Challenger 35, Challenger 45 and Challenger 55 Agricultural Tractors Power Train Caterpillar

Detension the Track

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High pressure cylinder. Parts can separate with explosive force if proper care is not used during disassembly. This can cause injury or death. Do not disassemble any part of this cylinder until you have read and understand the instructions given in the service manual. Observe the instructions given in the service manual.

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Illustration 1	g00336815

1. Connect the hose group to the upper, left implement hydraulic coupler (1).

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Illustration 2	g00495110
Accumulator (A) for the belt tensioner. (PIN: 8DN1-619) (PIN: 1DR1-1400) (PIN: 7DM1-657)

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Illustration 3	g00495111
Accumulator (B) for the belt tensioner. (PIN: 8DN620) (PIN: 7DR1401) (PIN: 6DM658)

2. Tighten all hand valves on the hose group. Remove the cap from nipple (2) on the belt tensioner. Connect the hose coupler.

   Note: If you cannot connect the hose group to the nipple, there may be a buildup of hydraulic pressure between the filler valve and the nipple. In order to release the pressure, see "Release the Pressure Between the Nipple and The Filler Valve".

3. Place the implement control lever in the FLOAT position.

4. Open all hand valves on the hose group.

5. Slowly open filler valve (3) by a maximum of one turn in order to release the pressure from the belt tensioner into the implement hydraulic system.

6. After the pressure from the belt tensioner is fully released and cylinder rod (4) stops moving, you may need to push the front idler rearward in order to fully retract the belt tensioner.

7. Close fill valve (3) and remove the hose group.

Fully Tensioning an Open System

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High pressure cylinder. Parts can separate with explosive force if proper care is not used during disassembly. This can cause injury or death. Do not disassemble any part of this cylinder until you have read and understand the instructions given in the service manual. Observe the instructions given in the service manual.

Illustration 4	g00336840

Use the following procedure to purge air from the hydraulic system for the belt tensioner. Air becomes trapped if the system has been opened for repair or replacement of components.

1. Verify that filler valve (1) is closed.

2. Repeat Step 1 and Step 2 in "Detension the Track" in order to connect the hose group.

3. Open purge valve (2) by 1/4 turn to 1/2 turn.

4. Direct oil drain hose (3) into a suitable container. If necessary, add more hose to the oil drain hose.

5. Start the engine. Run the engine at LOW IDLE. Hold the implement control lever in the RAISE position.

6. Slowly open filler valve (1) by 1/2 turn to 1 turn. This allows the belt tensioner to fill. Also, this purges air from the oil drain hose. When no large bubbles remain in the drain stream, tighten bleeder valve (2) to a torque of 28 ± 7 N·m (21 ± 5 lb ft).

7. Continue charging the system until a system pressure of at least 17225 kPa (2500 psi) is indicated by the pressure gauge.

8. While you maintain the implement control lever in the RAISE position, close the hand valve on the hose group in order to isolate the pressure gauge and the belt tensioner.

   Note: Perform Step 9 through Step 11 in order to test for the correct nitrogen pressure in the accumulator. Complete Step 9 through Step 11 whenever you detension the belt tensioner or you service the belt tensioner.

9. Place the implement control lever in the FLOAT position. Stop the engine.

10. Open the hand valve on the hose group by a small amount in order to relieve the hydraulic pressure from the belt tensioner.

11. Watch the pressure gauge closely. Observe when a sudden decrease in hydraulic pressure occurs. The last pressure value that was observed before the sudden decrease indicates the nitrogen pressure in the accumulator. The nitrogen pressure should be between 10000 kPa (1450 psi) and 14100 kPa (2050 psi).

    Note: If the amount of the decrease in pressure is greater than 1380 kPa (200 psi), the measurement of nitrogen pressure will be incorrect. Repeat Step 9 through Step 11 at a slower rate until the decrease is less than 1380 kPa (200 psi).

12. A low nitrogen pressure may indicate that an accumulator is damaged. You may need to replace the accumulator. The problem should be corrected before you operate the machine. Use the 9U-6740 Gas Charging Kit in order to recharge the accumulator.

13. Start the engine. Run the engine at LOW IDLE. Hold the implement control lever in the RAISE position.

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NOTICE
The track tensioning mechanism contains a hydraulic accumulator which acts as a spring to maintain track tension. Check the accumulator pressure whenever the track is adjusted or repaired.

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NOTICE
A rupture disc is used as a pressure release in the charging manifold for the track tensioner. Hydraulic oil pressure can increase because of low nitrogen pressure in the accumulator. In the event of tensioner overpressure, this disc will vent oil and relieve all track tension. Replace any accumulator that will not maintain nitrogen pressure.

14. Open the hand valve on the hose group and allow the system to charge for a minimum of 50 seconds.

    Note: The belt may appear to be tensioned almost immediately after you begin to charge the belt tensioner. However, a minimum of 50 seconds is required to ensure the correct charge for the belt tensioner.

15. While you hold the implement control lever in the RAISE position, close the hand valve on the hose group in order to isolate the pressure gauge and the belt tensioner.

16. Place the implement control lever in FLOAT. Stop the engine.

17. Verify that the pressure gauge reads 18950 ± 520 kPa (2750 ± 75 psi). If the pressure is low, repeat Step 14 and open the hand valve on the hose group in order to continue charging the system for an additional 50 seconds.

    Note: If 18950 ± 520 kPa (2750 ± 75 psi) cannot be achieved, the relief pressure of the implement hydraulic system may be low. Refer to Systems Operation/Testing And Adjusting, "Implement Pump Pressure Discharge Pressure Test".

18. Tighten filler valve (1) to a torque of 28 ± 7 N·m (21 ± 5 lb ft).

19. Open the hand valve on the hose group in order to relieve the pressure in the hose. Disconnect the hose group.

    Note: This process should charge the belt tensioner to a pressure of 18950 ± 520 kPa (2750 ± 75 psi). After you operate the machine, the pressure of the belt tensioner may decrease by approximately 1380 kPa (200 psi). The pressure decreases because of extension of the belt tensioner after the belt seats into the components of the undercarriage. This is normal. You do need to recharge the belt tensioner.

Fully Tensioning a Closed System

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High pressure cylinder. Parts can separate with explosive force if proper care is not used during disassembly. This can cause injury or death. Do not disassemble any part of this cylinder until you have read and understand the instructions given in the service manual. Observe the instructions given in the service manual.

Illustration 5	g00336840

Use the following procedure in order to charge a belt tensioner that does not have trapped air. You may need the following procedure when you remove belts or when you install belts. Also, you may need this procedure when you change the track gauge.

Note: When you use a new hose group, remove the air that is trapped in the hose. See "Fully Tensioning an Open System".

1. Verify that filler valve (1) and purge valve (2) are closed.

2. In order to connect the hose group, perform Step 1 and Step 2 in "Detension the Track".

   Note: If you cannot connect the hose group to the nipple, there may be a buildup of hydraulic pressure between the filler valve and the nipple. In order to release the pressure, see "Release the Pressure Between the Nipple and The Filler Valve".

3. Start the engine. Run the engine at LOW IDLE. Hold the implement control lever in the RAISE position.

4. Slowly open filler valve (1) by 1/2 turn to 1 turn. This allows the belt tensioner to fill. Continue charging the system until a system pressure of at least 17255 kPa (2500 psi) is indicated by the pressure gauge.

5. While you maintain the implement control lever in the RAISE position, close the hand valve on the hose group in order to isolate the pressure gauge and the belt tensioner.

   Note: Perform Step 6 through Step 8 in order to test for the correct nitrogen pressure in the accumulator. Step 6 through Step 8 must be completed whenever you detension the belt tensioner or you service the belt tensioner.

6. Place the implement control lever in the FLOAT position. Stop the engine.

7. Open the hand valve on the hose group by a small amount in order to relieve the hydraulic pressure from the belt tensioner.

8. Watch the pressure gauge closely. Observe when a sudden decrease in hydraulic pressure occurs. The last pressure value that was observed before the sudden decrease indicates the nitrogen pressure in the accumulator. The nitrogen pressure should be between 10000 kPa (1450 psi) and 14100 kPa (2050 psi).

   Note: If the amount of the decrease in pressure is greater than 1380 kPa (200 psi), the measurement of nitrogen pressure will be incorrect. Repeat Step 10 through Step 12 at a slower rate until the decrease is less than 1380 kPa (200 psi).

9. A low nitrogen pressure may indicate that an accumulator is damaged. The problem should be corrected before you operate the machine. Use the 9U-6740 Gas Charging Kit in order to recharge the accumulator.

10. Start the engine. Run the engine at LOW IDLE. Hold the implement control lever in the RAISE position.

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NOTICE
The track tensioning mechanism contains a hydraulic accumulator which acts as a spring to maintain track tension. Check the accumulator pressure whenever the track is adjusted or repaired.

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NOTICE
A rupture disc is used as a pressure release in the charging manifold for the track tensioner. Hydraulic oil pressure can increase because of low nitrogen pressure in the accumulator. In the event of tensioner overpressure, this disc will vent oil and relieve all track tension. Replace any accumulator that will not maintain nitrogen pressure.

11. Open the hand valve on the hose group and allow the system to charge for a minimum of 50 seconds.

    Note: The belt may appear to be tensioned almost immediately after you begin to charge the belt tensioner. However, a minimum of 50 seconds is required to ensure the correct charge for the belt tensioner.

12. While you hold the implement control lever in the RAISE position, close the hand valve on the hose group in order to isolate the pressure gauge and the belt tensioner.

13. Place the implement control lever in FLOAT. Stop the engine.

14. Verify that the pressure gauge reads 18950 ± 520 kPa (2750 ± 75 psi). If the pressure is low, repeat Step 11 and open the hand valve on the hose group in order to continue charging the system for an additional 50 seconds.

    Note: If 18950 ± 520 kPa (2750 ± 75 psi) cannot be achieved, the relief pressure of the implement hydraulic system may be low. Refer to Systems Operation/Testing and Adjusting, "Implement Pump Pressure Discharge Pressure Test".

15. Tighten filler valve (1) to a torque of 28 ± 7 N·m (21 ± 5 lb ft).

16. Open the hand valve on the hose group in order to relieve the pressure in the hose. Disconnect the hose group.

    Note: This process should charge the belt tensioner to a pressure of 18950 ± 520 kPa (2750 ± 75 psi). After you operate the machine, the pressure of the belt tensioner may decrease by approximately 1380 kPa (200 psi). The pressure decreases because of extension of the belt tensioner after the belt seats into the components of the undercarriage. This is normal. You do need to recharge the belt tensioner.

Release the Pressure Between the Nipple and The Filler Valve

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High pressure cylinder. Parts can separate with explosive force if proper care is not used during disassembly. This can cause injury or death. Do not disassemble any part of this cylinder until you have read and understand the instructions given in the service manual. Observe the instructions given in the service manual.

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Illustration 6	g00336980

1. Verify that filler valve (1) is tightened to a torque of 28 ± 7 N·m (21 ± 5 lb ft).

2. Loosen nipple (3) by a maximum of one turn. It is normal for a few drops of oil to leak around the threads. After you wait at least 30 seconds, tighten nipple (3) .

   Note: If a significant amount of oil leaks from the nipple or sprays from the nipple, immediately tighten the nipple. This indicates a malfunctioning filler valve. You must use purge valve (2) in order to safely discharge the belt tensioner.