Eating timing belts

[Ibuprofen]

I have had one timing belt partially fail once already, though the belt didn't fully separate it did prevent the engine from starting. After retiming with a new belt and tensioner it fired up without issue. I've been keeping an eye on the new belt and it appears that it is also destined for the same fate. Attached is a photo of the current belt at the IP sprocket with around 1500 miles on it. This is a 50 degree mTDI in a Vanagon.



I will pull the aux belt and covers and get a closer look at things but I wanted to get any opinions of folks that may have seen this before as I've not been able to find any obvious reason why the belt is trying to depart. My van has quite the arse sag and the engine tilts that way somewhat, but there are a lot of saggy Vanagons out there.


Any thoughts on why the belt wants to head away from the engine? Thanks

[ORCoaster]

Wow, way too much wear for 1500 miles unless it is on way too tight or rubbing on something.  I have seen less wear on some with ten times that mileage on them. Something is not right in Denmark.

Pulley alignment is generally the culprit for belts walking away from the intended direction.  Check the IP bracket bolts to see if they are good and tight under the IP.  Or just see if you can get the bracket to wiggle some with a long screwdriver between the engine block and the bracket.  I know it is a pain to get under and work on it but that might keep you from having to pull the IP just to see they bolts are indeed tight as need be.

[libbydiesel]

That looks terrible.  How tight is the belt?  You can clearly see the tooth impressions in the belt which makes me think it is waaayyy too tight. 

[Ibuprofen]

What makes this even more confusing for me is that I swapped the injection pump, ip sprocket, ip mounting bracket, and new tensioner when this new belt went on in replacement of the shredding belt. When I look at the belt with the engine running, the alignment seems fine to me.

The tensioner tightness is simply lining up the nub with the slot, yeah?
There isn't anything behind the tensioner aside from the metal tin? Tensioner -> Tin -> Engine

I will give it another hard look and probably take a video. The TDI has nice torque over the stock engine but leaving the belt behind is pretty extreme.

[smutts]

You will likely get a "whirring" sound with an over tight cambelt. They won't last long overtight, nor will the bush bearing in the injection pump. The teeth of the belt look to be shredding too, also likely to be overtight.

There are some crap tensioners out there, usually in a "GENUINE!" Gates, Dayco, or whatever timing kit box, slathered in Sellotape, filled with assorted no name ***e, bought on Fleabay. (Library image of course )

I've been screwed twice this way.

[Ibuprofen]

Hrmf, bummer that there are bad tensioners out there. I got mine from IDParts. At ~$50 I'm not thrilled to swap it out again but beats a ruined engine.

Here's a short slow motion of the belts, it looks like it starts to move on the intermediate pulley. Cam and IP pulleys look okay to me.

https://www.youtube.com/watch?v=vwyr3ra-aAw (ignore the busted exhaust mount...)

cam: https://www.youtube.com/watch?v=nFMLdCpYs1g
IP: https://www.youtube.com/watch?v=WV__fjJ9K5I

[libbydiesel]

Is the initial picture in this thread where the belt normally runs on the injection pump?

[Ibuprofen]

Yup. There is a short video of the IP in my last post as well if you didn't see it.

[libbydiesel]

I missed the cam and injection pump videos.  I have never seen a belt get worn on the side like that unless it was walking off the injection pump.  What is the dust that is on the backing plate by the injection pump sprocket?  The tracking all looks fine.  Any chance one of the outer covers  or any other part is touching the timing belt when those parts are installed?   

[ORCoaster]

I watched the vids and I think I would be checking the belt tensioner bolt.  As the belt comes up from the crank it appears to rub on the tensioner and that is what we see as wear on the front of the IP.  I also hate to say it but you might need to check the crank pulley as well. 

A little wobble might be doing the belt in. 

First check the bolt in the block on the tensioner.  It may just be a tad loose. 

[libbydiesel]

Have you removed the crank pulley and the lower cover and looked for any potential causes there?

[Ibuprofen]

Libby, the dust is belt material and I don't see anything obviously rubbing except for the tensioner.

I'll take a closer look at the tensioner bolt and lower pulleys. Here are a couple of pictures above the IP, I'm wondering if the sprocket I used sits too far from the IP bracket? It was cheaper for me to get a brand new sprocket than it was to find an ALH sprocket and get it machined, but I'm wondering if maybe I need a different sprocket. If someone with that setup, a machined ALH sprocket and land rover pump, doesn't mind eyeballing theirs for the bracket offset next time it's convenient I would very much appreciate it.

My engine:






Image I found via google of someone else's ALH sprocket setup:




Thanks!

[libbydiesel]

That does look like an excessive gap between the injection pump sprocket and the pump bracket.  I hadn't noticed the offset before.  If that sprocket is out overly far, then the belt tracking as it does would be too far out and the mystery is solved.  What injection pump sprocket/hub setup are you using? 

Here is a very easy way to determine if the tracking is OK.  Remove the lower crank pulley and lower timing cover, leaving the crank sprocket and timing belt in place.  Rotate the crankshaft through a dozen revolutions or so by hand while looking at the belt tracking on the crank sprocket.  If it wanders to the outer edge or beyond the outer edge of the crank sprocket, the belt is tracking too far out and you will need to make adjustments. 

[Ibuprofen]

I would love to know how many mm/inches it is from somewhere on the pump (interface with pump mount) to the edge of the ALH sprocket, then I can know if I'm way out or not.

The sprocket I'm using is 028130111F https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/pulley/028130111f/, the hub is the stock one from the land rover pump.

[libbydiesel]

Hmmm, stock LR hub spaces the sprocket out farther than the VW ALH hub.  I believe that sprocket you have is the late AAZ sprocket and I would be amazed to find out that fitted to the LR hub arrived at the correct offset.  I have not used that sprocket, though, so I can't really say.  The distance from inner edge of the sprocket to face of injection pump (not bracket) is 13-14mm.  If the inner edge of the sprocket is farther than 14mm from the mounting edge of the injection pump then you have found your issue.