IT38H Integrated Toolcarrier and 938H Wheel Loader Braking and Hydraulic Fan System Caterpillar

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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.

Machine Preparation

1. Move the machine to a smooth horizontal location. Move away from working machines and personnel. Lower the work tools to the ground.

2. Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.

3. Engage the parking brake.

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Illustration 1	g00893065

4. Place the steering frame lock in the LOCKED position.

   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.

5. In order to check the speed of the hydraulic fan motor, use a 9U-7400 Multitach . The multitach measures the hydraulic fan rpm 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 5. If no reflective tape is visible on one of the fan blades, use the following procedure:

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   Illustration 2	g00799694
   Side view of the radiator group

   1. Ensure that the key start switch is in the OFF position. Access to the fan blade is through door (1) on either side of the radiator group.

   2. Clean a small area on the surface of one fan blade. Position the reflective tape so that the tape is completely visible. Then attach a piece of the reflective tape to the fan blade.

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Illustration 3	g00815885

6. Place photo pickup (2) into the holder on magnetic base (3) and tighten the screw. Attach magnetic base (3) to the fan guard assembly.

7. When the reflective tape and photo pickup (2) are in alignment, the LED indicator (red light) will come on. Position photo pickup (1) accordingly.

   Note: When you start the engine, vibration of the machine may cause the photo pickup to become misaligned. It may be necessary to adjust the position of magnetic base (3) in order to realign photo pickup (2) .

Margin Pressure (Testing and Adjusting)

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Illustration 4	g01523133
Location of brake and fan drive pump

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Illustration 5	g01516151
(6) Margin Spool (7) High Pressure Cutoff Spool (8) Pump

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Illustration 6	g01528593

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Illustration 7	g01528751
(9) Load sensing port (10) Pump Discharge Port

Note: Ensure that the brake accumulators are fully charged before you begin the following procedure. While the brake accumulators are charging, high pressure will be at the load sensing port.

1. Connect 2 20000 kPa (2900 psi) pressure gauges to quick disconnects (9,10) on the pump discharge line and on the load sensing line.

2. Ensure that the hydraulic oil is at operating temperature. Place the transmission in NEUTRAL. Run the engine at high idle.

3. Connect the Caterpillar Electronic Technician (ET) service tool to the data link connector.

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Illustration 8	g01798255
Typical illustration

4. Select Series C6.6. Select "Diagnostics". Select "Diagnostic Test". Select "Override Parameters".

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Illustration 9	g01798537
Typical illustration

5. Select "Engine Fan Bypass"and change the value to 54%. This will provide the load in order to stroke the pump.

6. The difference between the two gauges is the margin pressure. The margin pressure should be 1800 ± 100 kPa (260 ± 15 psi).

7. If the margin pressure is out of the range, then remove the cap from margin spool (6) on the pump compensator. Adjust the margin spool until the differential is 1800 ± 100 kPa (260 ± 15 psi). Replace the cap on the margin spool.

High Pressure Cutoff (Testing and Adjusting)

1. Connect a 20000 kPa (2900 psi) pressure gauge to the quick disconnect on pump discharge line (10) .

2. Run the engine at high idle.

3. The pressure at the pump discharge port should be 18800 ± 690 kPa (2700 ± 100 psi).

4. If the pressure at the pump discharge port is not 18800 ± 690 kPa (2700 ± 100 psi), then remove the cap from high pressure spool (7) on the pump compensator. Continue to run the machine at high idle. Adjust the high pressure spool until the gauge reads 18800 ± 690 kPa (2700 ± 100 psi). Replace the cap on the high pressure spool.

5. Reconnect the fan solenoid when the adjustment is completed.

Hydraulic Fan Speed (Testing and Adjusting)

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Illustration 10	g01197352

1. Place the transmission in the NEUTRAL position. Engage the parking brake. Connect Caterpillar Electronic Technician (ET) to the diagnostic connector (11) .

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Illustration 11	g01516619

2. Start ET. When ET initializes, select the engine ECM from the choices that are available. Refer to Illustration 11.

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Illustration 12	g01516639

3. Check all Fault Codes under the engine ECM. Ensure that no faults are present in the fan drive system. Ensure that no faults are present with the hydraulic oil temperature sensor, the engine coolant temperature sensor, or the inlet manifold temperature sensor. If no faults are present, begin the calibration. Select "Service > Calibrations > Engine Cooling Fan Calibration". Refer to Illustration 12.

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Illustration 13	g01197346

4. The screen that is shown in Illustration 13 will appear. Follow the instructions on the screen. Click on "OK".

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Illustration 14	g01197350

5. The "Calibrations" screen will appear. Select both check boxes and click on "Begin".

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Illustration 15	g01197341

6. Ensure that the parking brake is set. Run the engine at high idle. Click on "Next" in the lower left corner of the screen.

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Illustration 16	g01197357

7. Continue running the machine at high idle. Use the photo tach to measure the fan speed. Adjust the current for the fan solenoid by using the arrows at the bottom of the screen. Increasing the current will decrease the fan speed. Decreasing the current will increase the fan speed. Adjust the current until the fan speed is 1620 ± 50 rpm.

   Note: If the machine is equipped with the variable pitch fan, set the fan speed to 1680 ± 50 rpm.

   Note: The procedure on the screen may specify a different value for the fan speed. Do not use this value. Set the fan speed according to the above instructions.

   When the fan speed has been set properly, click on the "Next" button in the lower left corner of the screen.

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Illustration 17	g01197355

8. After setting the maximum fan speed, click on "Continue" in order to set the minimum fan speed.

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Illustration 18	g01197354

9. Continue running the machine at high idle. Use the photo tach to measure the fan speed. Adjust the current for the fan solenoid by using the arrows at the bottom of the screen. Increasing the current will decrease the fan speed. Decreasing the current will increase the fan speed. Adjust the current until the fan speed is 500 ± 50 rpm.

   Note: If the machine is equipped with the variable pitch fan, set the fan speed to 550 ± 50 rpm.

   Note: The procedure on the screen may specify a different value for the fan speed. Do not use this value. Set the fan speed according to the above instructions.

   When the fan speed has been set properly, click on the "Next" button in the lower left corner of the screen.

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Illustration 19	g01197358

10. After setting the minimum fan speed, click on "Finish" in order to save calibration values. Exit ET.