I have 84k miles on my '99 A6, I don't know a lot about cars (except that I love my A6) but I'm guessing it's time to get the belt checked/replaced. Is there any way I can tell whether or not it's beginning to wear? At what mileage is the timing belt usually replaced? And I can only imagine this is going to be a fairly costly replacement? Any info/insight would be greatly appreciated. Thanks.

Audi would tell you 105k, some people will tell you 60k, I did mine at 90k. Im now at 116k and unfortunately when it was done I assume those I entrusted to do it used the OEM water pump which has a plastic pump impeller that is now slipping on the shaft, which does not flow coolant effectively through the system, so when you do it make sure you get the upgraded water pump, and get all other prone to fail parts replaced. So I guess my recommendation is to replace it at 90, and to answer your question on checking for wear, its not possible, Even when the belt is exposed, it will just look like a belt, unless of course it is frayed or cracked, but that usually doesnt happen to timing belts.

There's no real way to tell by inspection whether the belt needs to be replaced without doing most of the work that replacement would take anyway. Given the age of your car, you have age working against you as much as mileage, so I would do it soon.

If you have the work done, prices range from $800 to $2000, with most of the variability being due to labor costs. If you do it yourself, the parts cost is about $300-$500. Allocate a weekend for the work first time, a day the second time. There may be owners in your area who would be willing to advise/help.

No real way to judge wear, imo. I replaced mine at 55k, but I also drive 30-40k a year. Replacement depends on what else you do while you are in there, but I've heard estimates anywhere from $600 - $1k.
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I cannot imagine replacing the belt myself! (I'm impressed to hear that others have ventured to do so.) I was assuming that due to the sophistication of this vehicle that I should take it to the dealership - as opposed to a neighborhood mechanic. Would you all agree?

it's more tedious than difficult. The reason it's so expensive to have the job done professionally is there's a lot of labor involved, but it's all pretty simple labor. You have to take off the entire front end of the car to get access to the timing belt. The actual belt replacement takes less than an hour, depending on skills, experience, & tools. The rest of the job takes it to the 6-12 hour range. It took me longer than that. :-(

Of course, having it done professionally puts the responsibility for screwups on someone other than yourself. I'm keeping my fingers crossed that I didn't forget anything important...

To answer your question, I'd get quotes from the dealer and from an independent mechanic that specializes in Audis. Most decent mechanics should have experience with generic timing belt changes, but previous experience on a 2.7T would be a big help. I would have no hesitation in taking it to an independent mechanic with a good reputation.

where do you have your work done, its 12+ hours of labor, which means about $1k in labor, not to mention parts. if you have someone who can do it cheaper, please forward me the info, im very interested.

Yeah, i've got someone who can do it cheaper. However, I'm located in Tennessee, so unless you're from KY, AL, AR, GA, MS, NC, or SC, it's probably better for you to shop around some more.<ul><li><a href="http://www.germanperformanceoptions.net/">these guys are great (in Nashville)</a></li></ul>

between replacing Water pump, TB, Tensioner, Damper, and Idler. But that doesnt change what is charged, the labor guide says 12.1 hours to get to the Water Pump. My local Audi Dealer charges 14 hours, but thats in SoCal, so Im sure they hike up the price. How much does your mechanic charge? As far as time?

This included getting stuck twice -- once trying to figure out how to remove the viscous fan without the "chopstick" tool, and again trying to locate the hole for the crankshaft lock pin. I'll go a lot faster if I do it again.

Some of the guys on the B5 S4 forum claim to be able to do it in 6 hours now that they've done it several times. Presumably, that involves a tag-team effort, so the labor hours are still around 12.

1. Call www.blauparts.com they have all yours parts and TOOL RENTAL.
2. Get the factory manual
3. Allow yourself two days.
4. Bag and label all parts.
5. The crankshaft plug is tough to get to,
I had to disconnect driverside intercooler pipe from oil pan ( two bolts ). I also loosen the front sway bar driverside to reach plug.
6. Attempt to do w/carrier in service position.

Sounds like I did find the right plug, but it didn't look much like the diagram, and I didn't find any text description of its location. As difficult as it was to reach, I didn't want to go through the effort of accessing it if I wasn't sure I was in the right place. In hindsight, I don't think using the crank lock pin is all that necessary if you're reasonably careful.

For the lock carrier, I just suspended everything from the rafters with wire -- worked great.