I know this is the Audi forums so I know you all love your Audi. I just got mine and in fact have not yet paid my neighbor for it so I could still get out. My question is this. I have offered and he has accepted $1200 US for the car in my sig. with 143K miles. I already have the front end off and am about to complete the water pump/ timing belt replacement, other than this one, clearly common, problem is the 2000 A6 a solid car? I feel like i am making a really good deal as the car looks very clean and with the exception of leaking water and running a bit rough seems to be in good working order. The windows, sunroof, door locks etc. all work. The timing belt is very lose on the bottom side near the tensioner so i feel sure the rough running was due in part to that. Anyway just looking for some reinforcement that I have made a good deal here....

 

You might want to perform a leak down test prior to putting the car back in service. If the cam belt is lose you could have bent valves. That would also cause rough running.

 

I assume a leak down test is a compression test where you leave each cylinder compressed and watch to see if the pressure drops over time? Are there any other "critical" or even suggested items i should replace while i have the front end off. I would rather take my time and spend a little more money right now and not have to worry about anything else for a while than to get this done and in 6 months have to do more work.

 

A leak down test will let you know the state of the engine better than a compression test, you can get a tester on Amazon. The problem with the AVK engine is that there is very little clearance between the center inlet valve and the piston crown. A lose timing belt or a couple of skipped teeth and it will contact the piston. The inlet valve has a very thin stem and it will bend.
I like the BlauParts enhanced timing belt kit, this has all the bits you need plus the camshaft and crank oil seals as well as a thermostat. I replaced all the crappy rubber vacuum lines with 4mm silicon vacuum line and the hard vacuum line with the Dorman 4mm hard line.. Check the PCV valve and it's plastic pipes at the back of the engine. They do tend to disintegrate with time and will cause a CEL.
You may want to replace the serpentine belt tensioner if is original, check that the tensioner roller bearing feels smooth, if not replace it.

 

Thank you. I posted more stuff on this car in the general tech section. I would be greatful if you would add your comments.