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belt or bearing squealing


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March 25, 2008
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'94 Ranger XLT
My wife's 2004 2 wheel drive explorer has a squealing under the hood thats driving her crazy and that in turn is driving me crazy. It squeals really loud sometimes and then quits, it gets worse during acceleration and usually quits after appr. 10 min's of driving. It's loud enough that it catches a stare if people are around. It's to bad to be a belt, and besides that about two months ago I changed the belt and also the tensioner, the replacement belt was the more expensive ribbed type belt. I have sprayed a can of belt dressing on it and that don't help. It don't do it all the time so it's hard to pin point the problem. It sounds to me like a bearing going bad, when I can catch it almost sounds like it's the alternator front bearing or maybe the idler pully next to the alternator. Has anyone else experienced a similar squealing problem with their 2004 explorer. One thing unusual is the day that I replaced the belt it actually threw the belt off while driving down the road and luckly my wife was in a good spot to pull over. I changed the tensioner also because I've heard that Ford has had problems with weak belt tensioners. Any suggestions?

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My '04 40k is quiet can't help you there but maybe someone else has the problem too.
On my heeps XJ/ZJ I fixed one squeal with a Goodyear Gatorback belt. Cheap one squealed too then I tried a Gatorback and it went away. My other Heep it was the Water pump that was making the noise, belt dressing didn’t help in that case.
What engine? How many miles?

Just turned over 75k and it has the 4.0 V6.

I would take off the belt again and spin all of the pulleys by hand. If one of them turns roughly then that bearing is bad. I think it is probably the idler pulley with the bad bearing though.


I'm going through the EXACT SAME problems with my wifes '04 Explorer.

4.0 engine, only 46k miles.......this is about to drive me NUTS!!!

1) I've run the motor without the squeals
2) Belt looked to be in OK shape, so like you tried belt dressing (no help)
3) I've changed the belt ($18 one from A-Z)
4) I replaced the tensioner (and pulley).....still squeals
5) Checked alternator, PS pump, ilder, etc........pulleys all spin freely and quietly
6) I listened with a long screwdriver (poor man's stethoscope) and thought the sound was strongest behind the water pump. New water pump.......still squeals.

I describe the problem to a local (decent) shop guy, and he suggests getting a better quality belt.

Today, wife took it to her friend's used car dealership and had their mechanic "diagnose" the problem - he says needs a new belt AND a new Harmonic Balancer.
Does this sound like a possibility?

HELP, Please!!!

Well, I'm a day and a half good now with no squealing. Here's something for you to check. I bought my explorer when it had appr. 1400 miles on it and so I know the belt had never been changed before the day that my wife threw it off back in April. I took the old belt to my brother-in-law at advance auto parts as he is the manager and has always worked on vehicle's so I trust him. He gave me the exact replacement belt that it called for and also matched the old one and I went and put it on and also replaced the tensioner because I always thought the OEM belt was to loose. Well yesterday while trying to figure out the squealing problem I looked at the tensioner and noticed that it wasn't really doing any work, it had very little tension on the belt and the belt seemed loose just like the OEM belt did. The tensioner has a stop built in the housing casting that will only allow the tension arm to rotate up so far and mine was against the stop. I had another car guy at work look at it and he said your belts to loose, so I removed the belt and took it back to my brother-in-law and asked him if he was sure he gave me the right belt and he checked the P/N and said yes thats the belt it calls for. It was 85.5" long, that was just to long so I took a 85" belt and put it on and it was better, it moved the tensioner arm about a 1/4" off the stop but it could still be better so I took it off and went and got a 84.5" belt and it fit perfect. Now the tensioner arm is in the center of the two stops and is having to work like it's designed to. The belt is running a lot truer and the whole engine is running better. I also replaced the top idler pully just in case the bearing was the problem. So all is good now I hope, she going to the beach in 2 weeks so I've got to get it right. Check your tensioner and see if working and keeping your belt good and tight.

Thanks, I'll double-check the belt length/size.

Wierd? The motorcraft replacement part is supposed to be 86.125 length. There are also 85.5 and 84.5 belts that show up for different Explorers.......I may try your solution.

We'll be able to tell if your belt length is ok by looking at your tensioner.

OK, thanks to some other folks on these forums:

I've deciphered the problem........the grooved outer pulley on the harmonic balancer has separated from the inner rubber dampening section and actually slid back towards the engine block. The belt then rode up and off of the grooved part of the pulley and has been riding on the rubbery surface of the dampening section for about two weeks.:eek::eek::eek:

Hopefully, her car is the ONLY one out there with this freakish problem!! Thanks to Al and Rusty for helping me figure this one out!

I'll post pics of the situation once everything is back in working order.