alignment are cool...as per
your previous post (its always a bummer after about two belts, and the guy
scratches his head...lol) The next place to look is special.

The front of the block has a yoke shaped plate mounted to it, upon which
all the ancillary devices...alt.,p/s pump, smog pump, etc. are mounted.

If you can imagine looking at the setup from the front, the center pins (capscrews) are placed into the block, the outer pins sink into the heads.

I would wager one of those outer pins (capscrews/bolts) is broken.

most of the time the idler pullet is the culprit, but it is another part of this
assembly if it fails rapidly in succession.

If your serviceman is unaware of this common problem with every GM block
made since the 80's I would give some serious thought to finding one with
some experience.
 

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how is the belt shredding, is it on the edges or does it look like the belt has gotten hot. if is on the edge look for something on that side of the belt. If it looks like its gotten hot then suspect a pulley, or ac clutch
 

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All of the above. But in my case it was the tensioner itself. All pullies (including the tensioner pulley) were fine or new, but the tensioner, which did still move when torqued on with a bar, was stiff enough to cause it to not self adjust when it was supposed to.
I don't remember every detail about how the shredding pattern went, but it didn't take long to ruin a belt. My first clue in fact was the under-hood insulater mat was being gouged in a nice neat swath by threads of the belt flipping around as the engine ran.
New tensioner fixed it. Good luck.

Paul
 

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I have the same proble, this is the 3rd belt. last one was done by the dealership. They also put in a new belt tensioner in a few months ago along with a new compressor. I hope they fix it this time correctly and for free. Just broke down a few hours ago. I'll keep you posted.

Gus
 

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My new serpent started deterioation and senior Cadillac mechanic found a solution.

He noted a stone chip in the A/C pulley , very very slight however every new belt you put on auto was in trouble in 5 to 10,000 miles. Took a file and dressed out the nick in pulley put a new improved belt on it and no more problems .

Eleminated a periodic squeaking belt at same time.

Look for a tiny stone nick in bottom pulley.. It is not very far off the road and no guard to prevent kick up stone. Glad I did not take a stone in windshield.

Sorry you are having repeat problems on same deal; you will get a solution at this great forum.
 

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Did you ever solve your serpentine belt shredding issue? I seem to be having the same problem. Replaced the tensioner, but keep eating new belts. Appears that all of the pulleys are off about one notch. The car has a long block in it and I'm wondering if someone failed to transfer spacer or something on he harmonic balancer.
 

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Make sure you get a Gator Back belt it has deeper grooves then the new belts their selling for the 4.9 engine. I was going through the same problem.
 

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I remember something on the 4.9 motor that one of the water pump housing bolts, or timing chain cover bolts was very close to the belt and caused the inside edge of the belt to shred.
 

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My 95 just shredded off while I was driving. Not fun driving home with no power steering. There was a missing rubber foot on the front frame that holds up the hood to the proper height.
The insulation under the hood was all gouged out. I guess the hood was resting right on top of the pulleys. I crafted my own foot out of some old rubber and I'm hoping that fixes it.
 

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The belt was chewed up on my 93 deville 4.9 this summer and when I went to replace it found the idler pulley wobbled and the whole pulley was moving side to side. I replaced the original 250000Km but had to omit the bearing dust caps that came factory because either they jammed the pulley when tightened or didn't allow for proper alignment I don't remember. Glad it wasn't the water pump because this is the best GM I have ever owned as far as keeping its coolant level and the belt is not showing any wear. I believe that I read somewhere here that a belt should never tear up under normal lifespan only if there is a misalignment or an unintended object coming into contact with the belt.
 

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Thats guys for everyone's tips! it all make sense! I do think its the Tensioner gone bad! this is my 3rd belt!:yup:
 
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