Serpentine Belt - What size?

[noelb]

I am using a Dayco 6PK2565 belt. last year I looked at the tenioner and found no movement whilst the engine was running I suspected a problem with it and so replaced tensioner. Still no movement whilst running. I notice that the tensioner releases fully back to the position it is in without a belt. I believe that even with a new belt it was this way. Should I go for a Smaller belt like a 6PK2555 - 10mm smaller.

[noelb]

Has anyone found that with the standard setup that the recommended belt is too big and you have had to use a smaller belt?

[redbird2]

I have ran into this several times what I found was that some where along the way the alternator had been changed out and they installed one with a smaller pulley and the original number belt and then tensioner would not keep the belt tight, I also had this issue with my signature truck as I took off the vacuum pump it took several tries to get one that works well on this set up.
The short of it is install the shorted belt and give it a try you won't be the first or last person to have to do this Good Luck

[noelb]

Thanks, I replaced the belt and alternator at the same time. The rear bearing on the alternator gave out 1300 miles from home!:( I was in a trialer park and had to wait two days for it and eventually when it didn't arrive and the take a taxi to the Mail sorting centre because they couldn't decide which zip code went where!:mad: The alternator was new aftermarket. I'll check the pulley sizes and see if that explains it.

[noelb]

Can't explain why the standard belt is too long but substituted for a 6k1005 which is 1/2 inch shorter. It just so happens that this belt is the standard belt on the latest 3.6 V6 in our GM Commodore Down Under! Now I don't have to pay through the nose for a belt. (not many 6.5's here) :)