Does anyone know if the hydro system on a 2004 ferris hydrowalk sd is a sealed system? I just bought it used a couple of weeks ago and went to my dealer to order the hydro filter. I got home and went to change the fluid and don't see a filter on it Because it was used I don't have the manual for it and it is not on-line. The dealer looked it up on their system and it showed a filter but it's not there. Maybe he was looking at the wrong machine? Any help?