621H, 623H and 627H Wheel Tractor-Scrapers Braking and Hydraulic Fan System Caterpillar

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Always use a board or cardboard when checking for a leak. Escaping fluid under pressure, even a pin hole leak, can penetrate body tissue, causing serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury.

When you identify a problem, visually inspect the braking system, the hydraulic fan system, and the different components. Lower the bowl to the ground, lower the apron, stop the engine, and chock the wheels. Make the following inspections:

1. Trace all of the brake lines from the connections on the service brakes to the connections on the service brake control valve. Check the following components for damage and check the following components for leaks:
   • All of the brake lines

   • All of the connections on the components

2. Trace all of the hydraulic lines for the fan drive from the hydraulic fan pump to the hydraulic fan motor. Check the following components for damage and check the following components for leaks:
   • All of the lines for the hydraulic fan drive

   • The brake and the hydraulic fan pump

   • The hydraulic fan motor

   • The control manifold

   • All of the connections on the components

3. Check the control valves for leaks.

4. Check the following components for damage and check the following components for leaks:
   • The brake and the hydraulic fan pump

   • Control manifold

   • The connections on the components

5. Trace the lines from the brake and the hydraulic fan pump to the hydraulic tank. Also, trace the lines from the brake and the hydraulic fan pump to the control manifold. Check the following components for damage and check the following components for leaks:
   • The lines from the brake and the hydraulic fan pump to the hydraulic tank

   • The lines from the brake and the hydraulic fan pump to the control manifold

   • The hydraulic tank

   • The connections on the components

6. Check the hydraulic tank oil level.

7. Immediately after the machine has stopped, use a clean, clear bottle or use a clean, clear container in order to obtain an oil sample from the hydraulic tank. Check for air bubbles in the oil sample.

8. Remove the filter element. Check for particles that have been removed from the oil by the filter element. A magnet will separate ferrous particles from nonferrous particles. Ferrous materials such as piston rings contain iron. If necessary, replace the filter.

9. Locate the mesh screen that is located in the line to the diverter valve. Remove the mesh screen and check the mesh screen for debris. A magnet will separate ferrous particles from nonferrous particles. Ferrous materials such as piston rings contain iron. Clean the screen and reinstall the screen.