D5R2 and D6R2 Track-Type Tractors Hydraulic System Oil Temperature Is High Caterpillar

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

Use this procedure to troubleshoot high hydraulic oil temperature or use this procedure if one of the following event codes is active.

Probable Causes

• Oil cooler core is plugged or air flow over the core is low.

• Thermal bypass valve and/or cooler efficiency

• The hydraulic oil cooler leaks

• Viscosity of the oil is wrong.

• Oil contamination

• The hydraulic oil contains a large amount of air.

• System pressure is low.

• Oil level is low.

Recommended Actions

Note: Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the machine. You must be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component that contains fluid. Dispose of all fluids according to local regulations.

Oil Cooler Core Is Plugged Or Air Flow Over The Core Is Low

Check for restrictions in the core of the oil cooler. Air flow that is generated from the fan travels through the cooler fins to carry the heat away from the oil. High temperature can be caused by blockage of the fins of the cooler core. Ensure that the fins of the cooler core are clean. Ensure that the fins of the cooler core are not restricted. Check and clean any buildup of debris from the exterior of the cooler core, the fan, and/or the fan shroud. Clean the oil cooler core or repair the oil cooler core.

Periodically clean the cooling fins of the hydraulic oil cooler core. Material from the operating environment (such as wood chips, debris from landfills, or coal dust) can easily clog the fins.

Use a bent copper tube that is approximately 1/4 to 3/8 inch diameter as an extension to the air nozzle. This adaptation will facilitate cleaning of the middle spaces. Blow out the core with compressed air. Move the air nozzle in a systematic pattern so that the air flow covers the whole core that includes areas in the corner. Clean the middle space between the hydraulic oil cooler and the radiator cores.

Do not use steam or high-pressure water for frequent cleaning. Debris may be held deep in the cores. Use steam or high-pressure water in this case. Ensure that the cleaning is thorough. Partial removal or total removal of the hydraulic oil cooler may be required for better access.

Incomplete cleaning with water may cause remaining debris to harden in place. Use lights and wire probes to ensure that the cleaning is thorough and complete.

If the debris has hardened in the center of the cores, remove these cores for cleaning. If you use a degreaser and steam for removal of oil and grease, wash the core with detergent and hot water. Thoroughly rinse the core with clean water. Dry the cores completely before operating the machine in the work mode.

Thermal Bypass Valve And/Or Cooler Efficiency

Check the thermal bypass valve and/or cooler efficiency. If the thermal bypass valve of the hydraulic oil cooler is stuck in the OPEN position, the oil is not being directed through the cooling tubes. The hydraulic oil cooler is prevented from sufficiently cooling the oil. If the fins on the hydraulic oil cooler are clogged with debris, the hydraulic oil cooler may not be properly cooling the oil.

With an infrared thermometer, test the temperature of the cooler inlet and the cooler outlet. A temperature differential of at least 10 degrees should be observed, once the hydraulic oil is warmed to approximately 145°F (63°C). Closing temperature for the thermal bypass valve is 62° C (143° F) to 65° C (149° F). Opening pressure for the bypass valve is 620 kPa (90 psi) at 71° C (159° F). Replace the bypass valve if the temperature difference between the inlet of the bypass valve and the outlet of the bypass valve sufficient.

Note: If replacing the bypass valve does not correct the problem, the cooler core may be clogged with contaminants. This condition may be present after a catastrophic failure of a hydraulic pump, motor, or other hydraulic component that would release particles and contaminants into the system. The cooler core must be cleaned or the cooler core must be replaced.

Hydraulic Oil Cooler Leaks

Perform this inspection before cleaning the core.

Inspect the hydraulic oil cooler for leaks. Thoroughly examine all surfaces, tubes, and connections on the hydraulic oil cooler for signs of leaks. If oil is leaking, dirt and dust will adhere to the oily surfaces more than dry surfaces. Tighten any loose connections or fittings that might be leaking and recheck for leaks. The hydraulic oil cooler should be replaced if there are leaks on surfaces in addition to the fittings.

Viscosity Of The Oil Is Wrong

Ensure that oil is the correct viscosity for the operating conditions. To determine the correct oil viscosity, refer to the Operation and Maintenance Manual for your machine.

ReferenceFor D5R2 models, refer to the latest revision of Operation and Maintenance Manual, SEBU9258, "Lubricant Viscosities and Refill Capacities".

ReferenceFor D6R2 models, refer to the latest revision of Operation and Maintenance Manual, SEBU9246, "Lubricant Viscosities and Refill Capacities".

Oil Contamination

Ensure that the hydraulic oil is not contaminated.

Oil contamination may cause undesirable characteristics in hydraulic component operation due to the contaminants that cause changes to the oil viscosity.

Oil that is contaminated with dirt or other foreign particles can clog orifices and small passages. Contaminants may also cause moving parts such as valve spools to stick. Contaminants may damage the surfaces of mating parts that move against each other such as the valve spool and spool bore.

Oil that is contaminated with water will become cloudy and the viscosity will decrease. Over time the contamination will cause the oil to have an odor. Oil contaminated with water is also more spongy. This condition may cause a lag in cylinder movement and soft operation of components. An oil sample and subsequent oil analysis can determine if the oil is contaminated and the type of contaminants that are in the oil.

The Hydraulic Oil Contains A Large Amount Of Air

Ensure that the hydraulic oil is not aerated.

• Check all of the fittings and connections for proper torque on the following: suction side of pumps, 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. 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 seepage. Air may 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 occur 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. Check these components 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 air to the components in that system/circuit. Aerated oil is then returned back to the tank.

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

Oil aeration may be caused by a number of factors such as the following:

• low oil levels in the tanks

• cavitation in pumps or cylinders

• worn pump components (shaft seals, port plates, pump housing seals)

• leaks in the system on the suction side of pumps

Air in the oil can make the oil more spongy, causing a lag in cylinder movement. Air in the oil can cause erratic operation of hydraulic components.

Examine the hydraulic oil for signs of oil aeration. Aerated oil can appear cloudy if the air is finely spread in the oil. An oil sample and subsequent oil analysis can determine if the oil is aerated or if the oil is contaminated. If oil aeration is found, the source of the aeration must be located and eliminated.

Repair or replace any suspect components and then retest for the symptom.

System Pressure Is Low

Check the system pressure.

ReferenceFor D5R2 models, refer to the latest revision of Specifications, Systems Operation/Testing, and Adjusting, UENR4119, "Relief Valve (Main) - Test and Adjust".

ReferenceFor D6R2 models, refer to the latest revision of Specifications, Systems Operation/Testing, and Adjusting, UENR4109, "Relief Valve (Main) - Test and Adjust".

Oil level is low

Check the oil level. Add oil, if necessary. Refer to the Operation and Maintenance Manual for your machine.

ReferenceFor D5R2 models, refer to the latest revision of Operation and Maintenance Manual, SEBU9258, "Hydraulic System Oil Level - Check".

ReferenceFor D6R2 models, refer to the latest revision of Operation and Maintenance Manual, SEBU9246, "Hydraulic System Oil Level - Check".