Hello,

I'm at a loss right now and would appreciate some help. 1993 5.0L with factory A/C and 130amp alt (I think). The idler pulley snapped off, then chewed up the serpentine belt, so I replaced both. Autozone said it would be a 77mm pulley, and 99.5" belt. I put them on, and now the tensioner keeps making a clacking noise...clack...clack...clack...etc. For every "clack," I can see the tensioner arm going all the way to the left, and apparently hitting some sort of stop, which is what is causing the clack sound, then it moves right about 0.75" or so, and then the cycle repeats. From what I understand, movement of the arm is normal, but the belt is getting so tight it is ramming the arm to the left and bottoming out. So does this mean the belt is too small? Or is the tensioner too weak? To get it on, I had to pull the arm all the way to the left until it hit the stop, and it just barely slipped onto the pulley. The tension felt significant, meaning it took a lot of force to get it all the way left to get the belt on, so I think the tensioner is ok. The tensioner bearing seems fine, and it doesn't make any noise when I "flex" the tensioner arm with the belt off.

All other pulleys glide smoothly, and have no play on any axis.

I was researching this, and everything says 99.5"/99.4", but I found 1 reference to a 100" belt for use with the 130amp alternator (on rockauto's site). Is it possible that such a tiny difference (0.5") could be the cause of my problem? I'm thinking about getting a generic 100.5" belt, and seeing if that solves the problem. Or is it more likely that something is wrong with the tensioner?

Thank you for any help!

 

A 1/2” is a lot for a belt. It sounds like you had to hold the tensioner against the stop and were barely able to install the belt which is too tight. Too loose and the belt will slip. If I recall there is a scale and a pointer cast into the tensioner to indicate that the tension is correct. Personally I don’t waste my time just replacing the pulley. Tensioners do wear out so I replace the assembly. I take it that you lost the original pulley when it broke so you were unable to compare the new and old parts?

 

Correct, pulley was long gone. However one single strand of the belt survived. It is about 1/2" longer than the 99.5" one... I thought maybe it was old and stretched. Maybe I should try the 100" then. Thank you for the reply.

 

Just put on the 100" belt, and all is well. The 99.5" was indeed too short and causing the problems.