Why is my belt coming off?

nghtshd88

nghtshd88

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New motorcraft belt. Started the car after 2 days sitting and it sounded like a loud a/c clutch flipping on and off. I noticed the belt coming off the idler pulley and coming off a bit on the tensioner. The alternator pulley looks fine. Belt was in properly.

I heard some noise a bit of squeal and what sounds like bad bearings when cold. Balancer looks kinda wobbly or out of sinc. I really hope I dont have to dismantle the cooling system again I just did last week..... I also am feeling a bit of misfire or rough idle but only when cold, no noise from the pulleys when warm. Of course it just hit zero degrees 2 days ago.

20161216_105544.jpg
 
The comments below are valid, but this first: That belt routing looks very wrong. The belt should loop all the way around the tensioner. (Assuming this is the V8.)
http://deneau.info/ls/s6x~us~en~file=s6x35002.htm~gen~ref.htm


I think that if you have an 05 or 06, there is a good chance that your damper is failing. If so, be glad that you got this warning before total failure. Look and see if the outer part (pulley) is pulling out or away from the inner part. Also look for any wobble while the engine is running. The tensioner swinging back and forth can be a give-a-way.

Otherwise, make sure all the other pulleys (idler, tensioner, and water pump in particular) are straight and have no up/down or left/right tilt to them.
 
05 3.9 48k miles

That is the correct routing. Youre looking at the idler pulley not the tensioner. It is coming off the tensioner to a bit to but more so idler pulley.

Looking at it while running the harmonic balancer is wobbling a lot and looks to be sending the belt a bit of movement over the tensioner. I never really took note of how much it should wobble if at all? I assume if the play is between the alternator and damper it has to be one of them and def looks to not be the alternator. This just happened as soon as it got really cold outside.

I cant see any tilt in any. Its a bit hard since there is zero room and coolant pipes block most of it!

It sounds like the a/c clutch engaging when it kicks the belt around.

I can get the belt off to check for play in those two pulleys but if it is the balancer do i need to dismantle the coolant system again? How much do they run? Never had one go bad so dont know the consequences..
 
I see says the blind man...
The damper shouldn't wobble at all. (Do also check the AC clutch pulley, with the belt off.)

I think that the upper and lower hoses have to come off to change out the damper. I have also heard that the oil filter adapter should be removed.

The damper is part 2W4Z-6312-AA, and is $729. (I kid you not. I'd try to find a good used one on e-bay or from a local junkyard.) You'll need some specialized tools to get it off and back on.
You'll also need a new damper bolt, XW4Z-6A340-AA at $23. You're not supposed to reuse the existing one.
And, you'll need a new seal, 2W9Z-6700-AA at $17.

If you plan to keep it for the long run, I would go ahead and change out the timing cover seals and valve cover gaskets at the same time. You;d have to remove the damper and valve covers later to replace those seals when they start to leak. My 04 has a growing leak from the lower timing cover seal. I have heard of others with the same leak.
 
What a PITA. Its zero degrees out and dont plan on doing those seals. Zero leaks from them right now. Hopefully only one hose off I can do that..

What exactly are the specialized tools? Thought it was a bolt only besides the puller.

And if this one failed already Im not sure id want a crusty used one. Nor do I want to spend 730$ on a new one. Is the doorman one that bad? Despite the name Id much rather get an aftermarket one over user or new.
 
Never heard of a Dorman damper that fits the 3.9 before.
The seal on my 04 never leaked or seeped at all, until it did.
There was a bad batch of dampers from the factory. The good ones don't fail (well, within 20 years anyway).
There's a tool needed to correctly seat the seal. You might be able to make something with a long bolt, really big washer, and piece of pipe.
There's a tool (basically a really long bolt and washer) needed to reinstall the damper. Don't forget to add the sealant.
You need a good chain wrench to hold the crank pulley while you try to loosen the bolt. If that pulley slips (it will go the wrong way), then you will damage the timing chains and tensioners.
http://deneau.info/ls/s6x~us~en~file=s6x31010.htm~gen~ref.htm
 
nghtshd88 said:
... Is the doorman one that bad? Despite the name Id much rather get an aftermarket one over user or new.
Click to expand...

joegr said:
Never heard of a Dorman damper that fits the 3.9 before...
Click to expand...

I just checked again. I can only find a Dorman damper for the V6. The V6 and V8 dampers are different.
I did find an aftermarket damper for the V8, but it is $349. If I was willing to spend that, I'd probably go with the $729 factory one.
 
I'd double check the alignment of the tensioner pulley. Especially if you loosened/removed it to get the drive belt off to do the cooling system work. Most procedures call for loosening/ removing the tensioner. if you didn't get it back in proper position,,, and it is cocked slightly,,, this may be your noise. To double check the noise on the tensioner... VERY CAREFULLY put the end of a long flat blade screwdriver on the bolt of the pulley in the foreground of your pic. If you hear an amplified scraping/ grinding... the tensioner pulley bearing is bad. Buy a new tensioner assembly at that point.

I'm gonna guess,,, that you loosened or removed the tensioner when removing the belt,,, because that is the recommended proceedure. It's actually not necessary... and IIRC there is a notch/detent of some sort that the tensioner assembly lines into. If you don't find that notch... the tensioner will be mis-aligned... and can trash an already bad tensioner bearing... and cast the belt to the outside of the pulley.

I went through the cooling system rebuild a few years ago... and never loosened/removed the belt tensioner from the block. Yeah... it's tight,,, but it is possible to get the belt past the tensioner... so you don't have to loosen the tensioner.

Again... using a mechanics stethescope,,, or a long thin screwdriver as a mechanics stethescope.... very VERY carfully probe around to locate where the noise is coming from. Again,,, keep in mind that you will be working around rotating machinery... so watch what you are doing when probing. Oviously you won't want to probe around the crankshaft while the enging is running, (and it won't do any good to do the same while the engine is off).
 
04_Sport_LS said:
...Most procedures call for loosening/ removing the tensioner. ... because that is the recommended proceedure. ...
Click to expand...

What procedures, recommended by who? Certainly not the factory manual.

This is what the factory manual says "Rotate the accessory drive belt tensioner counterclockwise and remove the accessory drive belt. " There's nothing about loosening it or removing it, except in the procedure to replace the tensioner.
 
Well... I distinctly remember a few years back on this site,,, where People were loosening the tensioner to get the drive Belt off... be it for only drive belt replacement... OR work on the cooling system. IIRC,,, Some of them seemed to have problems getting the tensioner back in the proper position. Not wanting to deal with that... I managed to get the belt past the back side of the tensioner,,, by rocking the tensioner back and forth until the belt slipped past, (and yes it is a tight squeeze). Not knowing exactly what "nightshade" did... I gave my suggestions based on what previous posters dealt with,,, and how I did things.

Nightshade said in his last post,,, that all he did was change the belt. Your diagnosis about the damper may be correct... but if all "nightshade did was change a belt, (after doing the cooling system a week or so earlier),,, then I would suspect that something went FUBAR in the tensioner. A simple way to tell that... would be to gently probe around the tensioner mount or pulley,,, with a long screwdriver or mechaics stethescope.

Maybe instead of saying "most proceedures"... I should have said "many people". Sorry my terminology didn't match up with your mindset!!!!!
 
04_Sport_LS said:
Well... I distinctly remember a few years back on this site,,, where People were loosening the tensioner to get the drive Belt off... be it for only drive belt replacement... OR work on the cooling system. IIRC,,, Some of them seemed to have problems getting the tensioner back in the proper position. Not wanting to deal with that... I managed to get the belt past the back side of the tensioner,,, by rocking the tensioner back and forth until the belt slipped past, (and yes it is a tight squeeze). Not knowing exactly what "nightshade" did... I gave my suggestions based on what previous posters dealt with,,, and how I did things.

Nightshade said in his last post,,, that all he did was change the belt. Your diagnosis about the damper may be correct... but if all "nightshade did was change a belt, (after doing the cooling system a week or so earlier),,, then I would suspect that something went FUBAR in the tensioner. A simple way to tell that... would be to gently probe around the tensioner mount or pulley,,, with a long screwdriver or mechaics stethescope.

Maybe instead of saying "most proceedures"... I should have said "many people". Sorry my terminology didn't match up with your mindset!!!!!
Click to expand...

Taking off the tensioner would make reinstalling it nigh on impossible with belt routed. The only way to do it right is to release the tension on the tensioner like nghtshd88 did. I've done many serpentine belts over the years and have NEVER removed the tensioner; just used this to release the tension on the belt. It works beautifully (I didn't need any of the attachments).

image_16281.jpg

image_16281.jpg
 
I NEVER said to try and take the tensioner off with the belt still installed! But swapping the belt can be a b!tch when it comes to trying to get it behind the tensioner to get it swapped. At least a few people commented over the years... that they loosened the tensioner,,, to get the belt out from between the tentioner and the timing cover.

Nightshade said he swapped the belt by whatever process he used... and all of a sudden he is having noise and blet alignment issues. It is fairly common,,, that a new belt, (being slightly shorter than a worn/ stretched belt), will put extra stress on an old tensioner, and/or the bearing in the pulley. Seen it a bunch of times. Either the bearing trashes... or something in the tensioner arm falls apart.

Nightshade,

You may have diagnosed your your own problem in your first post. Might want to check out the A/C clutch assembly. There is a bearing in there too that could fail. Might have been on the way out, and the new tighter belt caused enough extra strain to cause it to fail. I still think there is a problem with the tensioner,,, because that would be the next pulley to the right, (towards drivers side)... and if something blew out in the tensioner that would be what's causing the belt to try and walk off the idler pulley.
 
Just wondering, isn't the tensioner's job to maintain the same tension over the life of a belt? If so, a new belt won't add more load to any of the rotating components.
 
04_Sport_LS said:
Don't forget the tensioner is spring loaded. The tighter the belt,,, the more the spring tension.
Click to expand...

It's really close to the same across the whole range of the tensioner. (It's a few percent stronger for a shorter belt than a longer one, but it's not much of a difference.)
 
I'll agree with what Joe said, (for the most part). The more resistance a spring "feels"... the more it "pushes back"... and as resistance is reduced,,, the less it pushes back. Springs can be either torsional or of compression type... but at the same time,,, they both exibit both characteristics, (in opposite ways). Take a coil spring for first example, (like for a strut or engine valve). The more it compresses,,, the shorter it gets, (in rod length, not diameter), as it fights against the resistance it feels,,, while it gets "fatter" in diameter. The opposite is true of a torsional spring, (twisted rod). The more it compresses... the longer it gets,,, while getting "skinnier" in diameter, (think Mopar and GM suspension springs of years past).

The spring in a belt tensioner is both compressive,,, and torsional by design. So it does "double duty". It grows in length,,, and reduces in compression AND diameter... as the belt lengthens through wear. It does the opposite when a new belt is installed. On top of this... since a belt is continuously revolving,,, there is a minor amount of continuous variation in tension,,, as the design ATTEMPTS to keep tension on the belt.

Either way... a belt tensioner has TWO moving parts. The pulley, (with a bearing inside), ... and the tensioner spring, (inside the tensioner housing), which is located around a revolving axis. Eventually one or the other will fail due to "wear and tear". I've rebuilt some tensioners... just by replacing the pulley bearing. I've replaced some tensioners... because the spring broke,,, even though the pulley bearing was still in good shape.

A belt "out of line" on a tensioner or idler pulley,,, means a failed bearing or problem within either of BOTH rotating axis of either part.
 
Sorry for bringing this back, @nhtshd88 did you ever find what the issue was? Was it indeed the harmonic balancer?

I just replaced my idler pulley and tensioner, and I noticed the belt was riding in the same spot as OP on the idler pulley, on the very edge.

Started the car this morning and the belt flew off.
 
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