Hydraulic jack question

I got an old hydraulic jack. It is 10" high, 4.5" diameter, with a 2" piston. It is obvious that it has sat for a long time. It had some mud on the outside. Jack oil runs out the fill plug, and when I remove the turn screw, jack oil comes out the bottom. The pump pumps out the piston, but only a short way, then the pump becomes easy, leading me to believe it is low on oil. BTW, how much oil do I put in there? Up to the fill hole?

Should I just put some jack oil in there, or is there a process to flush, which may take out any water in there? Would some Marvel Mystery Oil harm the seals? Would there be another fluid to flush it with? Or should I just fill it with oil and call it good?

This appears to be an older one, not Chinese. Are these rebuildable? Out scrounging for cribbing for a new container, and found a volume tank for a compressor, too. Think I'll make a portable air tank out of that.

I love to go scrounging. Took my 86 yr. FIL, and he's just a big kid when it comes to puttering and scrounging.


Reply to
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Low on oil most likely. Take it apart, clean in suitable solvent, then reassemble and fill with fresh jack oil. Any hydraulic shop should be able to find suitable seals if needed.

Reply to
Pete C.

It had some mud on

remove the turn

the piston, but

to believe it is

the fill hole?

process to flush,

Mystery Oil harm

Or should I just

rebuildable? Out

volume tank for a

of that.

just a big kid when

Here's something to try before you do anything else. Pump it to the point where it stops then try pulling up on the ram as you pump and see if it begins to work again. There may be one area in the cylinder where the piston bypasses oil. That area may be corroded or else the jack has been overloaded and the cylinder is bulged at that point. phil

Reply to
Phil Kangas

Usually up to the bottom of the fill hole when the jack is standing vertically and the ram is fully retracted.

And you shouldn't be removing the lowering valve all the way, and it shouldn't leak from there - might need to change that seal too.

Try regular jack oil first, and it might take a cycle or three to purge any air from the ram. No solvents unless you totally disassemble and flush it - the volatiles stay behind and can attack seals, or otherwise affect long term reliability.

Sometimes - Tear it down and make sure the bones are solid (if the chrome plating on the ram is messed up repairs will cost more than the jack is worth) and you can get all the seals and gaskets you need first. No sense wasting effort if it's hopeless at the outset.


Reply to
Bruce L. Bergman

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