A couple years ago the 2007-2012 Q7 and 2009-2012 Q5 were recalled to fix leaking fuel pump flanges. At the time, there weren't enough replacement flanges to go around. In a let's-see-if-this-works move Audi slapped some butyl tape around the existing flanges to prevent future leaks. It didn't.
Turns out if the flange has already been exposed to outside contaminates, covering it in tape will only prolong the inevitable leak. About 6,000 vehicles are being recalled again, hopefully this time for a more permanent repair.
Audi says plenty of replacement parts are now available to dealerships for technicians to install new fuel pump flanges, and butyl tape will again be applied to help protect the new fuel pump flanges from outside contamination.
This time the the butyl tape should work by preventing corrosive liquids from ever touching the new flanges in the first place.