Hydraulic floor jacks are capable of significant weight loads. Common hydraulic floor jacks can handle a few tons at a time. Lifting range can often run from 6 inches to 20 inches. The key to using a hydraulic floor jack, however, is not to overload it, but to center the load on the jack saddle and maintain it. Sometimes, if the jack isn't working as smoothly as it once did, you can overhaul it. Overhauling it includes replacing oil, lubrication and rest removal.
Determine whether the jack needs overhauling by raising the jack, lowering it and testing the hydraulics. Close the release handle by turning it clockwise, then raise the jack by pumping it. Maintain the raised position for a while and then open the release valve to lower the jack. If any of these operations are sticky or jerky, or the jack won't stay raised, it's an indication that oil isn't being drawn into the plunger cavity properly or you have poor hydraulic pressure. Overhaul the jack.
Remove all rusting with a wire brush and clean the surface of the jack with an oily rag to protect it.
Replace the oil. Release the valve gear assembly and remove the oil filer plug. Drain the oil by turning the jack over. Then refill with hydraulic jack oil, not hydraulic brake fluid, and open the release valve to expel air in the hydraulic chamber. Pump the jack handle a few times.
Lubricate all moving parts by coating them liberally with grease. Then test the jack.
