Engine/Transmission (1994 - 1998) Serpentine belt, tensioner pulley...something broke.

[Hogan]

This is actually on/for my friend's truck, who I was following when it happened...



After driving for about 30 hours straight (Moving from CA to AZ) on a new belt, we were about 1 mile from his house when *thud*, GEN light comes on, tach goes to 0, and a bit of smoke starts coming from under the hood. We pull over and take a look, the serpentine belt got shredded and part of it wrapped around the crank between the pulley and block, which before that it snagged the transmission cooler lines and ripped them off (At the quick disconnects, they just needed to be snapped back on) and something else ripped the tach pick-up from its bracket. It's still attached to the wires, though, just dangling there.



So as I'm looking things over, trying to figure out what happened, it hits me... something is missing. The belt tensioner assembly is gone...completely. The bolt in the middle that holds it on was sheared off, so now it's flush with the bracket. I never did find the bracket.



Question is, what happened? My guess is that the belt ended up riding off the edge of the tensioner and got between the pulley and bracket, which just ripped the bracket off and shredded the belt. There was a spot on the side of the belt, just before where it broke, that looked like something caught it and pulled it off, but I just don't know. Everything still attached spins freely.



Could a worn idler pulley have caused this? The truck has 165k miles on it.



Any help on what could've caused this would be greatly appreciated. Can the tach pickup be had from a Cummins dealer? Any idea on price?



What a bummer...



On a side note, my truck has 173k miles... I'm guessing I should go out and check my pulleys for play so I don't suffer the same fate.

 

[Cooker]

I imagine a worn idler pulley with a lot of play in it could have caused this? There is an aftermarket pulley available with a replacement bearing. It might be a good PM install, but this is the first time I have heard of something like this happening.

 

[illflem]

Here's a recent thread from 24 valve that addresses the problem - https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=72258



I've never heard of the tensioner getting ripped off but have seen a fan and radiator torn up from a flying belt.

 

[Hogan]

Originally posted by illflem

Here's a recent thread from 24 valve that addresses the problem - https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=72258



I've never heard of the tensioner getting ripped off but have seen a fan and radiator torn up from a flying belt.

Thanks.



I'll make sure he checks the alignment when he gets a new tensioner and also suggest he get the heavy-duty idler since at this point it's insurance against a repeat of the problem.



BTW, the belt looked like it was stretched until it broke, which makes sense about the tensioner breaking off since the belt got wrapped around the crank quite tightly. Too bad the tensioner is MIA. Oh well. Luckily it happed a mile from his house and not out in the middle of nowhere at 4am like we had been that morning.

 

[Hogan]

While inspecting my own truck...

While I was doing some checking on my truck today, I had the engine running and took a look at the idler pulley. It wasn't crooked or wobbling, but it did have maybe 1/5th inch or less of horizontal movement on the shaft as the engine was idling. How much of this movement is acceptable or should there be no movement?



Thanks guys...