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| Illustration 1 | g00294551 |
(1) Hydraulic oil filter bypass valve. (2) Hydraulic oil cooler. (3) Hydraulic oil cooler bypass valve. (4) Hydraulic oil filter. (5) Fan drive pump. (6) Breaker relief valve. (7) Fan drive motor. (8) Hydraulic oil tank. (AA) Fluid sampling valve. (BB) Pressure tap for the fan drive pump. | |
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| Illustration 2 | g00294553 |
Location of the Fan Drive Pump (5) Fan drive pump. (BB) Pressure tap for the fan drive pump. | |
Fan drive pump (5) is mounted on the right side of the engine toward the rear of the machine. The pump only draws oil from the hydraulic oil tank when the engine is operating.
Pressure tap (BB) is available to check the pressure setting of the relief valve in the fan drive motor.
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| Illustration 3 | g00294554 |
Location of the Fan Drive Motor (7) Fan drive motor. (9) Return line from the fan drive motor. (10) Case drain from the fan drive motor. (11) Supply line to the fan drive motor. | |
The fan drive pump supplies oil to fan drive motor (7). The high pressure of the oil causes the fan blades on the shaft of the fan drive motor to rotate. The rotation of the fan causes cool air to flow through the hydraulic oil cooler. The flow of air cools the hydraulic oil in the hydraulic oil cooler.
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| Illustration 4 | g00294555 |
Location of the Hydraulic Oil Cooler (2) Hydraulic oil cooler. (3) Hydraulic oil cooler bypass valve. | |
After the hydraulic oil exits the fan drive motor, the oil flows to hydraulic oil cooler (2). When the engine is first started and the hydraulic oil is cold, the oil from the fan drive motor can not easily flow through hydraulic oil cooler (2). The oil pressure increases in the hydraulic oil cooler and hydraulic oil cooler bypass valve (3) opens.
Because of the resistance of oil flow through the oil cooler, the oil flows through hydraulic oil cooler bypass valve (3). Bypass valve (3) limits the maximum oil pressure in the hydraulic oil cooler to 448 ± 55 kPa (65 ± 8 psi). Any oil that flows through bypass valve (3) flows to the hydraulic oil filter.
When the temperature of the oil increases, and the pressure of the oil decreases, the force of the spring in hydraulic oil cooler bypass valve (3) is greater than the force of the oil pressure that is acting on the spring. This allows bypass valve (3) to close. The hydraulic oil then flows through hydraulic oil cooler (2) to the hydraulic oil filter.
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| Illustration 5 | g00294558 |
Location of the Hydraulic Oil Filter (1) Hydraulic oil filter bypass valve. (4) Hydraulic oil filter. (12) Bypass switch for the hydraulic oil filter. (AA) Fluid sampling valve. | |
After the oil exits the hydraulic oil cooler, the oil flows to hydraulic oil filter (4). Hydraulic oil filter (4) is located above the hydraulic oil tank on the right side of the machine.
If hydraulic oil filter (4) becomes plugged, the oil pressure in the filter increases. Once the oil pressure in the oil filter reaches approximately 172 kPa (25 psi), hydraulic oil filter bypass valve (1) opens.
Oil that flows through bypass valve (1) returns to the hydraulic oil tank. When the bypass valve opens, bypass switch (12) sends an electrical signal to the Caterpillar Monitoring System. The Caterpillar Monitoring System warns the operator of a fault in the hydraulic oil filter.
Fluid sampling valve (AA) is available to check the quality of the hydraulic oil.
Reference: For more information on checking the pump pressure and fan motor speed, refer to the Service Manual module for Testing and Adjusting, "Fan Drive Speed - Test and Adjust" for the machine that is being serviced.
Reference: For more information on obtaining a hydraulic oil sample, refer to the Operation and Maintenance Manual, "S·O·S Oil Analysis" for the machine that is being serviced.