Has anyone ever overhauled a hydraulic jack? I imagine it is similar to rebuilding a master cylinder and/or a brake caliper, but where do you get the parts? I was at the local flea market today, and saw a nice sturdy-looking 3 1/2 ton jack, made in China but branded "Michelin" with the Michelin man on it and everything. The guy wanted $50 for it. To make a long story short, after several people looked at it, it was determined that there is something wrong with it, as pumps right up with no load but won't lift any weight, so the guy ended up giving it to me for free, so he wouldn't have to take it home. I would like to fix it, if possible, because it seems to be a decent quality unit, and not even that heavily used---apart from some overspray, and a few minor scratches, it looks almost like new. Any suggestions would be much appreciated.

Today I finally got a chance to do something with the jack. I bought a quart of jack oil, intending to drain the old stuff out and replace it, but when I hoisted the thing out of the trunk, where it had been since last Sunday, just for the heck of it I shoved it under a nearby 240 and pumped the handle. Up it went, even after making contact with the crossmember, with no more than the normal amount of effort. Just to be sure, I left the front of the car raised about 6", for close to an hour, and it didn't budge. When I let it down, I was surprised with how smoothly and gradually it lowered (I've used plenty of other jacks that let go rather suddenly) It would seem there is nothing wrong with this jack, so I spent about an hour cleaning it up (lacquer thinner took the overspray right off, and didn't harm the original paint) and now it's ready to go.

So, the big mystery is, why didn't it work last Sunday at the flea market. The only thing I can think of is that it was tipped at an angle and some air got in where it shouldn't have been, and that riding around in my trunk for a few days, and/or my running it up and down a couple of times somehow bled it out. It's not like the guy trying to sell it had a huge truck that was too much for it to lift---I think it was a Tahoe, and he was only trying to raise one corner of it, which, if anything, should weigh less than the front of a 240.

Anyway, thanks to all who replied

I have one of these that I got new from Sam's Club about two years ago for about $65.

The one I have has the feature of quick rise and then changes internally for the heavy push.

I think two or three things could have happen.

Damage could have occurred to the closing valve, that the handle operates.

A gorilla on the end handle! I think of operator caused errors! It could have been strained and we know Chinese metals. It may be leaking past on the heavy load.

Next, the pump piston change over is suppose to happen. The shuttle valve is stuck or a check valve has trash in it.

It could be trash in the oil or low oil as others suggest.
Changing the oil or maybe a flush will fix it.

It is hard for this to work because the majority of the oil you have access to is the area around the main lift piston. That is the reservoir.

The oil level is established with the jack all the way down and the valve body end up on most jacks. Then it is filled up. I think that is how mine is done. As I remember it was awkward handling it to check to see if it was full from the factory.

Some disassembly may have to be done to the valve body.

Removing plugs of cross drilled holes to access the check balls. They are beneath the handle pistons and you will probably have to blow them out with compressed air. Cover all your holes and be ready to catch anything you can't see.

Another thought, you could remove the plugs and then pump the handle pistons by hand and be ready to catch the trash or parts while the oil is still in it. Either way be ready and watch for the order everything comes apart. Its all fairly simple but can get or will be a oily job.

This jack was meant to be yours! Good luck on your up lifting experience!

If you look closely at the bottle, or hydraulic system, you should find a plug. remove the plug, and allow the old fluid to drain out. then fill it with either mineral spirits, or varsol, and cycle the ram several times. drain this completely out, and refill with hydraulic fluid (from the parts house). If it does not leak from the ram seal, then you should be good to go.

I have fixed one just by cleaning it out. Sometimes the oil is really dirty and trash holds the poppet valves open a bit and they leak down. If you can empty out the oil, run a solvent through to rinse it then add clean oil, you may fix it. I have fixed a cheapie from asia that way.

What kind of solvent is suitable and won't harm the seals?

I was thinking it would be worth checking the oil level, but I didn't realize changing it would do any good. Isn't it a sealed system? How would dirt or debris get in? Does it require bleeding, and if so, how is it done?

It is pretty much self bleeding. There should be a fill port through which you might be able to drain much of the fluid.
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George Downs, Bartlesville, Heart of the USA!