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How to Bleed Air and Add Fluid to Your Hydraulic Floor Jack for Optimal Performance

  • Writer: Muddy Ruttzz
    Muddy Ruttzz
  • 12 hours ago
  • 6 min read

Why You Need to Bleed Hydraulic Floor Jack Air Bubbles Out


Welcome back to the Muddy Ruttzz Gazette!


A hydraulic floor jack is an essential tool for any home mechanic, but over time, or even right out of the box, air can get trapped inside the system. When this happens, your jack won't perform correctly—it might not lift a load efficiently, or it may slowly drift down after being pumped up.

There are a few key reasons why you might need to perform a procedure to bleed hydraulic floor jack air:

  • Initial Setup: You may have just purchased a new jack, and the oil level is slightly low, or a small amount of air has settled during shipping.

  • Oil Change/Refill: If you've changed the oil due to contamination or simply topping it off, you must bleed the system to ensure there are no air pockets introduced during the process.

  • Performance Issues: If you notice your jack isn't working smoothly or goes up and then slightly comes down, air trapped in the hydraulic fluid is the most common cause.

This process is straightforward and can be applied to most jacks, whether they are thirty years old like the one in my video or a brand-new model.


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Check Out My Youtube Video On This Subject Here


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Essential Tools and Materials


Hey there! Before you dive into the process, just a heads-up to grab the right stuff. Using the wrong fluid is a classic blunder that could mess up the seals and pistons inside your jack. So, let’s avoid that, shall we?

  • Dedicated Hydraulic Jack Oil: Do not use any other type of oil. Hydraulic jack oil is specifically formulated for this purpose.

  • Clean Rags: To manage any potential oil spills.

  • Small Funnel or Syringe: The filler hole on a floor jack is typically very small. I found that standard funnels often don't work, so I use a dedicated syringe (like one for bleeding bicycle brakes) to accurately add the oil without making a mess. Tip: If you use a syringe, keep it only for jack oil to prevent cross-contamination with brake fluid.

  • Owner's Manual (Recommended): The procedure is similar for most jacks, but it's always best to check the manufacturer's specific instructions, especially for newer models.


Person in gloves holding hydraulic jack oil near a jack. Text warns to use correct oil to prevent failure, injury, or death.
Don't mess around - use only real quality Hydraulic Jack Oil

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A person in gloves uses a syringe to add oil to a hydraulic jack on a workbench. Text: "Syringe Allows Adding Oil Without Spilling."
Syringe is One I Use For Bleeding Hydraulic Bike Brakes


The Step-by-Step Jack Bleeding Procedure


Performing a full bleed and oil top-off is a fast and easy maintenance task. Safety Note: Always work on a surface that can be easily cleaned in case of a small oil leak.


1. Prepare the Jack


The first step is crucial: you must relieve all pressure from the jack before attempting to access the filler plug.

  • Open the Release Valve: Fully open the release valve gear (turn it counter-clockwise) so the ram is fully lowered. When you pump the jack, the ram should not rise.

  • Locate the Filler Plug: The filler plug is typically a small rubber or metal cap located on the body of the jack near the oil reservoir.

  • Loosen the Plug (The First Air Release): Use a rag and slightly loosen the filler plug. You may immediately see and hear air bubbles coming out as the pressure is released. This is a good sign—it means the system is breathing.


Hydraulic jack on table, hand in black glove rotates handle. Yellow text: Rotate Handle To Turn The Release Valve Gear & Open The Valve.
This is a older Craftsman Floor Jack but modern jacks are usually similar. You may have a rubber plug instead of a screw. Opening the valve relieves pressure.
Person wearing gloves operates a 3½ ton hydraulic jack. Text: "Lay Handle Down To Access Fill Plug." Tools and label visible.
On the Craftsman laying the handle down shows the filler plug.


Gloved hand pointing at a hydraulic service jack's fill hole, highlighted by a red arrow and yellow label. Instruction label visible.
Lowering the handle provides access to the filler plug. Releasing the valve will make sure the jack does not pump when moving the handle.

2. Purge the Trapped Air


With the release valve open and the filler plug removed, you can now cycle the jack to force any remaining air out of the system.

• • Rapidly Pump the Handle: Pump the jack's handle rapidly several times (5 to 10 pumps) to push the air bubbles out through the filler hole.



Hand with glove using a red screwdriver on a fill hole screw, labeled with a yellow tag. Scratched metal surface in background.
Air bubbles may come out just by loosening the filler plug. Remove it to check fluid level.


Close-up of a machinery part with a fill hole screw. A red arrow points to it. Text reads "Fill Hole Screw." Image is in a greasy setting.
In this photo you can barely see air bubbles coming out of the filler hole.

3. Check and Top Off the Hydraulic Oil

After purging the air, you should check the oil level. In many older jacks, the oil can be so clear that it's difficult to see.

  • Add Fluid Slowly: Use your syringe or small funnel to add a small amount of hydraulic jack oil. The reservoir is considered full when the oil level is just below the edge of the filler hole, and it may start to overflow slightly.

  • Replace the Filler Plug: Once the oil is topped off and all air appears to be purged, carefully replace the filler plug and tighten it down to seal the reservoir.


Hydraulic jack with gloved hand pointing flashlight at fluid area. Text states difficulty in seeing fluid level due to clear fluid.
Place a rag or cardboard under the jack to collect any overflow Hydraulic Jack Fluid

Person in gloves uses a syringe to add hydraulic fluid to a 3 1/2 ton jack. Text reads "Syringe Is A Good Way To Add Hydraulic Fluid & Limit Spillage."
Syringe is a helpful too.

4. Test the Jack's Performance

The final step is to verify that the bleeding process worked and that your jack is operating optimally.

  • Close the Release Valve: Tighten the release valve gear (clockwise).

  • Pump the Jack Up: Use the handle to pump the jack up. A properly bled jack should lift the ram consistently with every single pump, rising by roughly the same amount each time.

If your jack is working smoothly, you're all set! Enjoy your fully functioning hydraulic floor jack.


Mechanic in plaid shirt and overalls repairing a black hydraulic jack. Tools and stickers visible in the workshop background.
Test the jack to make sure it operates smoothly

This article is a companion piece to my video, "How To Fill And Bleed A Hydraulic Floor Jack (Purge Air)." For a visual guide, be sure to check out the video on my Muddy Ruttzz YouTube Channel! You can also find more of my DIY and bike-related content on my blog at MuddyRuttzz.com.


Conclusion - Back Story - Safety


Borrowed a floor jack from a buddy who told me it was leaking. I said I would fix it. Little did I know floor jacks were fascinating tools and even a very old one could be rebuilt with a cheap rebuild kit. I found the exact floor jack on Craigslist and rebuilt that one and made a video for Youtube Muddy Ruttzz. Comments on that video made me realize a fill and bleed was something I should make.

If you fill your jack with oil or rebuild one be very careful using it. Always use Jack stands! Never rely on a jack to hold your vehicle up by itself. A seal or a o-ring could fail. Check out my jack rebuild video using this link: DIY Floor Jack Restoration: A Step-by-Step Guide (Resurrecting a Classic) https://youtu.be/GJZZFPAAxOg


Thanks for checking out my article and I hope it helps you out!


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Support Muddy Ruttzz in Producing Quality Content. Use My Links. I will get a small commission when you do. (No extra cost to you.) Does not matter if you purchase the linked product I get credit for anything you purchase within 24 hours. Thanks!


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✅ - Johnsens 5594 Hydraulic Jack Oil - https://ebay.us/8t7F3A (eBay)

✅ - Syringe For Fluid - https://ebay.us/uhL9be (eBay)

✅ - Buy A New Floor Jack on Ebay - https://ebay.us/ceREZ5 (eBay)



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As a Amazon Affiliate and Ebay Partner I receive a commission if you use my links to make a qualifying purchase. It does not raise the price you pay.






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