Things You'll Need
Hydraulic jack oil
Bottle jacks lift heavy loads. The mechanism must be placed in a level and vertical position for proper operation. If for some reason the bottle jack falls on its side and is left there for an extended period, the internal hydraulic oil may leak out. The hydraulic oil must be replaced to restore the fluid to its original level. An insufficient hydraulic fluid level may cause the jacking mechanism to fail while holding a load.
Drop the main piston on the hydraulic jack to the lowest position.
Turn the release valve clockwise to close the valve. The release valve is located at the bottom of the bottle jack.
Locate and remove the oil fill port. The oil fill port is located on the top two-thirds of the vertical housing of the bottle jack and is generally identified with the word "oil." Some bottle jacks may have a rubber plug or a slot head screw to seal the port.
Fill the jack with hydraulic jack oil through the port opening. Keep the jack in the vertical position. Continue to fill the jack until a small amount of oil seeps from the port.
Replace the port seal. Operate the jack mechanism to raise the piston to its full height. Open the release valve to lower the piston. Repeat several times to fully distribute the oil. Check the hydraulic oil level one more time to confirm the bottle jack is full of fluid after testing.
Never use brake fluid as a replacement for hydraulic bottle jack fluid. The alcohol in the brake fluid will destroy the jack's internal rubber O-rings.