How To Bleed A Hydraulic Jack

April 15, 2022

Jack floor fail to lift.

Any substance that impairs the right functioning of the hydraulic fluid is considered a contaminant, and for this reason, when air gets entrained in hydraulic fluid, you need to engage in corrective action to prevent damage to the system components and fluid. Moreover, it is dangerous to use a floor jack with air entrained in its system, for air is also a contaminant that can degrade the equipment’s performance. 

Furthermore, the air is expandable and compressible and can prevent the smooth fluid flow within the system. To do away with air in your hydraulic jack, you need to bleed your floor jack, and this task is fairly simple, which even a handyman can handle.

Why is Bleeding Your Floor Jack Very Important?

You need to bleed your hydraulic jack occasionally if you want it to perform within its peak capacity. You need to bleed your hydraulic jack if you are using it heavily for some time. You should also bleed it if the jack is on its side for a time or you have transported it over a substantial distance, for there is a big chance that a few air bubbles have been entrained into its fluid system. Remember that even a tiny amount of air in the operating fluid of your hydraulic jack can diminish its performance. 

The presence of air can limit the hydraulic jack’s maximum lifting capacity. It can also cause a slight sag after it lifts a load, which can be very annoying or deadly to the one operating the jack. Hence, it is crucial that you become cognizant of how to bleed your hydraulic jack.

Steps on Bleeding Hydraulic Jack

Below are the simple steps on how to do it:

Step 1; Ensure that Your Hydraulic Jack is in a Retracted Position

Before you tinker with your hydraulic jack, it will be useful to ensure that all its components are in a fully retracted position. You need to make sure that its landing gear, slide-outs, and stabilizers are retracted inside the unit as if it is about to travel.

Step 2: Check Its Fluid

Next, you should locate the hydraulic pump’s fluid and note the fluid amount in its reservoir. You should take note that its fluid level must be about a quarter of an inch from the reservoir’s top and should not be more than half an inch from the top. 

After checking the fluid level and ensuring that you have retracted all hydraulic components, you should check for any froth, bubbles, or foam on the fluid’s top. Such a presence of bubbles is indicative of the fact that air has been entrained onto the reservoir when you retracted the components in the last cycle. 

So, try to wait for 15 to 20 minutes for the bubbles to dissipate before you begin bleeding the hydraulic jack.

Step 3: Extend the Ram Piston

Support your jack up until you extend the ram piston fully. The ram piston is the jack’s part directly located beneath the load it is lifting. It is necessary that you completely extend the ram piston before you can work on it. 

Step 4: Jack’s Pressure Valve

Now that you have extended the ram piston, you can now safely release the pressure valve to lower the jack. You will find the pressure valve on the jack’s side. You can release it with a flathead screwdriver. 

Attach to the valve your screwdriver. Afterward, turn it counterclockwise. Once done with this step, you may continue with the next step.

Step 5: Turn Open the Filler Plug

Once you’re done releasing the pressure valve, you can now open up the filler plug. You can find the filler plug on the main body of the jack. However, it will be helpful not to confuse the filler plug with that of the check valves. In case you are confused about where the filler plug is located, it will help to check the instruction manual. The check valves should be left untouched. 

Upon locating the filler plug, you can attach the flathead screwdriver and work on it in a counterclockwise fashion. Slowly turn the screwdriver. Once you’ve removed the filler plug, you would hear a hiss indicating that the trapped air is escaping through the plug. You can reattach back to the jack the filler plug once the hiss stops.

Step 6: Repeat the Process Until There is No More Air!

Once you have reattached the filler plug, you can go on repeating the same steps until you are sure that no air is seeping out. Once you have bled the floor jack, you can use it.


The air present in the operating fluid of your hydraulic jack may compromise your work and safety. As such, you should not renege in regularly bleeding your hydraulic jack as long as it needs bleeding. Remember that air is expandable and compressible. 

As such, its presence in the fluid may cause expansion or compression, which are two things you don’t like to happen to your hydraulic fluid. Moreover, it can impede the right flow of fluid within the system. 

Having air in the hydraulic fluid may prevent the right lifting of the load while limiting the jack’s carrying capacity. Thus, it can either be very annoying or fatal if accidents happen.