So yesterday after work I did an oil change on my daily driver and when I was done with that I thought I would spend an hour or so cleaning the mess off the used NV4500 I just picked up.
I got my engine hoist in position and realized it didn't lift.
This has happened before when I've left it outside. It gets water in it. I put my oil change bucket under it and removed the screw. Sure enough a milky water started coming out. I pumped it a bunch of times to help get all the contaminated oil out. Once I wasn't getting any oil out I put the ball and screw back in.
After I put new hydraulic jack oil back in it still doesn't work and I've never seen it do this before. It seems the check valve below the piston is stuck open.But only after the pump lever is used. If I lift the arm of the hoist manually and pump the lever a few times the arm will stay up and I can loosen the screw to bleed it back down. But if I pump the lever the arm only lifts as long as the lever pressure is maintained. Putting pressure on the arm also puts pressure on the pump lever.
I've never had this problem before so I'm assuming I will need to pull the cylinder apart but before I did I thought I'd see if anyone else has had a similar problem and what they did to fix it?