Sometimes portable automotive lifting devices like floor service jacks, bottle jacks and transmission jacks do not perform as anticipated when unpackaged. This is not uncommon due to the design of most hydraulic systems that power these jacks.
Although jacks are expected to operate properly right out of the box, it is not unusual for air to get trapped in the jack's hydraulic system due to shipping and/or handling. Oftentimes, jacks are shipped and/or handled upside down or on their sides. There are several symptoms of an air-trapped hydraulic system which include partial hydraulic pump stroke, not lifting a load, not sustaining a load or pumping feels spongy under load. These symptoms are not defects but rather indications a procedure for purging air from the hydraulic system must be performed. Air purging procedures differ depending on hydraulic power unit design and product type.
Procedures may be available in the jack’s owner's manual, from the manufacturer or the closest authorized service center. An air trapped hydraulic system may only have to be purged the first time it is used unless the jack is transported to a different location and in a position other than right side up.
Information provided by: PowerStation LLC