Can you replace a piston in a floor jack?

Question

My 3 ton floor jack doesn't lift. I do not see a leak, but there is no pressure. I checked everything I could see (didn't know what to do with the s***w that says "don't adjust". )

Can a replacement piston be bought for those or do you just buy a whole new jack?

Answer 1

Buy a new jack, but first make sure the valve you use to let it down with is really closed. The Do Not Adjust s***w should not be changed. That is the safety release that keeps you from trying to jack up a something too heavy with a small jack, that might collapse. One other thing you can check is the oil level, I know you said you didn't see any leaks, but it's worth checking. On the top side of the cylinder there should be a s***w or plug. It may be under a sheet metal cover, but should not require major dissasembly to get to. Open the plug and use a nail as a dipstick to check the level, it should be almost full. If it is low you can buy jack oil at most auto parts stores, leave a little room for air at the top. One other thing I have seen happen, If a jack is not stored right side up, it can get air in the pump. To get rid of that, open the release valve all the way, and operate the handle about twenty times. the close the valve and try it. Be careful with jacks, use good jack stands, like your life depends on it.

Answer 2

Your piston will be ok ,the bottom seal will have broken down ,letting the oil bypass the seal ,it will not show a leak ,you will need to un s***w the ring that fits round the piston at the top of the jack the piston will then pull out fo the jack with the top seal and bottom seal still on the piston ,renew both seals .

hope this helps you  

Answer 3

I know you don't want to hear this, but get a new jack.  Sounds like this jack has issues, could be older, a less than expert repair could lead to damage to your vehicle and or your body, not something you would want.