938G Wheel Loader and IT38G Integrated Toolcarrier Hydraulic 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 securely. 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

Prepare the machine for testing by completing the procedure that is specified in the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.

Attach Test Equipment

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Illustration 1	g00301790
Location of Fan Drive Pump (1) Pressure tap. (2) Fan drive pump.

1. Fan drive pump (2) is attached to the front engine housing on the left side of the engine. Connect an 8T-0859 Pressure Gauge and a 177-7860 Hose Assembly to pressure tap (1) .

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Illustration 2	g00302989
Grill Assembly (3) Bolts. (4) Grill.

2. Remove eight bolts (3) and grill (4) .

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Illustration 3	g00302991
Finger Guard Assembly (5) Bolts. (6) Finger guard.

3. Remove two bolts (5). Remove finger guard (6) in order to access the fan blades.

Note: To check the speed of the fan drive motor, a 9U-7400 Multitach Tool Group must be used. The 9U-7400 Multitach Tool Group measures the speed of the fan drive motor by using reflective tape and a photo pickup.

4. If a piece of reflective tape is already visible on one of the fan blades, proceed to Step 5. If a piece of reflective tape is not visible on one of the fan blades, clean a small area on the surface of one fan blade. Then attach 50 mm (2.0 inch) of 1U-6605 Reflective Tape to the fan blade. Position the reflective tape so that the tape is completely visible.

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Illustration 4	g00302992
Placement of 9U-7400 Multitach Tool Group (7) Magnetic base. (8) Multitach Tool Group. (9) Photo pickup. (10) Fan drive motor.

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Illustration 5	g00760009
Fan Motor and Fan System Pressure Tap (11) 8T-0859 Pressure Gauge

5. Install finger guard (6). Install bolts (5) and tighten the bolts. Place photo pickup (9) into the holder on magnetic base (7) and tighten the screw. Attach magnetic base (7) to the fan guard assembly. When the reflective tape and photo pickup (9) are in alignment, the LED indicator (red light) will come on. Position photo pickup (9) accordingly. To check for correct alignment, use a long, narrow object to reach through the fan guard and manually rotate the fan.

   Reference: Special Instruction, NEHS0605, "9U-7400 Multitach II Group and 9U-7402 Multitach II Group"

   Note: The speed of the fan drive motor is more critical than the oil pressure.

Testing and Adjusting Procedure

1. Start the engine. Run the engine at high idle. Move the control levers in all directions in order to warm the hydraulic oil to normal operating temperature.

   Note: Vibration from the machine, air flow from the fan, and flexing of the fan blade may cause the photo pickup to become misaligned. It may be necessary to adjust the position of magnetic base (7) in order to realign photo pickup (9) .

2. Run the engine at high idle and record the reading on pressure gauge (11). This pressure reflects the relief pressure for the fan motor. Refer to Table 2 for the correct pressure setting. Record the speed that is shown on Multitach Tool Group (8). For the speed of the fan drive motor, refer to Table 2.
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   Table 2

   Machines	Fan System Pressure	Fan Speed
   938G Wheel Loader IT38G Integrated Toolcarrier	11200 ± 175 kPa (1625 ± 25 psi)	1300 ± 25 rpm

3. Stop the engine. If the speed and the system pressure of the fan drive system are within specifications, proceed to Step 5. If the speed and the system pressure of the fan drive system are not within specifications, proceed to Step 4.

4. Adjust the pressure relief setting on the pressure relief valve.

   1. If the machine is equipped with an externally adjustable relief valve, an allen wrench can be used to adjust the pressure relief setting for the fan drive motor. Adjust the pressure relief setting and then proceed to Step 2.

   2. If the machine is equipped with an internally adjustable relief valve, the pressure relief valve must be removed from the fan motor in order to adjust the pressure relief setting. Do not damage the sealing surfaces of the relief valve during the removal and installation. Remove the cap of the relief valve from the fan drive motor (10). The relief valve rests inside the cap. Remove the relief valve from the cap. Tighten the hex head bolt in order to increase spring tension. This will increase the fan drive system pressure and the fan motor rpm. Insert the relief valve in the cap. Install the cap on the fan motor. Finger tighten the cap. Tighten the cap to 26 ± 4 N·m (19 ± 2 lb ft) and then proceed to Step 2.

5. Disconnect the pressure gauge and the hose assembly. Remove all test equipment. Install the grill (4) and eight bolts (3) .