I found this site while searching for some answer on solving an issue with the serp belt on my car. Hopefully someone here has some helpful info on the problem. I have a 1998 Pontiac Grand Prix GT with the non supercharged 3.8 motor. Ive had the car since new and never had an issue with the belt. Recently every time it rains the belt slips off . Ive replaced the belt and tensioner and Ive have a couple mechanics and the dealership look at it . So far no one can find a solution to the problem. Id like to find a solution to this problem cause other than this problem the car is in great shape for the age and mileage. Any help/info is greatly appreciated

Are you absolutely positive that you've got the right length belt? Even if it'* a few centimeters off, it can cause slippage.

I've seen parts managers at the dealer and counter boys at the box auto stores just grab something that'* really really close to get the customer out the door and out of their face.

As far as I can find the belt is supposed to be I think like 93.5" . I measured the belt and its 93.5". I didnt go any further than that .

Are all the pulleys spinning like they should, and are they all on right?

As far as I can tell. They all appear to be spinning straight not wobbling.

There are two belts for a 98 GP with the the non-*/c'd 3.8, a 93.5 inch and a 93.0 inch. The 93.0 is referred to as first design, and the 93.5 as second design. I do not know where the breakpoint from 1st to 2nd was, but I am willing to bet you need the 93.0" belt.

If that does not work, auto stores carry a sticky spray specificially to correct belt slippage. I would get a 93.0" belt if I were you.

Did you use a Dayco tensioner, by any chance? I bought it because it was the cheapest one I could find, and it caused my belt to constantly fly off in the rain.

Try navigating a NYC traffic jam during a downpour with your belt coming off every time to you hit a puddle. Traffic hated me. After that, I bought an AC Delco tensioner, and couldn't be happier.

I'll have to check and see if I can find the shorter belt . Im going to a local parts place after work tonight hopefully they'll know .

signofzeta I think I did use a Dayco tensioner. Like you said it was cheap and it was the only one the parts store had at the time.

Im going to start with a shorter belt if I can find it. If that doesnt work then Ill have to try the Ac Delco tensioner

If you end up replacing that tensioner with AC Delco here is the one you need, Amazon has it the cheapest I have seen it..

I checked the pulley'* this morning and as best as I can tell they are spinning true. None felt loose so I think that part should be good. I went to a local parts place yesterday after work and was able to find the shorter belt. I put it on today and it seem tighter which is good. I hosed the front of the motor down and couldnt get the belt to slip off so I have a good feeling its been fixed. Thanks everyone for the help