So... odd one here. I'm new to Audis, but not new to working on my own cars... anyway... 1999 2.8L 30V A6Q...Changed the timing belt, tensioner, rollers, t-stat, the whole enchilada. Put it all back together and the motor fired right up, but developed a "scrubbing" noise under the timing covers. Tear it back down and discover the timing belt is "walking" forward on the cam pulleys. Everything is seated and looks as true as I can tell with my eye. Questions:

a) Ever seen this before?

b) Is there any reason, on this particular motor, why I couldn't turn the motor over with the starter (very briefly - no ignition) while torn down to the t-belt to watch how the belt travels? I can't reproduce the problem turning the crank by hand. (I understand the danger if the belt comes off)

I'm down to replacing the orignal components one by one until I find the offending roller/part...

Other thoughts?

Thanks!
JJJ

 

Ive seen that before and it was a pulley offset, did you undo any pulleys or use them to turn the engine?? especially the cams

 

If you remplaced the idler roller make sure there is a washer behind it.

 

Thanks for the response guys...

1) Did not remove or mess with cam pulleys.

2) I do not remember a washer behind the idler roller, either on the one I removed or on the new one... will double check tomorrow as I kept all of the old parts. Assuming that would push the roller further forward, that would presumably worsen my issue of the belt walking forward though.

I'm going to be working on it again tomorrow so I'll let you know how it shakes out. A local mechanic also mentioned that he had once received a new belt that "walked" and it turned out to be a manufacturing defect in the belt... who knows... Thanks again for the info.

JJJ

 

I was thinking that if that pully was in to far that would cause the belt to be angled towards the front of the car at the top causing it to want to walk foreward. There is definatly a washer behind that roller. The new one should have come with one as well.

 

Ahhh... see your poiint. Headed downstairs to dig into it. Would love for it to be that simple. :-) thanks.

JJJ

 

Well... turned out to be the water pump pulley. 2mm further forward than the rest of the belt path. Put old pump back on... all is well. Now just have to wait for new pump to arrive.

Thanks for the thoughts and, BTW... the washer was under the roller. I just didn't remember it.

JJJ

 

It always is.

Thats really strange. Never seen that before. Its almost always that washer behind the pully missing. Was it the wrong pump, or was it defective?

 

also, on my 2.7T, the belt was removed in the past by the dealer then the covers were not aligned properly and hit a roller.

 

Water pump was simply defective. It appeared identical in every other respect. The pulley was simply not in the right place on the shaft. Old pump is back in for now and car/belt is running fine. I'll throw a new pump on in a week or so...

JJJ