I am sure is not oil level, we tried oil at different levels, even filling tank clear up. Checked all lines and fittings, all looked good, and as much air as this is getting I think a bad line or fitting would be leaking oil when tractor was not running. Can't really think it is water, had system clear empty, refilled with new oil, did the same thing.
I have a Farmpro 2430, but you said you "changed the filter and cleaned the screen on the pick-up line." Mine has no filter, but does have the fine screen in the lift box, so our tractors are not identical for some reason. I wonder of your filter is a problem somehow. I can't think where a man would put a filter on my Farmpro 2430, unless it was a high pressure filter. The "tank" line is internal to the lift box. The only place I could install one is on the suction line or the pressure line....and filters on the suction line are usually a no-no, and filters on the high pressure line are expensive, huge and heavy. Most filters go on tank lines, but there is no access to a tank line on my 2430 since the final pressure point of use is IN the lift box.
If you take a sample of the oil and put in a clear container, and mark the level on the side of the container, all it takes is time for the air to escape, and you have your diagnosis...the level drops a lot or a little, and the oil clears up, and you find no water separated out at the bottom. We have to do it sometimes at work. It is sort of fun..if you like mysteries...will I see water at the bottom, will the level drop, or will the oil be permanently milky. Hey..I'm paid for it...might as well view it as a mystery to solve.
I have never seen a case where the air will not leave the oil, but I have seen cases where the water will not separate, even in a centrifuge.
To get to the filter in the lift box, you had to remove that banjo fitting. At the end of that pipe with the banjo fitting, there is a bulkhead fitting under the belly of the tractor (used to support the pipe.) It could be that when you moved the banjo fitting out of the way, you damaged a seal in that bulkhead fitting. But if the problem existed before the screen was cleaned, make sure that pipe underneath didn't get nicked by a rock, etc.
Remember, air will go places that oil never thought about going...so your idea that it would be leaking oil is not necessarily correct. I have seen many things leak air but not oil. Different viscosity, and different adhesive and cohesive forces at play.
Suspect every seal at every junction, and also the quick connect if you have one in the suction line. Seals designed for pressure are sometimes used for low vacuum, but they may fail under those conditions since they rely (sometimes) on pressure to reinforce the seal.
On suction lines, sometimes I paint one area at a time with oil as a test. Sometimes oil will plug a small air leak INTO the suction line. If you paint an area, and the problem goes away for a little while, that is your problem area. And that painting process makes me look more carefully at the areas too.
Good luck, and if you want to compare notes on 2430's let me know.
