424B Backhoe Loader Hydraulic and Steering System Caterpillar

Relief Valve (Loader) - Test and Adjust

Usage:

424B JRN

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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine.

To prevent possible injury, perform the procedure that follows before testing and adjusting the brake system.

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Escaping fluid under pressure, even a pinhole size 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.

Always use a board or cardboard when checking for a leak.

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Table 1
Required Tools
Part Number	Description	Quantity
8T-0860	Pressure Gauge	1
177-7862	Hose As	1
6V-4143	Quick Connect Coupler	2
5P-3413	Pipe Sealant	1

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Table 2
Specifications
Hydraulic Oil Temperature	65 ± 5 °C (149 ± 9 °F)
Engine RPM	1200 ± 100

The LS pressure tap is located on the pump controller for the pump discharge pressure. Access is gained from the bottom of the machine.

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Illustration 1	g03590097
(1) Loader valve (Two Bank) (2) LS Relief Valve (3) Locknut (4) Adjusting Screw

Install one 6V-4143 Quick Connect Coupler to each end of the 177-7860 Hose As.
Install one 8T-0860 Pressure Gauge with a range of 0 to 40000 kPa (0 to 5802 psi) to the hose. Install the hose to pump discharge pressure tap.
Engage the parking brake. Start the engine. Keep the machine in neutral.
Operate the hydraulics to the operating temperature range of 65 ± 5 °C (149 ± 9 °F).
Run the engine at 1200 RPM.
Raise the loader arms completely to the full RAISED position.
Note: Relief valve (2) is installed in the outlet manifold on all of the machines.
Note: There may be air in the signal network, if there is a hesitation before reaching the relief pressure. Purge the signal lines of the air.
If the pressure for the relief valve is correct, then go to Step 14. If the relief pressure is not correct, then the relief valve needs adjusting.
Stop the engine.
Remove the cap on relief valve (2).
Loosen locknut (3) on relief valve (2).
Turn the screw (4) clockwise in order to increase the pressure. Turn the screw (4) counterclockwise in order to decrease the pressure.
Tighten locknut (3) to a torque of 20 N·m (177 lb in).
Repeat Steps 5, 6, and 7. If the relief valve cannot be set correctly, repeat Steps 9, 10, 11, and 12.
Turn off the engine and remove the test equipment.