AHU - Air in Fuel System

I didn’t notice the orientation, but if the nut isn’t loose, how would it move? Even if the tensioner is defective, the nut locks the position. I’ll need to look at the new tensioner I have... I never really questioned how they work.

Perhaps the nut was loose and allowed the OP’s slippage?

-Todd

What would result it different orientation of the center with the same parts other than winding it in different directions?

Indicators not quite lined up in the first pic? Not enough off to account for the hub position.

Different belt path? Not likely.

Belt not seated in a sprocket? Would've settled in when motor was rotated and showed up as something out time and the indicators would be way out of alignment.

Belt stretch? They don't stretch that much.

Also note in the pichers that the tensioner appears lower and to the left against the background. Doesn't look like parallax can account for it since the camera positions seem pretty close.

Thinking about it, the center is eccentric and belt tension is taken up as it rotates. The only difference between this style and the earlier style is the addition of the spring loaded tension gauge. If wound in the opposite direction, the gauge would likely not register properly.

If wound in the opposite direction upon installation, this could be why the belt was loose and the indicator was close, but not accurate.

-Todd

The way I had it explained it that it can loosen up the nut when it's the wrong direction. Even you think about it, it's pulling the nut to loose, instead of the other direction well be pulling it to tight. I always make sure that it'll be tightening the nut I'd it works loose.

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I wish I had paid closer attention when I loosened the tensioner to advance the IP pulley - I can't say with certainty how loose or tight it was. Certainly not loose enough to be finger tight, but it didn't require much effort to loosen it either. I wouldn't expect to use a lot of force to loosen it though, given that the spec for that nut is only 15 ft-lb.

If it's unlikely that I have a bad tensioner, then my best guess is that the nut came loose enough for the tensioner to move. Did I fail to tighten it adequately when i first installed the belt? Perhaps, but if it only takes 15 ft-lb then I'd say it's more likely that I overtightened it. I know that I didn't put any loc-tite on the threads - is that standard practice?

As far as winding it the wrong way at installation, I guess it's possible, but I highly doubt it. Unfortunately I have no way to confirm one way or the other, but surely if I'd wound it the wrong way I wouldn't have been able to drive 16K miles without incident? I'll have to play around with it when I go to replace the belt and see how i can make it look like it does in that picture.

I’ve seen cars go 50k with it being tensioned the wrong way, and I’ve heard of them grenading within 1k. It’s a crap shoot.

I’ve never used Loctite on the bolt and the Bentley doesn’t call for it.

This is a properly tensioned tensioner:




And this was tensioned backwards, note how new it was:

Wow - doesn't look like the story associated with exhibit B had a happy ending.

Stay tuned for updates - replacement parts are on the way and I'll take it apart and post my findings when I get home next week.

Just for fun, before taking everything apart, wind the tensioner backwards and see how it looks.

Will do. I plan to try both winding it backwards and loosening the tensioner to see how I can make it look like the picture in question. If anyone has other scenarios they'd like to see tested, let me know and I'll be happy to give it a try.

After getting stuck in the Midwest for a couple extra days thanks to bad weather, I finally made it back last night and got straight to work. The results appear to be reasonably conclusive.

For reference, here's the picture I took prior to retensioning after advancing the IP sprocket:


And here's the tensioner correctly tensioned after advancing the IP sprocket:


Here's a picture I took last night after loosening the tensioner from it's correctly tensioned orientation:


Last but not least, here's the tensioner loosened after being incorrectly tensioned (CCW):


Try as I might, the only way I could get the tensioner to look like it did in the first picture was to wind it the wrong way, and then let it slip back a bit (and believe me, pride compelled me to try to find any other explanation).

In the end, it appears that I have to swallow said pride, and accept that I must have tightened it CCW. That would explain why it loosened (I'll refrain from using the term failed, since the failure wasn't the tensioner) and the IP skipped a tooth. I'm feeling incredibly lucky that the end result was a few days of frustration, and not a ruined engine.

Now for yet another question. Should there be any washers associated with this new style tensioner? I discovered there are 2 tensioner washers sold by IDParts - a spring washer and a flat washer. I ordered one of each to be safe, but neither washer was installed with the tensioner when I took it apart. I doubt that I would have missed reinstalling washers when I did the job last time...but I also doubted that I would have wound the tensioner the wrong way.

The Bentley doesn't have details for this type of tensioner, but I called IDParts and was told the spring washer should go behind the tensioner and the flat washer should go between the tensioner and the nut. Can anyone confirm that's correct?

And as long as I'm asking questions, does anyone recognize this washer? I haven't got a clue when I dropped it, or where from, but I found it when I was taking things apart. It doesn't look like either of the washers I just ordered.

kurtzl said:

Now for yet another question. Should there be any washers associated with this new style tensioner? I discovered there are 2 tensioner washers sold by IDParts - a spring washer and a flat washer. I ordered one of each to be safe, but neither washer was installed with the tensioner when I took it apart. I doubt that I would have missed reinstalling washers when I did the job last time...but I also doubted that I would have wound the tensioner the wrong way.
The Bentley doesn't have details for this type of tensioner, but I called IDParts and was told the spring washer should go behind the tensioner and the flat washer should go between the tensioner and the nut. Can anyone confirm that's correct?

Click to expand...

This is going from what I know personally and not from any service bulletin or white paper etc.

There was never a washer used on the backside of the tensioner, I don't think there was ever one used on the ME, MF, 1Y, 1V, AAZ either and I would not install one. I've never seen one EVER.

As for the front there were a couple different situations, one used a nut with a spring washer, which was later superseded by a self-locking nut which has a shoulder on it, and is the one most often encountered on engines in the field.

If your existing setup has the shouldered nut, and it looks like it does, I would continue to use that without changing. You could replace it with a new one but I don't really think it's necessary. I've never replaced one with new and it seems to me that if VW classified it as one time use that the tensioner makers would include a new one with the new tensioner.

And as long as I'm asking questions, does anyone recognize this washer? I haven't got a clue when I dropped it, or where from, but I found it when I was taking things apart. It doesn't look like either of the washers I just ordered.

Click to expand...

That doesn't look like anything I'm familiar with, where in the car did you find it?

Steve

I agree on no washer under the tensioner.

Look at the second picher in Post 96 above.

What on the back of the tensioner is going to fully seat on a washer??? The stud hole is eccentric to the larger "tubular" part that seats against the head. Looks like a small washer would cause the tensioner to tilt.

Thanks for the confirmation. I didn't remember any washers, and it didn't seem like any would belong there, but I'm second guessing myself on everything now . I do have the shouldered nut, so i'll just install the new tensioner with no washer either behind or in front.

Steve Addy said:

That doesn't look like anything I'm familiar with, where in the car did you find it?

Click to expand...

It was sitting back behind the timing belt, up against the block and down towards the crank sprocket (yet another thing that could have ended very badly). It looks like the sort of thing that might get inserted in a plastic part to keep it from wearing, but I can't think where it came from.

If it’s small (sorry, no frame of reference) then it’s probably one of the guards for the lower timing belt cover. It has 3 of these, two for bolts (long and short) and one for a nut up by the T-bolt that is under the injection pump. I’ve seen them pop out from the lower timing belt cover being cracked due to over-tightening, vibrations due to being loose, and just heat cycles.

Abacus said:

If it’s small (sorry, no frame of reference) then it’s probably one of the guards for the lower timing belt cover. It has 3 of these, two for bolts (long and short) and one for a nut up by the T-bolt that is under the injection pump. I’ve seen them pop out from the lower timing belt cover being cracked due to over-tightening, vibrations due to being loose, and just heat cycles.

Click to expand...

Sorry - should have thought to include scale. Here's a better picture:


It's definitely too large to be one of the guards for the bolts that hold the lower cover in place, but it looks like you were on the right track. It appears likely that it surrounds the head of the water pump bolt that's directly above the nut that goes on the T-bolt for the lower cover. The lip on it then sits flush with the level of the T-bolt hole on the inside of the cover (you can see in the first image how the plastic is slightly raised where the bolt comes through).


I may try to secure it to the lower cover with some hot glue but I'll more likely just remove it entirely.

2,000 miles later all is well. Starts up immediately like it used to, and no more diesel leak at the injection pump. I even calculated 50.8 mpg at my last fill, so it seems to be running as well as it ever did!

I also managed to replace the missing T-bolt for the lower cover (I saw evidence this time that the serpentine belt had rubbed on the cover). Turns out it's a 2 minute job, and doesn't require removing the WP. I'll post a how-to in the next couple days for anyone else who wants to put that bolt back.

Thanks again to everyone who helped with troubleshooting, and thanks to Abacus for spotting that the tensioner was wound incorrectly - that's an impressive eye for detail!! I'd like to believe I wouldn't have made the mistake a 2nd time, but now that I know I've been guilty before, I'm definitely hyper-aware of it now.

Glad I could be of help. I hope all stays well.

I have had to replace a few of those T-bolts and did so by using some shrink tubing to connect a wire to the t-bolt and gently pulling it through. I am interested in how you did it in case there is a better way.

Thanks for posting this all the way through to the solution. It was a great example of diagnosing an issue and getting a positive outcome. It also embedded the importance of timing for these engines!


JP

With all the help I received, posting the entire process was the least I could do

Hopefully the troubleshooting procedure will prove useful to others, and save someone else the hours of frustration I went through!

Between my coworker quitting and my family coming out to visit for 3 weeks, it seems my good intention of posting a how-to for the T-bolt in a "couple days" was laughably optimistic

Anyway I finally got around to it - let me know if anything is unclear or incorrect.

http://forums.tdiclub.com/showthread.php?t=500711