Passat Timing Belt Tensioner

Recently I had the timing belt and water pump replaced on my '03 Passat V6 Station Wagon with 4motion because the plastic impeller on the water pump broke. Mileage is around 90 K.

Approximately 10 days later the the bolt that holds the timing belt tensioner broke and created quite a calamity in the engine. Still waiting to determine if the patient will survive or not.

My question is this. When the timing belt is replaced is it necessary for the mechanic to have any interaction with the timing belt tensioner, i.e. tighten, loosen, or adjust in any way?

My mechanic tells me it would not have been necessary to go anywhere near the tensioner.

My second question is what would cause the bolt to break? Should I be suspicious that it was over-torked or chalk it up to wear and tear on a 9 year old car with 90 K miles???


“My mechanic tells me it would not have been necessary to go anywhere near the tensioner.”

Did your mechanic really say that? Unless there is more to the story this is flatly dishonest. One cannot remove or reinstall a timing belt without dealing with the tensioner. Its possible s/he is saying that there was no need to deal with the tensioner bolt. But that isn’t true either. I suppose it may be different on some cars but the bolt is loosened and retightened during installation. You probably should have gotten a new tensioner anyway.

I feel like there’s something here I don’t know about all that went on. But the most likely case is that the bolt was overtorqued and that is why it broke. A defective bolt is possible, I suppose. But in general the tensioner bolt doesn’t “wear out.”

LOL…if your mechanic didn’t go anywhere near the tensioner, then he didn’t do the timing belt job right in the first place. The tensioner has to be adjusted after the new belt is installed.

I may have para-phrased the mechanics comments but that was pretty much the essence of what he said. When I asked if they would have to adjust the tension on the new belt via the tensioner he told me that the new belt goes in and that’s pretty much it There is no adjustment. I will revisit that conversation with him to be sure. He did seem relieved that the problem was caused by the tensioner giving way and not the timing belt itself. For what it’s worth I did see the pulley and remaining bit of bolt and it seemed to look fine.
Also, I don’t think I left anything out from my description of the issue. The water pump’s failure (no heat) is what prompted the timing belt work in the first place.
If a bolt was defective would it take this 8 years to reveal itself??
Not being a mechanic I guess I don’t know what I don’t know which is the reason for the posting. I am not very mechanically inclined and I am trying to understand at least a little bit of this. It may not be of much help in this instance but it may indicate a bigger problem, like I need a new repair shop.

VW 1.8T engines in your vintage car are known to have catastrophic failures of tensioner even at 70k miles.

I just glanced through the procedure listed by Autozone’s online repair manuals. It lists no need to loosen the tensioner bolt before rotating it out of the way.

The statement “it would not have been necessary to go anywhere near the tensioner” is completely wrong. However, it may be that it wasn’t necessary to do anything with the tensioner bolt may be accurate.

However, something about this is just not right. Coincidences do occur, but this is just a little too weird. (Andrew_j’s comment below doesn’t apply if that problem is limited to the 1.8 engines. If yours is the 6 cylinder then it should be the 2.8). Just b/c the tensioner bolt doesn’t need to be tightened this doesn’t mean that it wasn’t.

In any case, IMHO the tensioner should have been replaced. This is not always done and isn’t required, but is a best practice for exactly this kind of reason.

This is the 6 cylinder 4motion engine.
Another mechanic I consulted agrees that the tensioner should have been replaced, but since I believe that is not recommended by VW it may be of little consequence.