Just had my car diagnosed for this same "gunk gunk" sound. They told me that it was the steering rack. Did some research and found out that there are two kinds of fluid that can be added to the power steering... Pentosin CHF 11 S(Green stick on resevoir cap), and ATF Dextron III(Black cap, no sticker). My green sticker fell off thousands of miles ago... I'm wondering if they added ATF fluid to mine, and if the mixing of the two fluids is what is causing the nosies coming from my steering rack? Any ideas?