Im sure this one has been covered many times before. I just purchased a 48 8n. The hydralics would lift the finish mower about a foot when first started, after 30 minutes it would bleed down and would not raise. I thought this was a worn pump. I watched the youtube videos on the subject and then rebuilt the pump. first this i noticed was this looks like it was just done before but being there, I thought I would do it again for practice. I replaced both pump internals with a rebuild kit from capenters and replaced the lift pump piston and rings with the newer style. Filled it back up. The pump lifts all the way up without an implement on but will not budge the 4 ft finish mower. I can also stand on the lift arms and bring the lift back down while it is running- it will bring it back up right away. I am assuming I have a leak somewhere. I did take a look at the fluid tube leading to the lift piston and it was in good shape. Where should I start to look?