There are two types of hydraulic jacks, a floor and a bottle jack. A floor jack is a bottle jack laid on its side with different internal check valves and seals. The jack has six major components for its operation. A reservoir holds the fluid. The pump moves the fluid through a check valve that ensures a one-way flow of the hydraulic oil into the main cylinder. A ram piston is raised or extended by the fluid, and a release valve returns the fluid back into the reservoir after the jack has been used.
Vertical bottle jacks must be placed on a firm and level surface. A jack placed on a soft or inclined surface can tip over while it is placed under a load. The jack can literally kick out from its position and cause the load to fall. Bottle jacks should never be laid on their side or the ram upside down during operation. Air can enter the main cylinder and cause the jack to malfunction. Overloading the jack, or attempting to lift something heavier than it's rating, will cause the internal seals to break. Oil leaking from around the ram is an indication of a broken or blown seal.
Hydraulic oil or fluid should never have to be added to jack during its lifetime. Only when a leak has been identified should oil be added. In rare cases, when air has been introduced, can oil be added to relieve lifting problems. Typically there are three screw heads on a hydraulic jack. One is for adding fluid and two are the check valves. Never open the check valve screws. There are small parts that can be easily lost. The fluid fill screw is always located on the cylinder body. It is usually identified by the label "oil". Add oil into this location only. Allow the fluid to exit the hole to ensure the reservoir is full. The ram should be in the lower position.
On occasion, air may have been introduced into the main cylinder. In this instance raise the jacks ram to its full height and then lower the ram using the release valve. Open the fill oil screw slightly and listen for a small "psst" sound as air escapes. You may have to perform this operation a few times in order to remove all the air. Do not open the lower two screws that contain the check valves. This will only add air to the system.
