Originally Posted by Scndsin

I recently removed my "soon to lock up" air pump on my 5.8. While shopping for the plastic idlers (which had developed flat spots) I found that there were 2 different types available for the tensioner. 150s got plastic, 250s got metal which is what I bought.

Initially, I tested alternate routing the original belt. By going "over" the fixed idler, under the tensioner, then around the Alt, then back to the crank. This actually worked. However, the Alt would squeal for few seconds when first cranked and when put under heavy electrical load.


Since I didn't care for that, I took a length of 3/8ths-7/16ths heavy nylon rope, routing the rope under the tensioner first (after it comes off the AC compressor) completely by-passing the upper idler, then looping the Alt before returning to the crank.

I took the rope, hung it on a nail & stretched it out tight, then tacked another nail at the bottom of the loop. This gave me a length of 47-1/2 inside the loop which I doubled to give me a 95 inch starting point.

I used my locally owned parts house to source the belt. Took 3 trips, but finally wound up with a 96.08 inch belt that gave the best tension & no noise. After a couple hundred miles, I've had no problems.

This past weekend I did some work on a friends 93 Taurus. I found that the tensioner's idler has the same bearing diameter & depth and is ribbed & shouldered like the Alt pully. I plan on using this if I develop belt throwing issues.

Hope this helps someone.