A hydraulic jack serves as a device utilized for hoisting heavy loads, typically cars or trucks. Its functionality relies on oil to lubricate the internal mechanism. In the case of acquiring a new jack, it arrives devoid of oil, requiring filling. Additionally, jacks necessitate periodic oil refills. Initially, remove the cover plate and filler plug. Subsequently, fill the chamber with hydraulic jack oil. Finally, follow the procedure to purge excess air from the system, ensuring optimal functionality of your jack.
Procedures
Refilling the Hydraulic Jack with Oil

Position the jack on a flat, level surface. This prevents unintended movement during the refilling process and facilitates accurate oil level assessment.
- Place the jack in an area tolerant of potential spills, such as the street, if avoiding oil stains on your driveway is desired.

Engage the release valve. This action lowers the jack to facilitate access to the filler plug. Different jacks may feature varying release mechanisms. Some jacks require counterclockwise rotation of the handle to lower the pressure, while others necessitate pressing a release valve located elsewhere.
- If unsure about your jack's release mechanism, refer to the owner's manual.
- Maintain an open release valve during the procedure.

Detach the protective cover plate if present. Depending on the model of your jack, it might include a cover plate shielding its internal mechanism. Remove any securing screws holding the cover in position, then lift off the cover.
- Depending on the jack type, the cover plate may either fully detach or lift up. If removable, store it safely to avoid misplacement.
- Typically, Phillips head screwdrivers are suitable for removing these screws, but verify your specific model's requirements.
- Keep the removed screws safe for later reattachment of the cover.

Clean the area surrounding the filler port plug. The filler port serves as the entry point for oil. Use a cloth to wipe the area around the filler plug to prevent contamination and keep dirt out of the oil reservoir.
- For older jacks with accumulated dirt around the fill plug, consider using a hose or pressure washer to dislodge the debris beforehand.

Extract the filler port plug. Typically located beneath the cover plate on most jacks, the plug may either unscrew or pop out, depending on the jack model. For screw-type plugs, utilize a screwdriver and rotate counterclockwise to remove. For pop-out plugs, insert a flathead screwdriver underneath and lift.
- If unable to locate the filler port, consult the jack's owner's manual.
- Exercise caution to avoid damaging the plug during removal. If encountering resistance, halt and reassess rather than forcing removal.

Refill the reservoir with hydraulic jack oil. Pour oil until it reaches just below the lower rim of the fill hole, then cease pouring. Wipe off any excess oil from the rim before reinstalling the plug.
- Utilize a funnel to minimize spillage.
- Strictly employ hydraulic jack oil for this purpose; other oils such as motor oil or brake fluid are not suitable.

Reinsert the filler plug. Either push the plug back into position or screw it clockwise to secure it. Once the plug is in place, proceed to purge air from the hydraulic system as per the outlined procedure.
- Delay replacing the cover plate for now. Air bleeding remains necessary before proceeding, and the cover plate could hinder the process.
- Depending on your jack model, it might be necessary to keep the fill plug out during air bleeding. Refer to your owner’s manual for the correct procedure.
Air Bleeding Procedure

Ensure the release valve remains open. While the release valve should still be open from the oil filling stage, verify its status. Fully open the release mechanism to lower the jack and keep it open during air bleeding.
- Air bleeding is vital to remove air buildup in the hydraulic system, which can impede proper jack operation. Failure to bleed air might result in improper lifting or even jack failure.

Rapidly pump the handle 10-15 times with the release valve open. This action expels air from the jack system. With the release valve open, the jack should remain stationary while pumping. If it begins to rise, double-check the release valve status.
- Various jack models may have different air bleeding methods. Consult your owner’s manual to ascertain the appropriate procedure for your model.

Seal the release valve and assess the jack's performance. Rotate the handle clockwise to close the release valve, then pump the jack. It should ascend smoothly and uniformly. Pump it to its maximum height, then release.
- If the jack operates jerkily or fails to reach its full height, air likely remains in the system. Repeat the air bleeding process if necessary.

Reinstall the protective cover plate. With the procedure completed, proceed to replace all removed components. Position the cover plate back onto its designated spot and secure it using the previously removed screws.
Essential Supplies
- Screwdriver (flathead or Phillips)
- Hydraulic jack oil
- Rags
Useful Pointers
Important Reminders
- Only utilize hydraulic jack oil for your jack; using any other liquid can lead to jack failure.
- Prior to performing maintenance on your jack, always refer to your owner’s manual as different models may feature distinct mechanisms.