new drive belt yields nasty squeal

[Jimak]

My 1996 Explorer 4.0 SOHC had been running quiet and strong. Driving home last week there was a loud bang from the front end. I stopped and looked under the hood where I saw the serpentine belt hanging loose. I thought it had broken but on closer inspection it turned out the belt was fine, the idler pulley had fallen off and must have banged into something as it exited the engine compartment. I got a new idler and put it on with a new belt. There is now a loud squeal. All the driven pulleys seem tight and no wobble, belt tension seems fine. I have used various tools to (very carefully) apply loads to each wheel as it turns to try to get a change in pitch. No luck. Finally took a wood broomstick and slipped it down and against the fan pulley. A little pressure on this stopped the squeal. I drove it for a few minutes then it started again, then stopped again a few minutes later. The next day it squeals again. I would have suspected the water pump normally but they usually go slowly and get worse over time in my experience. No signs of leakage thru indicator hole on pump. Seems like it should be related to the belt change but I am stumped. Don't want to go in and do water pump and fan clutch without some input first. Thanks much for any ideas. Jim

 

[yavapaires]

I've never run into this problem, but, I would remove the belt and turn the fan by hand and see if there is any noise before doing anything else.

 

[71cutty455]

Did you compare the lengths of the old belt and new one? Maybe the new one is just a bit longer making it slightly looser which is causing slippage and the squeal. Just an idea.....

 

[Jimak]

I did hold them together to see if they were the same but did not stretch them out tight for a really close check. When I put it on I was surprised how little I had to ease the tension arm to slip the belt over the idler. The belt seems tight when I push against it. I will spend some time on it this AM and start by pulling it off for a better comparison to the old one. I assume the old one would have stretched slightly over time. I t was actually in decent shape and I replaced it just because I was in there. It just occurred to me I can simply try the old one again to see if it does the same thing to eliminate the new belt as the problem. If it turns out to be that simple I will feel dumb but relieved.
Thanks for responding. Jim

 

[SparkyJeff]

Welcome to the forum!

I've never run into this problem, but, I would remove the belt and turn the fan by hand and see if there is any noise before doing anything else.

+1 Yeah that,
Also, be sure the belt is positioned properly on all of the pulleys.
I've heard belts that are one groove off that shriek like a banshee, I've also seen long belts that are a groove (or 2) off that sound normal.

 

[Jimak]

Problem solved! I put on the old belt and it is fine. When they were both out I hooked the ends of both belts over a rod and pinched the other ends and pulled tight. The new belt was a good quarter inch longer. Doesn't seem like much but it took a much longer swing of the tension arm to get it on.

I live in a remote place and parts come by mail. I am surprised NAPA could have sent a belt so close but still wrong. I wonder if an on an earlier belt change someone had put on an idler of a slightly smaller diameter than stock.

I love the simple fix when I get it.

Thanks for the welcome and for the responses. We have had this car for about twelve years and have been very happy with it. I did have to do the infamous blend-door repair several years ago but a good forum tutorial with photos got me thru it in a few hours and its worked fine since.

Thanks again, Jim