My 2003 A4 quattro 3.0 has a loud "groaning" noise when turning the wheel, most noticable at slow speeds. Power steering fluid was just flushed and filled (it was low, but no leaks were detected), problem went away for 24 hours and now back again. Fluid is at maximum level. Have complained to dealer on several occations about this, they don't seem to have a clue. Any ideas?