How do you bleed a hydraulic jack?

Answer 1

http://www.hyjacks.com/H7.HTM is a simple description of how a jack works, and how to service one. Best info I could find and it worked for me. If the link is no good for some reason, it says to put the jack on a flat level surface and jack it all the way up, drop it back down, then open the FILL plug located on the side of the cylinder. Don't remove the screws on the base or springs and check balls may come out. If it's a bottle jack, the plug will be about 2/3 of the way up the side of the cylinder. On a floor jack with a horizontal cylinder it will be on the top, or slightly off center from top, anywhere along the cylinder body. The location of the plug is significant because it indicates the proper fluid level. It may hiss a little as you unscrew the fill plug (or pry it out with a screwdriver if it is a rubber plug). Look in the hole and make sure the level is good. It should be right up to the fill plug hole. If it's low, run to the parts store and get some jack oil (yup, they have it) and top it off. Put the plug back in and run the jack through another up/down cycle. It should work noticeably better. You might have to do this drill 1 to 4 times before the jack feels solid and goes all the way up. If the oil level was very low, it may get "Foamy" and you may have to allow a few minutes between each cycle for air in the oil to settle to the top. If this doesn't work the jack likely needs repair to the check balls or pump. Jacks are designed to work in specific orientations, always use and store your jack right side up.