A hydraulic jack is a device used to lift heavy objects (usually cars or trucks). The system works by using oil to lubricate the internal mechanism. If you buy a new jack, it will come without oil, so you will need to fill it up. Cats also require oil refills every few years. First, you need to remove the cover plate and the fill plug. Then fill the chamber with hydraulic jack oil. Lastly, follow the procedure to bleed excess air into the system and leave the jack in good working order.
Steps
Part 1 of 2: filling the jack with oil
Step 1. Place the jack on a flat, level ground
This will prevent it from slipping while you work on it. Plus, you'll keep the oil level so you can accurately fill the chamber.
You should also place the jack somewhere that you don't mind getting dirty, in case you spill a little oil. If you don't want oil spilled in your driveway, try street work
Step 2. Open the discharge valve
This will lower the jack so you can access the fill plug. Each jack can have different discharge mechanisms. In some, the grip is lowered by turning the handle to the left. In others, you must press a dump valve at a different point.
- If you are not sure how to unload your cat, you can consult the owner's manual.
- Keep the dump valve open while you work.
Step 3. Remove the cover plate if your jack has one
Depending on your model, there may be a cover plate that protects the internal mechanism of the jack. Remove the screws that hold this cover in place. Then lift it up.
- Depending on the type of jack you have, the cover plate could come off completely or just lift off. If the plate comes off, store it in a safe place so it won't get lost.
- These screws generally require a Phillips screwdriver, but you can check your particular model to verify the type of screwdriver you need.
- Avoid losing the screws that you have removed. Store them in a safe place so you can put the cover back on later.
Step 4. Clean the area around the fill port plug
This port is where you should pour the oil. To avoid contamination, use a rag and wipe the area around the fill plug. This will prevent dirt from entering the oil reservoir.
If your jack is old and has a lot of dirt accumulated around the fill plug, use a hose or a pressure washer to spray and remove the dirt
Step 5. Remove the cap from the fill port
This item sits under the cover plate on most jacks. Depending on your model, the cap can be unscrewed or simply come off. If it is the screw type, use a screwdriver and turn it counterclockwise to remove the cap. If it just comes off, you can insert a flat screwdriver under the cap and lift it up.
- If you can't locate the fill port, you can consult your owner's manual.
- Be careful not to damage the cap when you remove it. If it doesn't come off easily, stop and re-evaluate what you're doing to avoid forcing it.
Step 6. Fill the reservoir with hydraulic jack oil
Pour in the oil until it is just below the bottom edge of the fill hole. Then stop. Wipe off any excess oil on the rim before replacing the plug.
- Use a funnel to avoid spillage.
- Avoid using substances other than hydraulic jack oil. Engine oil or brake fluid will not work.
Step 7. Replace the fill plug
Put the plug back into the hole or turn it clockwise to screw it in. Once the plug is in place, you should follow the procedure to bleed air from the hydraulic system.
- Do not attach the cover plate yet. You need to bleed the air out of the mechanism before continuing, so the cover plate will get in the way.
- Depending on the model, you may also need to keep the fill plug out while you bleed the air. Check your owner's manual for the correct process.
Part 2 of 2: Bleed the Air
Step 1. Confirm that the flush valve is open
The dump valve should still be open (since you filled the jack with oil), but you better be sure. Open the unloading mechanism fully to lower the jack. Leave the dump valve open while you bleed the air.
The bleeding process is important because air can build up inside the hydraulic system while you change the oil. If there is air inside the system, the jack will not lift properly and could even collapse. By purging it, you will remove the air and make the jack work properly
Step 2. Pump the handle rapidly 10-15 times with the dump valve open
This will push the air out of the system. With the discharge valve open, the jack should not rise while pumping. If it starts to rise, you should recheck to make sure the dump valve is open.
Some models have different variations on how to bleed the air. Check your owner's manual to see if your model uses a different method
Step 3. Close the flush valve and test the jack
Turn the handle clockwise to close the dump valve, then pump the jack. It should be raised with smooth, even movements. Pump it all the way up and then dump it.
If the cat wobbles or doesn't rise to the top, it probably still has air in its system. In this case, you must repeat the purging procedure
Step 4. Replace the cover plate
At the end of the process, you can reinstall all the parts you removed. Replace the cover plate and install it with the screws you removed earlier.
Warnings
- Never use any liquid other than hydraulic jack oil. Using the wrong oil can cause the cat to collapse.
- You should always consult the owner's manual before carrying out maintenance on your jack, as each model has different mechanisms.