950G Series II Wheel Loader, 962G Series II Wheel Loader and IT62G Series II Integrated Toolcarrier Hydraulic System Caterpillar

Relief Valve (Main) - Test and Adjust

Usage:

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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, 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.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine.
To prevent personal injury or death, perform the following:
Park the machine on a smooth, level surface.
Lower the work tool to the ground and engage the parking brake.
Stop the engine and remove the key.

Block the wheels and install the steering frame lock.

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NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates.

Note: The method that is recommended for testing and adjusting a relief valve is removing the relief valve from the machine and testing and adjusting the valve on a test bench.

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Table 1
Required Tools
Part Number	Description	Qty
1U-5481	Pressure Gauge Group ⁽¹⁾	1
1U-5482	Pressure Adapter Group	1

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^( 1 )

The 198-4240 Digital Pressure Indicator is also available.

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Illustration 1	g00833859
Main Control Valve (Two Function) (1) Main relief valve.

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Illustration 2	g00833856
Main Control Valve (Three Function) (1) Main relief valve.

Machine Preparation For Troubleshooting

Park the machine on a smooth, level surface. Park the machine away from working machines and personnel. Lower the work tools to the ground.

Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.

Engage the parking brake.

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Illustration 3	g00914095

Place the steering frame lock in the LOCKED position.
Reference: For more information about preparing the machine for troubleshooting, refer to the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.

Testing The Main Relief Valve

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Illustration 4	g00833877
(2) Pressure tap for the main hydraulics

Connect 1U-5481 Pressure Gauge Group and 1U-5482 Pressure Adapter Group to pressure tap (2). The pressure tap for the main control valve is located at the articulation hitch on the rear frame.

Start the engine.

Run the engine at high idle. Operate the control levers and move all the cylinders in order to increase the temperature of the hydraulic oil to normal operating temperature. Run the engine at low idle.

Raise the lift arms to the maximum height.

Position the lift lever in the full RAISE position. Increase the engine speed to high idle.

Hold the lift control lever in the full RAISE position. Observe the pressure gauge.
Note: Do not keep the lift control lever in the full RAISE position for more than five seconds.
- On a standard machine, the pressure setting of main relief valve (1) should be approximately 20700 ± 340 kPa (3000 ± 50 psi).
- On a logging machine, the pressure setting of main relief valve (1) should be approximately 20700 ± 340 kPa (3000 ± 50 psi).
Note: If the pressure setting of the main relief valve is not adjusted correctly, it will be necessary to adjust the main relief valve.

Run the engine at low idle. Lower the lift arms to the ground. Turn the key start switch to the OFF position. Proceed to the Section "Adjusting The Main Relief Valve".

If the main relief valve is adjusted correctly, ensure that the work tool is on the ground. Remove the test equipment.

Place the steering frame lock to the STORE position.

Adjusting The Main Relief Valve

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Illustration 5	g00298584
Loader Tower Access Panel Lift arms are raised for photographic purposes only.

Ensure that the work tool is on the ground. Ensure that the engine start switch is in the OFF position. Remove the loader tower access panel that is over the control valve in order to access the main relief valve.

Move the control levers through the full range of travel several times. This will relieve any pressure that may be present in the implement hydraulic system.

Push the plunger on the breaker relief valve in order to relieve the pressure in the hydraulic tank.
Reference: For more information about releasing the pressure in the hydraulic system, refer to the Service Manual module Testing and Adjusting, "System Pressure - Release" for the machine that is being serviced.
Reference: Refer to Illustration 1 or Illustration 2 for the location of the main relief valve.
1. Ensure that the work tool is on the ground.
1. Loosen locking nut (3) and turn adjusting screw (4) clockwise in order to increase the relief valve setting. Turn adjusting screw (4) counterclockwise in order to decrease the relief valve setting.
1. After adjusting screw (4) is turned for an adjustment, tighten locknut (3) to a torque of 50 ± 7 N·m (37 ± 5 lb ft).
1. Repeat Step 2 through Step 6 of Section "Testing The Main Relief Valve" in order to verify that the pressure setting for the main relief valve is correct.