SLEEVE ASSEM. 5L4804 - Caterpillar

Probable Causes
Oil leaks from lines or connectionsRecommended Actions
Oil Leaks From Lines Or Connections
Check for leaks at fittings and connections of hydraulic lines/hoses. Leaks at fittings and connections on the suction side of pumps are a direct source of oil aeration. Oil aeration may cause damage (cavitation) to components and create excess or unusual noise. Correct any problems that are found then retest for the system.
Check for leaks at all fittings and connections of hydraulic oil hoses/lines/tubes in the system in question. Check all of the fittings and connections for proper torque on the suction side of pumps. Check all of the fittings and connections for proper torque on the negative pressure side of other motors and other components
Check the fluid level sight gauge on the side of the hydraulic oil tank. If the oil appears cloudy, check inside the hydraulic oil tank to ensure that the suction tube and the return oil tube are in place. Ensure that both are submerged in the oil (return oil splashing or spraying back into the tank can aerate oil)
Examine implement cylinder rod seals for signs of oil leakage or seeping. Worn or damaged seals may allow air to be drawn in when the rod end of the cylinder is below tank/ambient pressure. (such as during the blade "FLOAT" operation)
Loosen oil line connections after each hydraulic component (pressure side) and examine the oil for aeration at each inspection point. If the oil appears aerated as the oil seeps out of the loosened connection, that component may be the source of the aeration. The aeration may also be occurring some place between that component and the prior component that showed no signs of aeration
Examine the suction hose, the main suction manifold, and all suction lines. Examine the fittings, and connections from the suction manifold to the steering pump, the fan pump, and the implement pump. Look for indications of oil leakage. If oil leaks from these lines or connections when the machine is shut down, air will be drawn into the hydraulic oil system during operation. Air drawn into the system will cause the pumps to infuse the air and distribute the air to the components in that system/circuit. The aerated oil is then returned back to the tank
Ensure that the procedure to purge the air from the hydraulic system was completed correctly.