Jason @ Streetwerke

After asking a lot of you about how you perform your timing belt jobs, it's very clear to me that most of you are not doing it correctly. I read the AR Tech article most refer to and it leaves out a few critical steps.

Most people are NOT doing the following:

1) using properly fitting VAG cam lock bar
2) using the Bentley manual for procedure guidance
3) loosening the cam sprockets to ensure no preload and proper timing
4) not locking the crank in position with the VAG lock pin
5) applying the required pre-tension on the tensioner roller

From cars that I've seen in my shop with customer installed timing belts, we've noticed all of them are off about 1/2 to 3/4 of a belt tooth. This is really obvious when correcting the problem using the VAG tools and proper procedure.

My conclusion is most of you who have done this job on your own fall right into that demographic (timing slightly off). I suggest you redo the job correctly with the proper tools and see what you end up with.

As for the parts failing, I recommend you reuse the stock (original) bolt for the tensioner roller. Use loctite on it too. Discard the new bolt that comes with the tensioner roller. Also, Ruville is Audi OEM on the rollers, so you can't go wrong there. Febi is OK as well. Make sure you install the plastic belt covers properly too, we've seen the covers rub on the belt and make an odd noise when install wrong. This happens when the covers are placed too far inboard toward the engine, on the other side of the correct groove.

Based on the potential for a costly disaster if the timing belt job is done wrong, I would think everybody would be really careful and take the Bentley seriously (instead of just a torque reference). Anyway, I'm not here to scold or judge...just offering some constructive advice for the novice hardcore DIY types here. Yes, I know plenty of you have done this job and "it's fine". That doesn't make your timing right though.<ul><li><a href="https://forums.audiworld.com/s4/msgs/2044659.phtml">The original post is here.</a></li></ul>

JasonS4+Festicle

awesome info - thanks for that post - I'll be doing mine this summer.......

RKA

This doesn't make sense to me. If you set the crank at TDC, and the cams are off, wouldn't they be off a full tooth (or more) in either direction?

Jason @ Streetwerke

Take a look at the Bentley procedure, it will make sense. If you don't loosen the cam sprockets when doing a new belt, the timing will be off since you are tensioning the new belt to the length/position of the old belt. You need to loosen the sprockets so you naturalize the belt (no preload) while the crank and cams are locked in position at TDC. Once the belt is tensioned and all the slack is in the right area, you can tighten down the sprockets and all is perfectly timed in relation to each other. When people don't lock the crank, cams, and loosen sprockets...they end up with timing that may work but isn't perfect. Result is a loss of power and maybe a little bit of a rough idle in some cars.

Can't tell you how many people thought they had it right, but when we do it the "right" way for them later...we find out how wrong they were. Again, timing is off a full tooth at the extreme or maybe a 1/2 tooth in some cases.

jtsai

thanks for the info...doing my this week

Blue2

Thanks Jason, I'm getting ready to do one

lemieux@curbside

i found out about the sheer resistance of the tensioner bolt after i finished mine up.

lemieux@curbside

agreed 100% (and the sprockets don't have a set spot on the cams)

Jeff Vader - boscoj

nightmare

AxelS4

well, I know what you mean. I am sure that I did not want to do a timing belt job at all, I just had to put the pieces back together after my second water pump seized. I have the Bentley CD, but I do not have the CAM lock tool. Consequently, I put it back together exactly as the damned seized water pump left it - with all new parts in there. I am fairly sure that this is what might happen there - just from my own experience.