I have a curious oil leak on a new holland 1630 hydrostatic 1999 vintage. The engine oil is dark needing a change but is full and not requiring additional oil. the leak appeared to be hydraulic as it was coming from the hydrostatic case. The leak appeared to be coming from where the hydro pipe coming from the HST filter is going into the case on the left side of tractor. there is the pipe , an O ring, and the spring bracket for the brake pedal which holds the pipe into the HST pump. Now when I loosened the bracket holding in the pipe - I got a rush of fluid out of the hole the pipe goes through - about 1.3-1.5 gallons - all dark in color. Thought it might be that the HST filter was bad. when I removed the HST filter, the fluid there was crystal clear. When I finally pulled out the pipe - it too had clear fluid in it. So I opened the drain plug a little further back (the one to drain hydro fluid) - and got a flow of clear hydro fluid. So even after draining the hydro fluid - when I poked my finger into the HST Hydro pipe hole - there was more of the darkish fluid. So now the mystery - if the hydro drain is logically the lowest point in the hydro system - where is this fluid coming from? If all the hydro fluid is clear - why is the fluid in the HST case dark? Is there supposed to be fluid in that case?? Any ideas before I'm left with the only alternative is taking it to a new holland dealer (trhere are becoming fewer and fewer of them) for them to open up?