Challenger 35, Challenger 45 and Challenger 55 Agricultural Tractors Implement, Steering and Brake Hydraulic Systems Caterpillar

Check the Upstroke of the Steering Pump

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Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.

1. Move the machine to a smooth horizontal surface. Move away from other machines and personnel.

2. Permit only one operator on the machine. Keep all other personnel away from the machine.

Use the following procedure to test the steering control.

1. Stop the engine and remove the key.

2. Install the 6V-3989 Unvalved Nipples onto the 8T-0855 Pressure Gauges .

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Illustration 1	g00514240
(1) Pressure tap (2) Pressure tap

3. Use two hoses to connect two 8T-0855 Pressure Gauges to pressure taps (1) and (2).

   1. The two 8T-0855 Pressure Gauges are 0 to 4000 kPa (0 to 580 psi) pressure gauges.

   2. Pressure taps (1) and (2) are the pressure taps for the pilot oil from the steering control to the hydraulic displacement control valve.

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Illustration 2	g00514302
(3) Pressure tap for the right turn (4) Pressure tap for the left turn

4. Use two hoses to connect two 8T-0861 Pressure Gauges to pressure taps (3) and (4).

   1. The two 8T-0861 Pressure Gauges are 0 to 60000 kPa (0 to 8700 psi) pressure gauges.

   2. Pressure taps (3) and (4) are the pressure taps for the output of the steering pump.

5. Route the hoses into the cab so that the gauges are in the cab.

6. Start the engine. Run the engine at high idle.

7. Warm the oil to 60 °C (140 °F). At least two segments should be visible on the bargraph for hydraulic oil temperature.

8. Make sure that the transmission control lever is in the NEUTRAL position.

9. Test the hydraulic displacement control valve for the right turn.

   1. Slowly rotate the steering wheel to the right.

   2. The pressure at pressure tap (3) should begin to increase when the difference between pressure taps (1) and (2) is 400 kPa (58 psi).

10. Test the hydraulic displacement control valve for the left turn.

    1. Slowly rotate the steering wheel to the left.

    2. The pressure at pressure tap (4) should begin to increase when the difference between pressure taps (1) and (2) is 400 kPa (58 psi).

11. If the hydraulic displacement control valve is not operating correctly, adjust the deadband. Refer to "Adjust the Deadband".

12. If the deadband cannot be adjusted so that the hydraulic displacement control valve is operating correctly, the hydraulic displacement control valve must be serviced.

Check the Deadband

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Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.

1. Move the machine to a smooth horizontal surface. Move away from other machines and personnel.

2. Permit only one operator on the machine. Keep all other personnel away from the machine.

Use the following procedure to check the deadband of the machine.

1. Check the charge oil pressure. Make sure that the pressure is 2470 ± 170 kPa (358 ± 25 psi). Refer to Systems Operation/Testing and Adjusting, "Steering System Charge Oil Pressure Test".

2. Mark the steering wheel at the top center position. This is reference point "A".

3. Start the engine. Run the engine at high idle.

4. Warm the oil to 60°C (140°F). At least two segments should be visible on the bargraph for hydraulic oil temperature.

5. Move the transmission control lever to the NEUTRAL position.

6. Slowly rotate the steering wheel to the right until the machine begins to turn.

   1. Mark reference point "B" at this point.

7. The distance from point "A" to point "B" is the deadband for the right turn.

8. Slowly rotate the steering wheel to the left until the machine begins to turn.

   1. Mark reference point "C" at this point.

9. The distance from point "A" to point "C" is the deadband for the left turn.

10. Compare the deadband for the left turn to the deadband for the right turn. If the deadbands are uneven, adjust the deadband. Refer to "Adjust the Deadband".

Adjust the Deadband

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Personal injury can result from rotating and moving parts. Stay clear of all rotating and moving parts. Never attempt adjustments while the machine is moving or the engine is running unless otherwise specified. The machine must be parked on a level surface and the engine stopped.

Illustration 3	g00509652
(5) Hydraulic displacement control valve (6) Neutral adjustment screw

1. Make sure that the engine is stopped.

2. Loosen the locking nut on neutral adjustment screw (6) .

   1. The neutral adjustment screw is located on hydraulic displacement control valve (5) .

3. Rotate neutral adjustment screw (6) in order to adjust the deadband.

   1. Rotate the screw in increments of 30 degrees.

   2. Rotate the screw clockwise in order to increase the deadband for the right turn. This decreases the deadband for the left turn.

   3. Rotate the screw counterclockwise in order to increase the deadband for the left turn. This decreases the deadband for the right turn.

4. Tighten the locking nut on the neutral adjustment screw.

5. Check the deadband in order to ensure that the deadband is equal in both directions.

   1. Refer to "Check the Deadband".