Fixing a floor jack that won't stay up
 

I have a 3T floor jack that pumps up, but won't hold. It starts to settle back down as soon as I stop the pump stroke. No, I'm not overloading the jack.

What's wrong? Does it just need to be bled or what?

It did this a bunch of years ago but seemed to self correct after leaving it alone for a real long time. It was working great, but got left outside back in the fall and got wet. I pulled it into the garage when I realized it was outside, but didn't try to use it until recently. I had to break out a bottle jack.

If your fluid level is good, then the seals are shot. If you know the brand, you can usually find a rebuild kit. If you don't know the brand you will have to take it apart and take all the seals and gaskets to a bearing house to have them matched up. If the main piston is scored from rust (left outside) it sould probably be cheaper and easier to replace it with a new unit.

It's a Sears and is a really good jack except this that's happened twice now. I'll check the fluid level. I never leave the jack up or use it harshly, so the piston should look pretty good. I'll check that too though.

A piece of dirt or debris can become lodged under a check ball and cause the same thing. Change oil and flush it out with some hydraulic oil, NOT BRAKE FLUID! ATF would work OK.

Sears should have rebuild kits for it, they will need serial number to locate the kit. You could try changing the oil, couldn't hurt.

don't count on Sears having the rebuild kit, they didn't for mine.........about a '79 model
was able to clean, replace o-rings by matching, replace oil (used hydralic jack oil from Tractor Supply)
works fine now

Outstanding job, and be careful when jacking......lol.

A little viagra will help the seals swell back up :)