A pressure test could identify it if you could see the water pump. I believe the pump is run by the timing belt on the 2.0L and under a cover. Plus, when you say it leaks after it's turned off makes me believe that even more. You see, when the engine is hot and running, water circulates keeping the engine cool. When you shut it, the circulation stops and the coolant sits in one spot almost boiling. Thus, it builds the most pressure then.
If you are going to a VW dealer, they should be fine with an Audi. Just make sure they have checked the water pump. Just to give you an example of how hard it is to get to one, the first thing you need to do to work on it is to gain access to the front of the engine, the front bumper must be removed and the hood lock carrier assembly moved forward to the service position. If you have the 1.8L I believe it is run by a serp belt.
Let me know which engine you have so I can be more exact.
PS: For some reason, your response didn't come to me directly. The group moderator sent it to me, so I'm sorry it took so long to get back with you. I always check my email, morning, afternoon, and evening. It's 9:30 PM here now so time to hit the sack, but I will check my mail in the AM by 9:00.
Monday, February 23rd, 2009 AT 8:32 PM