M313C, M315C, M316C, M318C and M322C Excavators and M318C and M322C Material Handlers Hydraulic System Caterpillar

This procedure is utilized to adjust the pressure setting for the primary line relief valve and the secondary line relief valve for the medium pressure function. The primary line relief valve limits the maximum pressure of the medium pressure function. The line relief valves limit the maximum line pressure, in addition to protecting the control valve from pressure spikes that are induced by external forces.

Table 1

Required Tools
Part Number	Part Description	Qty
8T-0859	Pressure Gauge (0 to 25,000 kPa (0 to 3,600 psi))	1
6V-3989	Fitting (TEST)	1
6V-4143	Quick Connect Coupler	2
6V-3014	Hose As	1

1. Prior to any adjustment, refer to the "Preparations" section in Testing and Adjusting, "Operational Checks".

Test and Adjust for the Secondary Line Relief Valve

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Illustration 1	g01256501
The remote pressure taps are located behind the left rear access door. (1) Pressure tap (Pilot, brake, auxiliary tool, and steering pump)

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Illustration 2	g01204468
Medium Pressure Control Valve (2) Primary line relief valve (3) Secondary line relief valve

1. Connect a 25000 kPa (3600 psi) pressure gauge to pressure tap (1) .

2. Start the engine.

3. Adjust the engine speed to HIGH IDLE by turning the engine speed dial to position 10.

4. To check the setting of secondary line relief valve (3) for the medium pressure function, you must apply an external pressure to the circuit. This is accomplished by using an external pump or by loading an adjustable ditch cleaning bucket by pressing one corner of the bucket to the ground in order to apply pressure to this circuit from outside.

5. Measure the opening point (pressure drop point) in the circuit on an external pressure tap.

6. Allowable secondary line relief valve pressure is 22000 kPa (3191 psi) maximum. Allowable pump pressure is 20000 kPa (2901 psi) maximum.

7. To adjust the pressure on the secondary line relief valve, loosen the locknut on secondary line relief valve (3). Turn the adjustment screw clockwise in order to increase the pressure setting. Turn the adjustment screw counterclockwise in order to decrease the pressure setting.

   Note: Always make the final pressure adjustment on the pressure rise.

8. When the adjustments are complete, tighten the locknut for the adjustment screw to the proper torque.

9. Once the secondary line relief valve is adjusted to the recommended setting, use the following procedure to adjust primary line relief valve (2) .

Test and Adjust for the Primary Line Relief Valve

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Illustration 3	g01256501
The remote pressure taps are located behind the left rear access door. (1) Pressure tap (Pilot, brake, auxiliary tool, and steering pump)

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Illustration 4	g01256502
Medium Pressure Control Valve (2) Primary line relief valve

1. Connect a 25000 kPa (3600 psi) pressure gauge to pressure tap (1) .

2. Operate the medium pressure function against the end position of the cylinders. Check the pressure at pressure tap (1). Refer to Testing and Adjusting, "Specifications" in this manual for the correct pressure setting.

3. While the medium pressure function is stalled, adjust the pressure setting of primary line relief valve (2). Loosen the locknut and turn the adjustment screw until the pressure at pressure tap (1) is set to the correct pressure. Turn the adjustment screw clockwise in order to increase the pressure. Turn the adjustment screw counterclockwise in order to decrease the pressure.

   Note: Set the pressure to a pressure that is less than the pressure that is recommended by the manufacturer of the tool by 1000 kPa (145 psi).

   Note: Always make the final pressure adjustment on the pressure rise.

4. When the adjustments are complete, tighten the locknut for the adjustment screw to the proper torque.