belt tensioner question?

K, my belt tensioner fell off of my 93 3.1. My belt is fine, not torn up, but the belt tensioner was kind of sitting weird and I was able to pull the unit off by hand. The mounting bolt was still in place though, and nothing on the tensioner seemed to be broken. So, i'm wondering what has happened? I've included a picture of my tensioner and if anyone has any theories or sees anything out of place on here, please let me know.
Thanx

http://pic20.picturetrail.com/VOL81/1990679/3849838/302424195.jpg

It seems as if there should be a big washer or set of washers between the bolt head and the tensioner assembly???

You've got all kinds of buggered up metal on that thing...does the pulley turn? If so, does it turn with a slight damped feel, or dry and gravelly or hiss when spun?

Either the pulley bearing failed, or is failing, making the tensioner jitter back and forth against the spring until the casting failed from fatigue...

Occaisionally you'll see one go like that when a water pump or other belt driven accesory suddenly locks solid...puts so much sudden load on the belt, the tensioner tries to absorb it all and gets snapped off..

again make sure all pulleys rotate freely because this is either a worn idler from age or something is binding. a/c compessor pulley bearing is common on these............

The pulley spins absolutely fine, very smooth and easy. It's not a question of it binding up, it's a matter of this whole unit falling off for whatever reason. As I said, it seems as if there's something missing where it bolts on.

So, looking at the picture and looking at the bolt, Your saying that whole center piece/bearing slides right off? The bearing comes out of the casting

again make sure all pulleys rotate freely because this is either a worn idler from age or something is binding. a/c compessor pulley bearing is common on these............


after checking the above comments, you then replace your belt idle arm assembly as it is n/g........i hope you don't think that this can be fixed. some cash will be required to buy a new one.......

I solved the problem (new one). What happened was there was a central hub that the outer arm rotated on and it evidently sheared right off, allowing the arm and pulley to come free from the main hub that is bolted to the block. The pulley/arm assembly is held in place by a plate which also went missing when this piece sheared off. I thought that by replacing the plate I could bolt it back on, but it didn't work. Until I bought a new one could I get a proper idea of how this assembly works. Thanx for all your input though, greatly appreciated.
To clarify things further, none of my pulleys were binding either, it was just a matter of this belt tensioner under too much vibration I guess.

I solved the problem (new one). What happened was there was a central hub that the outer arm rotated on and it evidently sheared right off, allowing the arm and pulley to come free from the main hub that is bolted to the block. The pulley/arm assembly is held in place by a plate which also went missing when this piece sheared off. I thought that by replacing the plate I could bolt it back on, but it didn't work. Until I bought a new one could I get a proper idea of how this assembly works. Thanx for all your input though, greatly appreciated.
To clarify things further, none of my pulleys were binding either, it was just a matter of this belt tensioner under too much vibration I guess.

as mentioned earlier this CAN occur if a pulley bearing is binding/draging. this part should not be in motion at any time that is why it was said that pulley problems were suspect.......the only time this broken area moves is when you put belt on . i hope this is how it is now........

Yeah, I fully understand how that can happen. The tensioner doesn't move whatsoever now. I was just clarifying that in my case, it wasn't a problem with anything else in the belt's cycle at all. Every single pulley spins freely in the whole cycle. It's a mystery as to why this tensioner broke in the first place. I guess it was just age? Who knows.