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Rotating fan blades can result in personal injury or death. Stop the engine and allow the fan to come to a complete stop before making any test or adjustment. Before starting the engine, make sure all of the finger guards are installed and the guard door is closed. Do not allow any tools or test equipment to protrude or vibrate into the path of the rotating fan blades. |
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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand. |
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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock. |
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| NOTICE |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products. Dispose of all fluids according to local regulations and mandates. |
| Required Tools | ||
| Part Number | Description | Qty |
| 9U-7400 | Multitach | 1 |
Machine Preparation
ReferenceFor information about preparing a machine for troubleshooting, refer to the Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.
- In order to check the speed of the hydraulic fan motor, use a 9U-7400 Multitach . The multitach measures the hydraulic fan speed by using reflective tape and a photo pickup.
ReferenceSpecial Instruction, NEHS0605, "9U-7400 Multitach II Group and 9U-7402 Multitach II Group"
Note: If a piece of reflective tape is already visible on one of the fan blades, proceed to Step 2. If no reflective tape is visible on one of the fan blades, use the following procedure:
- Ensure that the key start switch is in the OFF position. Remove the grill assembly in order to access the fan blade.
Show/hide table
Illustration 1 g00867481
Location of the Fan
- Clean a small area on the surface of one fan blade. Position the reflective tape so that the entire piece of tape is visible. Then attach a piece of the reflective tape to the fan blade.
- Place photo pickup into the holder on magnetic base and tighten the screw. Attach the magnetic base to the fan guard assembly.
- When the reflective tape and photo pickup are in alignment, the LED indicator (red light) will come on. Position photo pickup accordingly.
Note: When you start the engine, vibration of the machine may cause the photo pickup to become misaligned. Adjustment of the position of magnetic base may be necessary in order to realign photo pickup.
Testing and Adjusting Fan Speed
Test and Adjust the Minimum Fan Speed
- Start the engine. Run the engine at low idle.
Note: In order to check the minimum fan speed at low idle, the following conditions must be met:
- The engine coolant must be less than 89 °C (192 °F).
- The temperature of the air inlet manifold must be less than 50 °C (122 °F).
- The temperature of the hydraulic oil sump must be less than 90 °C (194 °F).
- The engine coolant must be less than 89 °C (192 °F).
- Run the engine at low idle. Observe the multitach and record the hydraulic fan speed. The correct fan speed at low idle is 525 ± 50 rpm. Increase the engine speed to high idle in order to verify that the fan speed is 1350 ± 25 rpm.
- If the fan speed is not within the specifications, adjust the minimum fan speed. Use adjustment screw (1) on the hydraulic fan pump in order to adjust the minimum fan speed. Torque for the locking nut is 21 ± 2 N·m (15 ± 1.5 lb ft).
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| Illustration 2 | g00867437 |
Typical Example of a Hydraulic Fan Pump | |
- If any adjustments are made to the fan drive system, repeat Step 1 and Step 2 until the minimum fan speed is properly adjusted. After the minimum fan speed has been adjusted, proceed to Section "Test and Adjust the Maximum Fan Speed".
Test and Adjust the Maximum Fan Speed
| 824H, 825H, 826H Hydraulic Fan Speeds (1) | |
| Standard Ambient Cooling System | |
| Altitude | Target Max Fan Speed |
240 m (787 ft) |
1350 rpm |
500 m (1640 ft) |
1370 rpm |
1000 m (3281ft) |
1410 rpm |
1500 m (4921 ft) |
1460 rpm |
2000 m (6562 ft) |
1500 rpm |
2500 m (8202 ft) |
1550 rpm |
3000 m (9842 ft) |
1600 rpm |
3500 m (11483 ft) |
1650 rpm |
4000 m (13123 ft) |
1710 rpm |
4500 m (14764 ft) |
1725 rpm |
5000 m (16404 ft) |
1725 rpm |
| ( 1 ) | The hydraulic fan speed is at high RPM. Calibration of the Hydraulic Fan System is done through Caterpillar Electronic Technician. |
- Turn the engine start switch to the OFF position.
- The electrohydraulic control valve is located on the right side of the engine and below the hydraulic fan pump. Disconnect the electrical connector from the connection (3) on the electrohydraulic control valve.
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| Illustration 3 | g00867438 |
Electrohydraulic Control Valve | |
- Start the engine and run the engine at high idle.
- Observe the multitach and record the hydraulic fan speed. The maximum fan speed should be set according to the altitude and fan speed specifications listed in Table 2.
- If the speed of the fan is not within the specifications, adjust the maximum fan speed. Use adjusting screw (2) on the hydraulic fan pump in order to adjust the maximum fan speed. Torque for the locking nut is 21 ± 2 N·m (15 ± 1.5 lb ft).
ReferenceRefer to Illustration 2 for the location of adjusting screw (2) .
- If any adjustments are made to the hydraulic fan system, repeat Step 3 and Step 4 until the maximum fan speed is properly adjusted. Proceed to Section "Verification of the Demand Fan " in order to verify that the demand fan is working properly.
Verification of the Demand Fan
- Turn the key start switch to the OFF position. Connect the electrical connector to the connector on the electrohydraulic control valve (3) .
- Start the engine. Ensure that the hydraulic oil is at normal operating temperature.
- Check the operation of the demand Fan. Run the engine at high idle.
- In order to check the operation of the demand Fan, one of the following conditions must be met.
- The engine coolant must be greater than 89 °C (192 °F).
- The temperature of the air inlet manifold must be greater than 50 °C (122 °F).
- The temperature of the hydraulic oil sump must be less than 90 °C (194 °F).
Expect an increase of at least 100 rpm over the minimum setting.
- The engine coolant must be greater than 89 °C (192 °F).
- If the demand Fan is operating correctly, turn the engine start switch to the OFF position and remove all the test equipment. Install the grill assembly.