My upper station steering went out but the lower station works ok and I am just starting to investigate. The wheel just keeps turning and does not stop unlike the lower one that stops after a few rotations. The "boatyarders" told me that it was just low on fluid. Cracked open the return bleeder valve and fluid began to leak out so I retightened. Cracked open the other valve on the top and tried to fill but it would not take any fluid. I tried turning the wheel a little in both directions and could see fluid actually come back up the filler tube. I put the valve back and could not see any evidence of any leak and it does appear that the steering pump is working and has fluid. Anybody have any suggestions? Any info in the mfg, schematic or any other info on your experience would be appreciated.