824H Wheel Dozer, 825H Soil Compactor and 826H Landfill Compactor Electrohydraulic System Caterpillar


Torque Converter Stall and Implement Pump Double Stall - Test

Usage:

824H ASX

------ WARNING! ------

Personal injury or death can result from sudden machine movement.

Sudden movement of the machine can cause injury to persons on or near the machine.

To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

----------------------

The torque converter stall test helps determine if the engine is producing the correct power output. The torque converter stall test provides an engine speed for comparison with the engine speed from the double stall test. This stall test is used in many diagnostic procedures.

The service brakes must be applied when the tests are performed. Make sure that the service brakes and the parking brake are fully operational before you perform any tests.

Make sure that the transmission oil is at the normal operating temperature of 74° to 85°C (165° to 185°F) when any tests are performed.

  1. Park the machine on a smooth, level surface.

    Reference: For more information about preparing the machine for troubleshooting, refer to the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting".

  1. Turn the engine start switch to the OFF position.



    Illustration 1g00865617

    Location of the Solenoid Valve (Hydraulic Fan System)

    (1) Connector for the solenoid valve.

  1. Set the hydraulic fan to the maximum rpm. In order to run the hydraulic fan system at the maximum rpm, the connection to the solenoid valve for the hydraulic fan system must be disconnected.

    Note: The solenoid valve is located on the right side of the engine and below the hydraulic fan pump. Turn the engine start switch to the OFF position. Disconnect the wire harness from connector (1) on the solenoid valve (hydraulic fan).

  1. Shift the transmission to the NEUTRAL position. Start the engine. Engage the parking brake.

  1. Warm the transmission oil to normal operating temperature of approximately 74° to 85°C (165° to 185°F).

  1. Ensure that the work tool is positioned on the ground.

  1. Reduce the engine speed to low idle. Shift the transmission direction and speed control to the NEUTRAL position.

  1. Fully depress the right side service brake pedal. Place the transmission direction and speed control to the SECOND SPEED FORWARD position or in the SECOND SPEED REVERSE position. Hold the right service brake pedal in the depressed position for the duration of the test. Ensure that the parking brake is applied.

    Note: Do not use the left brake pedal as a service brake.




    Illustration 2g00865894

    Instrument Panel


    NOTICE

    To ensure that the transmission oil does not overheat, do not keep the torque converter in a full stall condition for more than 30 seconds. After the torque converter stall test, reduce the engine speed to low idle. In order to cool the oil, move the transmission control to the NEUTRAL position and run the engine between 1200 rpm and 1500 rpm.


  1. Slowly, depress the governor control pedal until the engine speed is at high idle. Allow the engine rpm to stabilize. Observe the tachometer and record the torque converter stall speed. The correct stall speed for the 824H, the 825H and the 826H is 1950 ± 50 rpm.

    Note: The results of the torque converter stall test must be within specifications before the double stall test can be performed.

    The double stall test is used in order to determine the performance of the implement pump. This stall test is also used in other diagnostic procedures.

  1. Shift the transmission direction and speed control to the NEUTRAL position.

    Note: Allow the engine coolant and the transmission oil to cool. Wait at least two minutes between tests in order to allow the transmission oil to cool.

  1. Ensure that the transmission oil is operating at normal operating temperature 74° to 85°C (165° to 185°F).

  1. Fully depress the right side service brake pedal. The transmission direction and speed control should be in second speed forward or in second speed reverse. Hold the right serviced brake pedal in the depressed position for the duration of this test. Ensure that the parking brake is applied.


    NOTICE

    To ensure that the transmission oil does not overheat, do not keep the torque converter in a full stall condition for more than 30 seconds. After the torque converter stall test, reduce the engine speed to low idle. In order to cool the oil, move the transmission control to the NEUTRAL position and run the engine between 1200 rpm and 1500 rpm.


  1. Move the joystick control to the full RAISE position. The blade will be in the full RAISED position. Hold the joystick control in this position.

  1. Place the transmission direction and speed control to the SECOND SPEED FORWARD position or to the SECOND SPEED REVERSE position. Slowly, depress the governor control pedal until the engine is at high idle.

  1. Allow the engine rpm to stabilize. Then, observe the tachometer and record the double stall speed. The correct double stall speed for the 824H, the 825H, and the 826H is 1862 ± 50 rpm.

  1. Move the control lever to the HOLD position. Reduce the engine speed to low idle. Shift the transmission direction and speed control to the NEUTRAL position.

  1. Release the right side service brake pedal.

    Turn the engine start switch to the OFF position. Connect the connector for the solenoid valve (hydraulic fan).

    Double stall speeds that are too high or too low indicate improper performance for the implement pump. The pump must then be tested.

    Reference: Refer to Testing and Adjusting, "Pump Performance (Implement) - Test" in order to determine the condition of the implement pump.

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