993K Wheel Loader Steering System Caterpillar

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Personal injury or death can result if two persons are not used in the following procedure.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause 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. Always use a board or cardboard when checking for a leak.

Reference: For the correct procedure to relieve any hydraulic oil pressure that may be in the steering system, refer to the Service Manual module for Testing and Adjusting, "System Pressure - Release" for the machine that is being tested.

1. Start the engine. Exercise the steering system in order to increase the hydraulic oil to normal operating temperature. Hydraulic oil temperature of steering system may be monitored through the VIDS/VIMS ELECTRONIC CONTROL or the Electronic Technician software.

2. Position the machine so that the machine is in the STRAIGHT AHEAD position.

3. Stop the engine. Lower the work tool to the ground.

4. Move steering frame lock to the UNLOCKED position. Engage the parking brake. Move the transmission direction selector to NEUTRAL.

Testing and Adjusting the Small Steering Pump

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Illustration 1	g01689893
(1) Pressure tap for the steering load signal line (2) Load sensing line for the large steering pump (3) Tee (4) Load sensing line for the small steering pump

1. Remove load sensing line (2) and place a cap over tee (3). Install 6v-9508 Plug and 6V-8397 O-Ring Seal onto load sensing line (2).
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   Illustration 2	g01621697
   Typical example of the installation of the differential pressure gauge

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   Illustration 3	g01689906
   Location for Pressure Taps

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   Illustration 4	g01689907
   Location for Steering Pump Pressure Tap

2. Connect the high pressure port (9) of the 1U-5796 Pressure Differential Gauge Group (7) to the pressure tap for the steering pump (1). Install a 40000 kPa (5800 psi) pressure gauge (5) at the high pressure port (6) of the 1U-5796 Pressure Differential Gauge Group. Connect the low pressure port (8) of the 1U-5796 Pressure Differential Gauge Group (7) to the quick connect port for the load sensing line for the main steering valve (2).

3. The margin pressure is the difference between the pressure of the load sensing line and the pressure of the steering pump output. Margin pressure must be taken while the machine is articulating. With the engine at high idle, command a partial steer to the left or right.

4. Start the engine and run the engine at high rpm. Move the STIC steering control lever to the LEFT TURN position or to the RIGHT TURN position. Continue to hold the STIC steering control in position until you are able to obtain a reliable pressure reading.

5. Record the pressure reading on the pressure gauge. The correct pressure should be 2100 ± 100 kPa (305 ± 15 psi). If the pressure is incorrect refer to Step 6 through Step 7.
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   Illustration 5	g01726537
   Small steering pump (11) Steering pump (12) Pump control valve (13) Locknut (14) Adjustment Screw

6. The pump control valve (12) is located on the side of the steering pump (11). The steering pump is located behind the operator's cab.

7. When you are adjusting the small steering pump, loosen locknut (13). Turn adjustment screw (14) clockwise in order to increase the steering system pressure. Turn the adjustment screw counterclockwise in order to decrease the steering system pressure. Hold the adjustment screw in place and tighten the locknut.

8. Stop the engine. Lower the work tool to the ground.

9. Release pressure in the steering system.

10. Remove the hose assembly and the pressure gauge from the pressure tap.

11. Remove the cap, 6v-9508 Plug and 6V-8397 O-Ring Seal. Place load sensing line (2) onto tee (3).

Testing and Adjusting the Large Steering Pump

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Illustration 6	g01689893
(1) Pressure tap for the steering load signal line (2) Load sensing line for the large steering pump (3) Tee (4) Load sensing line for the small steering pump

1. Remove load sensing line (4) and place a cap over tee (3). Install 6v-9508 Plug and 6V-8397 O-Ring Seal onto load sensing line (4).
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   Illustration 7	g01621697
   Typical example of the installation of the differential pressure gauge

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   Illustration 8	g01689906
   Location for Pressure Taps

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   Illustration 9	g01689907
   Location for Steering Pump Pressure Tap

2. Connect the high pressure port (9) of the 1U-5796 Pressure Differential Gauge Group (7) to the pressure tap for the steering pump (1). Install a 40000 kPa (5800 psi) pressure gauge (5) at the high pressure port (6) of the 1U-5796 Pressure Differential Gauge Group. Connect the low pressure port (8) of the 1U-5796 Pressure Differential Gauge Group (7) to the quick connect port for the load sensing line for the main steering valve (2).

3. The margin pressure is the difference between the pressure of the load sensing line and the pressure of the steering pump output. Margin pressure must be taken while the machine is articulating. With the engine at high idle, command a partial steer to the left or right.

4. Start the engine and run the engine at high rpm. Move the STIC steering control lever to the LEFT TURN position or to the RIGHT TURN position. Continue to hold the STIC steering control in position until you are able to obtain a reliable pressure reading.

5. Record the pressure reading on the pressure gauge. The correct pressure should be 2100 ± 100 kPa (305 ± 15 psi). If the pressure is incorrect refer to Step 6 through Step 7.
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   Illustration 10	g01689909
   Large steering pump (15) Steering pump (16) Pump control valve (17) Locknut (18) Adjustment Screw

6. The pump control valve (16) is located on the side of the steering pump (15). The steering pump is located behind the operator's cab.

7. When you are adjusting the large steering pump loosen locknut (17). Turn adjustment screw (18) clockwise in order to increase the steering system pressure. Turn the adjustment screw counterclockwise in order to decrease the steering system pressure. Hold the adjustment screw in place and tighten the locknut.

8. Stop the engine. Lower the work tool to the ground.

9. Release pressure in the steering system.

10. Remove the hose assembly and the pressure gauge from the pressure tap.

11. Remove the cap, 6v-9508 Plug and 6V-8397 O-Ring Seal. Place load sensing line (4) onto tee (3).