5/21/2014 1:05 PM
Raise your units, then with each unit supported take off the hydraulic lines and cap them. Remove the supports and let the units rest, if one drops overnight, or both, then there is an internal leak within the cylinders. If they do not drop then they are good. What will happen is if they leak oil will go from one side of the piston to the other allowing them to drop. This will rule out your cylinders, or tell you that there is at least part of the issue. It will take you a little time to do, but it wont cost much and you don't need any special equipment other than some plugs and caps for you lines. You want the units as high as you can get when un-hooking them so you don't push any oil out, this way when they are capped you will have a fully raised cylinder. When seals go bad the oil is just passing back over the ram or piston allowing them to drop. If you have a warranty, or if they have replaced the lift/lower valve then that should at least have a parts warranty, I would have them replace it again. Not uncommon for those to go bad, or have a bad run of them from the manufacture. By the way, are all three dropping? Hope this helps. If you need any additional help feel free to shoot me an email. If I get time I'll dig up a schematic and take a look and make sure there isnt a check valve causing you issues.
Regards,