How to Add Oil to a Hydraulic Floor Jack. A hydraulic floor jack is a device used to lift heavy objects or to apply force. Instead of screw threads employed by standard mechanical jacks, hydraulic jacks use hydraulic cylinders to create high linear forces. Hydraulic jacks use an incompressible and self-lubricating fluid, typically oil, that is forced into a cylinder with a pump plunger to build pressure. If you want to keep your hydraulic floor jack functioning properly, you need to learn how to add oil to its mechanism.
Place the floor jack on a flat, even and dry surface. Open the release valve to ensure that the jack is in the down position. This will allow the remaining oil to flow back to the main reservoir at the bottom of the jack. There might be minor oil leakage.
Locate the oil plug, which is usually somewhere near the top of the oil reservoir. Inspect the plug for leakage and wipe it off thoroughly with a soft, clean cloth. Unscrew the oil fill plug with an Allen wrench or a large screwdriver, depending on the type of floor jack. Remove the oil fill plug and set it aside.
Insert a small funnel in the oil filler hole and start adding the oil. Pour until the level of oil is 1/8-inch from the neck of the oil filler hole. The type of oil used in this step can vary. Consult the manufacturer’s instruction manual for recommendation.
Reinstall the oil filler plug and use the cloth to wipe any oil residue around the neck.
Raise the hydraulic floor jack by pumping the handle until it is in the full up position. Then check the ram piston for any major oil leakage. If you don’t see more than a few drops, it means that the oil seal is functioning and that the process was a success.
Wipe away any oil residue from the ram piston and other parts of the floor jack with a soft, clean cloth.
Raise and then lower the hydraulic floor jack a few times. This will eliminate air bubbles from the oil.