How can a pulley come off, but the serpentine belt is still tight?

[looking4firewood]

Strange as hell, and maybe I just don't know what I don't know. Got into my 2008 Ranger, 4L, 4x4, automatic, started it up, got a whirring sound. I figured no check engine light came on, the temp did not go up, power steering was fine, AC was working, drove about .5 miles and there was a BOOM, the whirring sound went away, but there was an odd clacking sound. When I got home, lifted the hood, and saw a pulley sitting below the fan. Without that pulley, how could the serpentine belt still be tight? Is there only 1 belt on my Ranger, or is it possible that there are 2? What could this pulley have come off of and still have everything working?

 

[alwaysFlOoReD]

Pic?

 

[JoshT]

I can think of two possibilities, but can't say for certain without seeing what happened.

1) Idler pulley between the PS pump and Alternator broke off, but the tensioner had enough motion to take up the slack.

2) The tensioner pulley itself came apart, but there is still enough there for it to ride on and keep tension on the belt.

Not sure about the plausibility of the first, though if it broke the pulley would have likely bounced off of your hood causing the boom. Clacking sound could have been the pulley hitting the fan, or fan hitting the shroud from other damages.

I doubt the second, if that pulley had come loose from the bearing it still would have pulled the gelt off the tesnioner. Also due to the positioning, I don't think it would have ended up where you found the pulley at.

You should only have one serpentine belt on an '08 4.0L.

EDIT: though of a third. The pulley separated from the harmonic balancer. I don't really see that happening, and everything else continuing to work, as that is the primary (only) driving force of the serpentine belt. The belty would have been slipping like crazy and burnt up in short order if it managed to stay on the balancer.

@alwaysFlOoReD is right, pics would help a lot in diagnosis.

 

[alwaysFlOoReD]

I lost the tension pulley on a dodge 5.7l. The belt still worked sorta if you didn't put a load on it but was obviously loose. I think Josh has the closest answer so far.

 

[looking4firewood]

Some pictures, and it is grooved for the serpentine belt

 

[looking4firewood]

I can think of two possibilities, but can't say for certain without seeing what happened.

1) Idler pulley between the PS pump and Alternator broke off, but the tensioner had enough motion to take up the slack.

2) The tensioner pulley itself came apart, but there is still enough there for it to ride on and keep tension on the belt.

Not sure about the plausibility of the first, though if it broke the pulley would have likely bounced off of your hood causing the boom. Clacking sound could have been the pulley hitting the fan, or fan hitting the shroud from other damages.

I doubt the second, if that pulley had come loose from the bearing it still would have pulled the gelt off the tesnioner. Also due to the positioning, I don't think it would have ended up where you found the pulley at.

You should only have one serpentine belt on an '08 4.0L.

EDIT: though of a third. The pulley separated from the harmonic balancer. I don't really see that happening, and everything else continuing to work, as that is the primary (only) driving force of the serpentine belt. The belty would have been slipping like crazy and burnt up in short order if it managed to stay on the balancer.

@alwaysFlOoReD is right, pics would help a lot in diagnosis.

Josh, small world, my wife grew up in Ft Valley. We still have a house there.

 

[looking4firewood]

Some pictures, and it is grooved for the serpentine belt

It looks like it is the outside part of a pulley assembly

 

[JoshT]

Yep, your crank pulley/harmonic balancer came apart. It happens with age and miles. Get a new balancer, a new belt and put it back together. Check your fan over good to make sure it didn't get damaged from the pulley bouncing around in there.

I'm surprised that the pulley came off and the belt stayed on, but it obviously did. It's still tight because the diameter didn't change that much, the tensioner had enough range to keep it tight.

 

[Curious Hound]

That's a weird one. I never would have expected that.

 

[looking4firewood]

Yep, your crank pulley/harmonic balancer came apart. It happens with age and miles. Get a new balancer, a new belt and put it back together. Check your fan over good to make sure it didn't get damaged from the pulley bouncing around in there.

I'm surprised that the pulley came off and the belt stayed on, but it obviously did. It's still tight because the diameter didn't change that much, the tensioner had enough range to keep it tight.

$200 in parts and it is whole again. Thanks for the input.

 

[MaicoDoug]

I need to look at mine. Thx for the thread!