I have a '96 450 skid steer, that I am having problems with the hydraulic filter, draining itself, back to the hydraulic tank. All the time..., I was thinking I had a sucton problem with the pump. Lift arms, and bucket jerky, like the pump was starving for oil... Pulled the hyd. tank, and checked for obstructions, and had a new suction hose made, in case of an unseen flap, or collapsed hose... Same thing....., and still foamy oil... The hyd. filter block made a slight squawl.., and has since I purchased it several months ago. Never owning one, I was thinking..., maybe it's the way it is.... Narrowed it down to air being trapped in the inverted filter. Called the local Bobcat shop foreman, and he said it SHOULD purge itself.... Went ahead and loosened the drain plug for the filter..., and poof!! A lot of air..!! Started it, and let it run for maybe 30 seconds..., and did it again... More air!! Refilled the oil tank, and did it again... More air..., but not as much... So figured I'd cycle it..., and work the rest out... Everything worked smooth as silk...., last night... After shutdown, kept hearing a gurgling sound, but could never trace it. Finally found it this morning!! The filter..., in it's inverted state, and probably 6-8 inches above the oil line in the resevoir, is draining back to the tank. When I started it up this morning..., same thing..., jerky on the lift arms, and bucket..., so air is trapped again... Seems a simple inline low pressure, high volume check valve would solve the problem.... If it were a rubber line, it may be an easy fix..., but it is a steel line... Still may try it... Did anyone ever own one of these, and have the same problem...?? Or was there ever a recall on these, to solve this issue...?? Do I have a faulty filter block, not allowing the system to purge the air from itself..., and allowing oil to drain back to the tank, once I did purge the system...?? By the time I found it, my local Bobcat dealer was closed.., and couldn't confer with the shop foreman. And trust me..., he's been good as gold to me this week!!! And he does know his stuff!! I'm just a poor dumb country boy.., but putting an inverted filter 6 to 8 inches above the full line in the tank, without a check valve..., is just asking for problems... It's pretty tough to push air down..., with a liquid..... Any ideas out here....?? Dave J.