Well I've learned a bit about this in the last couple of days . . . I re-installed all of the hydraulic cylinders that I had rebuilt by Top Hydraulics, Inc. There ARE very small o-rings on the hydraulic line connectors that attach to the hydraulic cylinders. A broken / damaged o-ring is most certainly the cause of your leak . . . Klaus can send you some of those o-rings . . .

Please come back here to post on how you resolved your problem . . .