Cambelt snapped need advice

As already posted my cam belt snapped the other day (300tdi).

I got the timing case off today to find this



It's done less than 30K and is under three years old, as you can see it's got the updated kit with the guides on the crank pulley.
So how has it wandered so far and eaten the belt ?

Some more photos so you can hopefully shed some light on this





Note the groves worn by the belt.
Now I don't know how this has happened with the updated pulley.







what was left of the belt



I recently changed the injection pump (using a locking kit) but haven't done anything else in the cam belt area.

I don't want to just chuck the new belt on (full kit) and have this happen again.

check idler bearings and alignment of pulleys with a straight edge

Idler bearing has some play, tensioner has very little, both looked inline with crank pulley using a straight edge.
The cam pulley is 3 or 4mm further out than the others, is this normal ?

That dose look a bit of a mess there Mark , the belt must of been haveing abit of a wander to thin it down that much some thing is deffo out of line.

brianp38dse said:

That dose look a bit of a mess there Mark , the belt must of been haveing abit of a wander to thin it down that much some thing is deffo out of line.

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That's my worry, the belt is less than 1/2 of what it was, has stripped teeth and is snapped.

Looking the marks on the pullyes its been like that for some time.

Mark, check the tooth pulley is not free on the crank shaft.

Mark, I think that when the IP was refitted it has been installed out of line, I remember reading somewhere that early TDI's had T-belt problems because of a tendency for the "from the factory" and subsequent pump axial alignment to be incorrect in relation to the camshaft and crankshaft axis.
This misalignment throws the T-belt off track fore or aft and causes the edge of the belt to rub/fray against the front or rear of the timing case, once the belt edge starts to disintegrate its all downhill from there, (but you already know that bit).
I'd be 99% sure this IP misalignment is your problem given the history and what you've found.
To ensure no re-occurrance of the belt mash, you need to check the IP sprocket angular alignment to the other elements of the timing train.
You should be able to achieve a good result using a good suitable straight edge across faces etc.
Whatever you do don't be tempted to simply fit a new belt without thoroughly checking alignments and replacing the tensioner and idler rollers, consider also, from recent experience of a mate of mine, replacing the studs and bolts that hold the tensioner and idler, his idler stud broke and caused the timing to slip trashing rockers, pushrods and a belt with about 10K on it, otherwise 30K or less from now you may be in the same place.

misalignment was caused by people tightening pump rear support bracket incorrectly, fastenings were changed to allow for it as a fix, some insisted on tightening bracket to pump then pulling bracket upto engine by the bolts

Yes James, that was the general idea of what I read a while back, but I also thought some of the early TDI's left the factory with some problem that allowed movement and early failure of the T-belts, there is an upgraded or extra bracket available?
I own 2 TDI's and although I have replaced T-belts have never experienced any uneven edge wear or such.
My '97 flogged out the crank keyway and crank sprocket after 300K, fixed with a 4" grinder and 1mm cutting disc, it now has a long feather keyway 5mm wide.

Gazbo said:

Yes James, that was the general idea of what I read a while back, but I also thought some of the early TDI's left the factory with some problem that allowed movement and early failure of the T-belts, there is an upgraded or extra bracket available?
I own 2 TDI's and although I have replaced T-belts have never experienced any uneven edge wear or such.
My '97 flogged out the crank keyway and crank sprocket after 300K, fixed with a 4" grinder and 1mm cutting disc, it now has a long feather keyway 5mm wide.

Click to expand...

yes bracket was altered to help

Thanks for the pointer guys, gives me something to look at.

I'm wondering if there was a bit of crud under the IP when I fitted it, but the rust on the pulley looks to have been there longer than that, so the belt was possably on the move before then.

Thought I'd better update this thread.

It's now running and covered around 500 miles.

Looking at the back of the tesioner mount it shows signs of not being seated properly, I think this is what was pushing the belt out of true.