Hello, I recently picked up a 440 to have around my home. The possibilities seem endless with this little guy. I bought it from a guy that clearly didn't seem to know much about it. It has the Kohler17 engine that I tuned up and adjusted the governor, and it seems to be running pretty well. I had plans of doing a repower with one of the 22HP predator engines, but will wait for now. This is my first skid steer and I don't have a ton of experience with hydraulics. Everything "worked" when I bought it, and I didn't see any real leaks coming from it. The lift cylinders seemed to have a slight studder/pause when I raise them up, that seemed like some air in the lines to me. Yesterday, I was able to finally get it outside and give it a little workout for 30-40 minutes moving some chunks of wood/stumps, etc. I was generally pretty happy with it. When I was all done and putting it away in the garage, I cycled the lift and tilt hydros a few more times to see if maybe I did have air in the system. When I shut down the engine and used the pedals to release pressure, it almost sounded like some running water coming from the right side. I hopped out and noticed a bunch of oil leaking down the left side of the machine. Bummer. I figured that I had blown my first hose. (the hour meter shows 1508 hours and most hoses appear to be original) I've since spent quit a bit of time trying to trace back the leak. It seemed like a few quarts of oil at least, so surely it would be easy to spot the leak. No such luck. Naturally, the inside has not been cleaned in my years (or ever), so that makes it a bit more difficult, but I still could not spot anything. Originally, the oil level was little bit above the top mark, and after this leak it was closer to the bottom mark. So I decided to fire it back up and see if I could get it to leak more and again trace it back to the source. The lift still seemed like it had air in the system, but did function OK. I shut it off after a few minutes, but no leaks this time! I've been reading many posts on here and trying to study the service manual to understand how this machine operates as much as I can. The one suspicious thing I've noticed both times is that the reservoir appears to have TONS of air bubbles in it after I shut the machine down. This is now making me think that I have an air leak between the tank and hydraulic pump (or the pump itself), and that the fluid level raised up so much with all the air bubbles in it, that it just overflowed out of the tank. Does anyone have any other suggestions or ideas to try? One of the lift cylinders seems to seep out a bit of oil, but could air get sucked into the system any other way? Should there be bubbles at all in the hydro tank? I figured, even an air leak between the tank and pump would still seep out oil when the machine is not running? Thanks again for ant tips or advice. I'm loving this little guy and will be super happy when I get this particular issue resolved. PS, I forgot to add, that I have not changed the hydro oil or filter. I was going to try that this weekend to see if it makes any difference at all...or at least put a new filter on. I just don't know what oil is currently in there, and if I add something different, will it make a big difference. At only 4 gallon capacity, it seems like it might be worth it to just drain and replace.