How to fix a Harbor freight 12 ton hydraulic jack

sujit roy

Hi Have 12 ton HF press. The jack that came with it, has stopped working and I can't figure out how to fix it. There an many YouTube videos but not on this type. This type has a plug on the side. Underneath the plug is a screw. I removed the screw and put back which I think was a no-no.  Does anyone know how to get this type working again? The jack without load seems to go up, but when load is applied it, bounces up and down at the same spot. 

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