How to Bleed a Hydraulic Jack
A hydraulic jack is a pressurized system that consists of six simple parts: a pump, check valve, release valve, main cylinder, ram piston and reservoir. Bleeding jacks is not routine maintenance the way it might be on the braking system of a car. Occasionally, a bad seal may introduce air into the system, and you will need to bleed it. Be sure to understand the correct position of the filler port before attempting to bleed your jack. Does this Spark an idea?
Instructions
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Check all the seals to see if they are worn, loose or need replacing if the jack is acting spongy. Tighten the seals, and if needed, unscrew the nut at the bottom of the shaft and replace with new seals.
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Prepare to bleed the system by positioning the jack all the way into the up/out position.
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Discharge the release and retract the hydraulic jack all the way into the down position.
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Open the filler port plug on the jack, and listen for air escaping, being very careful NOT to open a check valve by mistake. Opening a check valve will cause air to be sucked into your system. See the Resource section for a bird's eye view of Lincoln/Walker, Hein-Werner and Asian models of the hydraulic jack for placement of the filler port plug. They are easy to confuse with the check and overload valves on the system.
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Occasionally you will lose the prime of your jack when inexperienced persons have been improperly handling it. Close the release valve, pull up/out on the piston, re-open the release valve and force it back down again. This motion should push the oil through the workings and allow the piston to catch the prime. Repeat the operation several times, if needed.
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Tips & Warnings
Hydraulic jacks do not consume fluid; if you are low, check the seals.
Opening the check valve can be dangerous and may render your system inoperable.
