Broken Tensioner - How could this happen?

[diesel4ever]

The car ran fine but there MIL came on saying the injection start was out of range. Checked the TB and it felt loose. At first I thought the tensioner came loose, but when I tried the nut it was tight and in the 'tensioned' position.
So I thought the belt stretched, although I never heard of something like that. So, I proceeded to change the belt. Once I removed the tensioner this is what I found.

The rear spring tab (not the one that hooks in the rear plastic cover) was cracked and dislodged. Did anyone experience this and what would cause it.
I did complete TB 2.5 years ago and 37,400km driven since

 

[jettawreck]

Looks very similar to the one that came out of the '03 that I bought with a "broken TB". TB was intact, but the tensioner had failed similar to that one. Don't know why, except that it had 167K miles on it when it broke for the prior owner(s). (They weren't much into maintainance, I guess).

 

[Lug_Nut]

I've seen two others like this. One completely sheared off the retaining tang and the belt lost tension, the other started to tear, but didn't completely shear.

 

[diesel4ever]

Thanks for feedback gentlemen. So, it appears it's rare, but it happens.
I wonder if you would remember what brand were those that you found they failed. Mine was made by Litton.

 

[Ski in NC]

I wonder if this happens when some strange set of circumstances causes the engine to spin backwards. That would put tensioner on tight side of belt and maybe (??) overstress the spring tang (??)

Or debris caught in belt, causing tensioner to over extend.

 

[diesel4ever]

I wonder if this happens when some strange set of circumstances causes the engine to spin backwards. That would put tensioner on tight side of belt and maybe (??) overstress the spring tang (??)

Or debris caught in belt, causing tensioner to over extend.

TB area was clean and no sign of damage on timing belt.

 

[IndigoBlueWagon]

It's Litens, not Litton. They make the OE tensioners for VW. And I'm not sure this is what caused this failure, but I have been told that if if it's not adequately tensioned on install the tensioner tang can hammer against the tensioner and eventually break.

 

[jettawreck]

It's Litens, not Litton. They make the OE tensioners for VW. And I'm not sure this is what caused this failure, but I have been told that if if it's not adequately tensioned on install the tensioner tang can hammer against the tensioner and eventually break.

Yes, Litens is the OEM supplier and the top source of the tensioner with almost everyone (except maybe Prothe).

The theory above makes sense and in the pic it looks like the tang had been hammering around. I wonder how the slot looks?

 

[paramedick]

they can also break if tensioned counter-clickwise

 

[Abacus]

Send it back to Litens for analysis, they'll be able to tell you what happened.

 

[Losha]

This only happens at couple reasons, 1) is over/under tensioned, 2) incorrectly set like counter clockwise tensioned, 3) very rare due to very high mileage or defective part (which I haven't seen to happen yet). Most likely tensioner was tensioned incorrectly or back tab was not in place correctly.

 

[djnelsontdi]

I did the TB on my 03 Jetta last summer, first time it was changed and was surprised to find my tensioner was in the same condition. It was the factory installed. Not surprising to me if you work in manufacturing now days. Quality takes a back seat to production. Get it out the door and we'll worry about it if it fails under warranty.

 

[Losha]

I have seen within past 6 months 3 TDI ALH that came in to my shop (drove in) with tensioners incorrectly set when belt was replaced within a year time frame and all 3 of those nearly had tb failure. One NB had loose TB of about 1"+ play from top roller, prior me had TB job done 40K miles ago. Second one NB had messed up tensioner as well, when I was checking timing marks and while spinning engine by hand I had belt slip on crank by 3 teeth. Then 3rd TDI jetta had TB & water pump replaced 9 months prior to me as well had tensioner that wasn't set correctly and tab slipped off from hole and almost destroyed TB. Then a month ago another Jetta TDI came in with broken TB that had complete TB job done 5k miles ago, and story was same thing tensioner was set incorrectly. Without seen how your tensioner was set prior you removed it we can't confirm if it was installed correctly, but based on my experience and others these tensioners usually fail only when installed incorrectly and very rarely from being defective.

 

[Abacus]

I just did a timing belt with a factory Litens tensioner dated 50/95 with 137K on it, and it looked fine.

I have done timing belts on cars that other people 'just had changed' and found them in the same
condition...broken from being tensioned backwards.

I have also e-mailed Litens to ask about re-tensioning their tensioners once installed
(the answer is yes, it's OK), and the impression I got from their e-mail was one of pride
and quality of work. I'm sure they would be happy to get a failed tensioner for analysis.
I have the engineer's contact info if you or the OP wants it.

 

[Lug_Nut]

This only happens at couple reasons, 1) is over/under tensioned, 2) incorrectly set like counter clockwise tensioned, 3) very rare due to very high mileage or defective part (which I haven't seen to happen yet). Most likely tensioner was tensioned incorrectly or back tab was not in place correctly.

One of the two that I have seen in a failed state was one that I personally had installed a few thousand miles earlier. It was not over or undertensioned, it was not reverse tensioned, at a few thousand miles it was not very high mileage, and at installation there was nothing to indicate that it was defective in any way.

some added notes: The stud in the block on which the tensioner is rotated had come loose from the block on this example. The belt tension could have been lost when the stud loosened. How the stud loosened I don't know, but I now remove and thread-lock the stud into the block on the timing belt changes I do. I'm also a bit more thorough in examining the tensioner before installing it. I no longer just take it out of the box and put it on.