793F AC Off-Highway Truck Hydraulic Fan and Steering System Caterpillar

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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.

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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, and the 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.

Introduction

The following instructions provide test and adjust information for the steering control valve.

This test will show the following conditions if the conditions exist.

• The steering control valve operates correctly.

• The steering control valve (3) is correctly set.

Tools Needed

Machine Preparation

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Sudden movement of the machine or release of air or oil under pressure can cause possible injury or death to persons on or near the machine. To prevent possible injury or death, do the procedure that follows before testing and adjusting the Hydraulic System.

1. Move the machine to a smooth horizontal location. Move away from any machines that are working and any personnel.

2. Move the shift control lever to the NEUTRAL position. Activate the parking brakes.

3. Fully raise the dump body of the truck.

4. Stop the engine. Move the engine start switch to the OFF position.

   Note: The pressure will not be released from the steering accumulators when you use the battery disconnect switch or the engine shutdown switch.

5. While the engine is not running, turn the steering wheel completely in both directions. Continue to turn the steering wheel in both directions until the front wheels will not move.

6. Turn the engine start switch key to the ON position. Do not start the engine. Turn the engine start switch key to the OFF position.

   Note: This process releases any pressure that is in the solenoid valve which is used to purge the accumulator. Refer to Operation and Maintenance Manual, "Steering Accumulator Pressure - Release" for more information.

7. Ensure that all air pressure and oil pressure is released before any fittings, hoses, or components are worked on.

8. Permit only one operator on the machine. Either keep other personnel away from the machine, or keep other personnel in the sight of the operator.

9. Place blocks in front of the wheels and behind the wheels.

10. Install the retaining pin for the dump body.

11. Make sure that the shift control lever is in the NEUTRAL position.

Test Procedure

The steering control valve must be tested on a bench test in order to achieve an accurate pressure test of each steering check and relief valve. The bench test is needed to meet the flow requirements.

Illustration 1	g01468988
Steering control valve that is located on the front of the steering support (1) Oil line to the steering cylinders for right turn "CR" (2) Oil line to the steering cylinders for left turn "CL" (3) Steering control valve

A functional test of the steering check and relief valves may be performed on the machine. Use the following procedure to test the steering check and relief valve in the right turn port.

Adjustment Procedure

1. Remove line (1) .

2. Install the plate assembly that fits a 25.4 mm (1.00 inch) hole in port "1".

3. Insert a tee and a pressure gauge before the quick coupler on the plate assembly or use the pressure gauge on the pump for the following test.

4. Install line (1) .

5. Connect the supply line from the hand hydraulic pump to the quick coupler on the plate assembly. Apply pressure.

6. Record the pressure that opens the steering check and relief valve. If the pressure reading does not fall in the acceptable range, replace the steering check and relief valve.

7. Check the steering check and relief valve in the left turn port with line (2) on steering control valve (3) .

Worksheet