Cavitation is a serious problem for hydraulic systems.  It occurs when the absolute pressure in a pump intake line is reduced below the vapor pressure of the fluid.

Hydraulic oil contains between 7 and 8 percent solubilized air.  Air bubbles are formed when these pressure changes occur, and these can cause cavitation.  As pressure increases, these bubbles or vacuum holes implode.  These implosions release great energy, and the internal temperature can reach 1,100 degree C.  Cavitation should not be taken slightly.  A cavitating pump can be totally destroyed in only a few hours, sometimes minutes.

Cavitation can be caused by the wrong pipe size on the inlet, cold operating temperatures and improper placement of the pump with respect to the reservoir (the pump should be placed as close to the reservoir as possible).  Cavitation usually occurs when the pump suction is being restricted.