992K Wheel Loader and 854K Wheel Dozer Steering System Caterpillar

Show/hide table

Personal injury or death can result from machine articulation or movement. Machine frames can move and a person can be crushed. Connect the steering frame lock link between the front and rear frames before working on machine.

Show/hide table

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.

Show/hide table

The drive shaft rotates between the torque converter and the transmission whenever the engine is running. Contact with the rotating shaft can result in personal injury or death. The rotating shaft is located under the implement and steering pumps. Do not allow personnel into the pump bay area behind the cab when the engine is running.

Note: There are two procedures that must be performed to check steering pilot oil pressure. The first procedure is for checking the actual pilot oil pressure from the steering pilot pump. The second procedure is for checking the pilot oil pressure from the primary steering pump. To check the pilot oil circuit correctly, perform both procedures.

The design of the steering system on this machine allows the pilot oil for the steering system to have a primary source and a secondary source. When the steering system functions correctly, the steering pilot pump is the primary source of pilot oil. Additionally, this pump supplies the oil for the cooling circuit for the steering system and for the braking system.

Oil pressure from the steering pilot pump is controlled by a relief valve. The steering pilot relief valve limits the pilot oil pressure to 2400 ± 150 kPa (350 ± 20 psi). This pressure should be checked at low idle engine speed.

To allow the steering system to work efficiently, the pilot pressure must be adjusted correctly. If the steering pilot relief valve is adjusted too low, several problems could occur. A lack of pilot oil pressure will cause the primary steering pump to supply the pilot oil instead of the steering pilot pump. Also, there may not be enough oil flow through the oil cooler toadequately cool the hydraulic circuits.

If the steering pilot relief valve is adjusted too high, several problems could occur. Excessive pilot pressure could cause damage to the pilot control valve in the cab. Excessive pilot pressure could also cause steering to be jerky or erratic. Additionally, excessive pilot pressure could demand more power from the engine.

However, the steering pilot pump may be unable to provide adequate pilot oil pressure for the steering system. If this happens, the secondary source provides the pilot oil pressure. The secondary source is the primary steering pump.

When the primary steering pump provides the pilot oil for the steering system, the pressure oil flows through a pressure reducing valve. The pressure reducing valve decreases the oil pressure from pump pressure to pilot oil pressure. The pressure reducing valve limits the pressure of the pilot oil to 1650 ± 150 kPa (240 ± 20 psi).

If the pressure reducing valve on the steering control valve is adjusted too low, several problems could occur. There could be an inadequate amount of pilot oil pressure for the steering system when the steering pump must supply the pilot oil. If this happens, operation of the STIC steering control lever may be slow or the STIC steering control lever may not be responsive at all.

If the pressure reducing valve on the steering control valve is adjusted too high, several problems could occur. The steering pump may become the primary source of pilot oil for the steering system instead of the steering pilot pump. If the pilot pressure is too high, damage to the pilot control valve may result. Excessive pilot pressure could also cause steering to be jerky or erratic. Additionally, excessive pilot pressure could demand more power from the engine.

If a machine is equipped with secondary steering, the secondary steering pump supplies oil pressure for the pilot oil circuit. This will only occur if the primary steering pump and the steering pilot pump stop working. The pressure oil from the secondary steering pump flows through the same pressure reducing valve that is used when the primary steering pump provides the flow of pilot oil. The pressure reducing valve limits the pressure of the pilot oil to 1650 ± 150 kPa (240 ± 20 psi).

Illustration 1	g00118072
(1) Steering frame lock

Note: Before you perform this test, release any hydraulic pressure that may be in the steering system. Also, make sure that steering frame lock (1) is installed, as shown.

Reference: For the correct procedure for machine preparation, refer to Testing and Adjusting, "System Pressure - Release".

Check the Pressure of the Steering Pilot Pump

Show/hide table

Illustration 2	g02612477
Left side view (2) Steering pump (3) Steering pilot pump (4) Pilot oil filter

Show/hide table

Illustration 3	g06222257
Detail B (5) Steering pilot relief valve (6) Steering pilot check valve from pilot pump (7) Check valve for steering pilot oil cooler bypass (A) Pressure port for the pilot circuit

1. Open the access doors behind the cab. The components in the illustrations are on the left inner frame of the machine.
   Show/hide table

   Illustration 4	g06222263
   (Typical Example) Standard Location

   Show/hide table

   Illustration 5	g06222266
   (Typical Example) Remote Location (If Equipped)

2. Install a 0 to 3400 kPa (0 to 500 psi) pressure gauge on pressure port "PILOT-S" on the diagnostic plate. Make sure that the hydraulic tank filler cap is tight.

3. Start the engine. Allow the oil to reach normal operating temperature. Check the reading on the pressure gauge. With the machine at low idle, the correct pilot oil pressure should be 2400 ± 150 kPa (350 ± 20 psi) at 35 L/min (9 US gpm) and 49 °C (120 °F).

4. Stop the engine. Release all pressure in the steering system and in the braking system.

5. If the pressure reading is within the specification, remove the pressure gauge and proceed to "Adjusting Pilot Pressure of the Primary Steering Pump".

   If the pressure reading was not within the specification, proceed to Step 6.

   Show/hide table

   Illustration 6	g06222274
   Steering pilot relief valve (5) Steering pilot relief valve (8) Locknut (9) Adjustment screw

6. Locate steering pilot relief valve (5). Loosen locknut (8) and turn adjustment screw (9), as required. Turning adjustment screw (9) clockwise increases pilot oil pressure. Turning adjustment screw (9) counterclockwise decreases pilot oil pressure. One turn of adjustment screw (9) changes the pilot oil pressure by approximately 1895 kPa (275 psi).

7. Hold adjustment screw (9) in place and tighten locknut (8) to a torque of 10 N·m (90 lb in).

8. Start the engine. Allow the oil to reach normal operating temperature. Check the reading on the pressure gauge. With the engine at low idle, the correct pilot oil pressure should equal 2400 ± 150 kPa (350 ± 20 psi).

9. If the pilot oil pressure is not within the specification, repeat Steps 6 through 8.

   If the pilot oil pressure cannot be adjusted to the specification, install a new steering pilot relief valve. If you install a new steering pilot relief valve, make sure that you check the pilot oil pressure again.

   Note: If the pilot oil pressure is not within the specification after installation of a new steering pilot relief valve, check the condition of the oil filter. Replace the oil filter if the oil filter is contaminated with debris. Check the oil filter bypass valve. The oil filter bypass valve should not open until a pressure of 172 kPa (25 psi) is reached. If the oil filter and the oil filter bypass valve pass inspection, the steering pilot pump may be worn or damaged. Replace these components, as needed.

10. When the pressure reading is within the specification, stop the engine. Release all pressure in the steering system and in the braking system.

11. Remove the pressure gauge. Perform the second procedure "Adjusting Pilot Pressure of the Primary Steering Pump".

Adjusting Pilot Pressure of the Primary Steering Pump

Show/hide table

Illustration 7	g01458186
(10) Fitting

1. Disconnect fitting (10) on the steering control valve. Install a tee between the steering control valve and fitting (10).

2. Connect fitting (10) to the tee. Install a 0 to 3400 kPa (0 to 500 psi) pressure gauge on the unused tee fitting.
   Show/hide table

   Illustration 8	g06222274
   Steering pilot relief valve (5) Steering pilot relief valve (8) Locknut (9) Adjustment screw

3. Loosen locknut (8) on steering pilot relief valve (5). Turn adjustment screw (9) counterclockwise by one full turn. This will reduce the pilot oil pressure by approximately 1895 kPa (275 psi).

   Note: This adjustment will cause the pilot oil pressure of the steering pilot relief valve to be lower than the pressure of the steering pressure reducing valve. This allows the primary steering pump to supply the pilot oil for the steering system. The oil from the steering pilot pump then flows back to the hydraulic oil tank.

4. Hold adjustment screw (9) in place and tighten locknut (8) to a torque of 13 ± 1.7 N·m (115 ± 15 lb in).

5. Make sure that the hydraulic tank filler cap is tight. Start the engine. Allow the oil temperature to reach normal operating temperature.

6. While the engine is running at low idle, look at the pressure gauge. The reading on the pressure gauge should be 1650 ± 150 kPa (240 ± 20 psi).

7. If the pressure is within the specification, stop the engine. Release all pressure in the steering system and in the braking system and proceed to Step 12.

   If the pressure was not within the specification, leave the pressure gauge connected and proceed to Step 8.

   Show/hide table

   Illustration 9	g01458191
   Location of pressure reducing valve (11) Pressure reducing valve

   Show/hide table

   Illustration 10	g06222276
   Pressure reducing valve (11) Pressure reducing valve (12) Locknut (13) Adjustment screw

8. Loosen locknut (12) on pressure reducing valve (11). Turn adjustment screw (13), as required. Turning adjustment screw (13) clockwise increases pilot oil pressure. Turning adjustment screw (13) counterclockwise decreases pilot oil pressure. One turn of adjustment screw (13) changes the pilot oil pressure by approximately 500 kPa (72 psi).

9. Hold adjustment screw (13) in place and tighten locknut (12) to a torque of 13 ± 2 N·m (10 ± 2 lb ft).

10. Start the engine. Allow the oil to reach normal operating temperature. Check the reading on the pressure gauge. With the engine at low idle, the correct pilot oil pressure should be 1650 ± 150 kPa (240 ± 20 psi).

11. If the pilot oil pressure is not within the specification, stop the engine and release the pressure in the steering system and in the braking system. Repeat Steps 8 through 10 until the pilot oil pressure is within the specification.

    If the pilot pressure cannot be adjusted to the specification, install a new pressure reducing valve (11). If you install a new pressure reducing valve, make sure that you check the pilot oil pressure again.

12. Stop the engine.

13. Release the pressure in the steering system and in the braking system.

14. Loosen locknut (8) on steering pilot relief valve (5). Turn adjustment screw (9) clockwise by one full turn. This will increase the pilot oil pressure by approximately 1895 kPa (275 psi). This should set the steering pilot relief valve back to the correct pressure setting of 2400 ± 150 kPa (350 ± 20 psi).

15. Hold adjustment screw (9) in place and tighten locknut (8) to a torque of 10 N·m (89 lb in).

16. Remove the pressure gauge.