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Serpentine Belt Won't Stay On

I have a 1991 Dodge Dynasty with a 3.3 Liter engine & the serpentine belt keeps coming off. I have replaced the belt,idler pulley & belt tensioner. When the road is wet or winter slush (it happened once in dry hot weather) the belt will ride off. Has anyone ever had a similar problem?

I think Chrysler had a service bulletin on that problem some years ago. Can’t remember what the fix was but think it was shielding from the water. The only time I’ve had that problem with a GM was when the water pump bearing wore a little allowing the pulley to cock and run the belt off. Just a little looseness was enough to do it.

Possibly a plastic shield broke off and allowing water to get in.

I don’t have an explanation or a solution, but I’ve had the same thing happen on the same engine in a Caravan in the rain. However that only happened once in 100,000 miles, and I’ve driven that car in plenty of rain. This event occurred at low speed, and car had only been running about 10 minutes when this happened. At the time, the car had ~290k on the clock, with a relatively new belt. I don’t know if the belt had been working its way off the tensioner at that point, had no reason to even think about it. The plastic shield was in place. On another occasion, someone who didn’t know better sprayed WD40 on the belt attempting to quiet a squeak (no, it wasn’t me, he did it before I could stop him) with the result that the belt jumped off instantly. You might also post on Allpar’s minivan section if you haven’t already done so.

My son-in -law had this problem with a 3.4 in a minivan. One of his pulleys was out of line from a bent mounting bracket but I don;t remember which one. I think he discovered the problem by parking next to a similar vab in the family and comparing the two.
I also know that I routed the belt wrong on my 2002 minivan and didn’t discover it for 20,000 miles until it started squealing again.