The bottle jack gets its name from the upright bottle shape of the cylinder. A bottle jack uses hydraulic pressure to lift large loads with little effort from the user. By pumping the jack handle, the ram is raised hydraulically from the cylinder, raising the load to the desired height. If your bottle jack no longer lifts loads or loses height after it has been raised, there may be air in the system that needs to be bled out.
Place the bottle jack in an upright position and wipe any dirt or oil from the exterior surface of the jack cylinder in the vicinity of the rubber oil plug. Push the ram into the cylinder fully by pushing on it with the palm of your hand.
Remove the rubber oil plug on the cylinder by prying it out carefully with the edge of a small flat-blade screwdriver. Set the plug aside.
Open the jack release valve by turning it with the jack handle in a counter-clockwise direction.
Insert the jack handle into its receptacle at the base of the jack cylinder and pump it in an up-and-down motion six to eight times to expel any trapped air in the system.
Replace the rubber oil plug into the cylinder by pressing it in with your thumb until the groove in the plug seats into the opening. Operate the jack as usual.
