Serpentine belt whining & sliding off.

[MJRemi]

I test drove the 88 the other day after tightening up some hose clamps. After about 2 minutes of driving I heard whining from the engine. Went back home and opened the hood to see/hear the problem. The belt was the culprit and it was pretty loud. After shutting off the engine I could see the belt was sliding off the pulleys toward the engine block. The water pump pulley looks to have some small dents around the inside edges. I think I can figure out how to re-seat the belt but what causes the sliding and how do I prevent that in the future? Also, is it difficult to replace the damaged pulley or should I hire a pro? I don't want to drive very far with the belt slipping but there is a shop about 3/4 of a mile from my house.

[wallisek]

Sounds like you already diagnosed the problem. Easy job to replace the pully as it should be held in by four studs along with the fan and clutch.

[Timmaay]

I had a similar problem and it turned out that the harmonic balancer was separating and causing the belt to be pulled sideways across the water pump pulley. Creating and extremely annoying whine that I didn't diagnose correctly for two water pump replacements. :thwak:

[MJRemi]

I had a similar problem and it turned out that the harmonic balancer was separating and causing the belt to be pulled sideways across the water pump pulley. Creating and extremely annoying whine that I didn't diagnose correctly for two water pump replacements. :thwak:

 

This engine was professionally rebuilt 1 year ago under previous ownership. Would the harmonic balancer have been part of that process? I saw a DIY on that so I think I'll try to inspect it when I replace the damaged pulley. All this "mechanical" stuff is somewhat new to me but with help from CC I think I can venture in past my comfort zone. :bowdown:

[Timmaay]

I had a similar problem and it turned out that the harmonic balancer was separating and causing the belt to be pulled sideways across the water pump pulley. Creating and extremely annoying whine that I didn't diagnose correctly for two water pump replacements. :thwak:

 

This engine was professionally rebuilt 1 year ago under previous ownership. Would the harmonic balancer have been part of that process? I saw a DIY on that so I think I'll try to inspect it when I replace the damaged pulley. All this "mechanical" stuff is somewhat new to me but with help from CC I think I can venture in past my comfort zone. :bowdown:

 

I don't know if that's part of the process. Does the balancer pulley look new? The two halves of the pulley should be flush with each other and the rubber in between should be in good condition. The pulley should not wobble while the engine is running.

[MJRemi]

I was able to get the belt pulled back onto the pulley with some effort. It seemed to stay put during a short test drive. I'm taking the truck into a shop to get smogged so I'll have them adjust the belt tension to spec. Thanks to all for the help!