D7E Track-Type Tractor Hydraulic, HVAC, and Electrical Systems Hydraulic System Oil Contains Air Caterpillar

Probable Causes

• Oil leaks from lines or connections

Recommended Actions

Oil Leaks From Lines Or Connections

Check for leaks at fittings and connections of hydraulic lines/hoses.

• 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 or on 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 hydraulic oil appears cloudy, check the inside of the hydraulic oil tank to ensure that the suction tube and the return oil tube are both in place and 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 which may allow air to be drawn in when the rod end of the cylinder is below tank/ambient pressure (such as during blade FLOAT)

• 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, 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, the connections will also draw air into the hydraulic oil system during operation. This condition will cause the pumps to infuse the air and distribute it to the components in that system/circuit and then return the aerated oil back to the tank

• Ensure that the procedure to purge the air from the hydraulic system was completed correctly.

Leaks at fittings and connections on the suction side of pumps are a direct source of oil aeration, which may cause damage to components (cavitation) and create excess or unusual noise, as well. Correct any problems that are found then retest for the symptom(s).