if it had atf in it theres every possibility all the seals and valves are fooked, Vw do a rebuild kit for the rack its about 90 quid. If the fliud was anything but green its gonna have had atf even if its not all atf, and its known for destroying the seals, it does say only fill with green VW fluid and for once the warning isnt just so you go get genuine parts, its the only fluid that works :-) If you ask for steering fluid in a dealers they only do the one, and one bottle will fill the system, so maybe get 2 and empty, refill, circulate then empty again and refill with the second bottle. hope