Pump is noisy but is spitting fluid out of the res cap. Level is fine. Cap is tight with good seal. Seems to be a relief in the cap for over pressure. Don't know much about Audis yet but I'm learning. It's a 2000 a6 4.2. Love some advice.
Thanks

 

I have same issue, we have swapped fluid, seems to be taking on air somewhere in system, then blowing out the vent in cap. Let me know if you find something.