M318 Excavator Hydraulic System Caterpillar

1. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release".

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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.

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Illustration 1	g00294248
The pressure tap is located in the battery compartment. (1) Main pump pressure

2. Connect a 60000 kPa (8600 psi) pressure gauge to pressure tap (1) .

3. Start the engine.

4. Lower the left console.

5. Place the engine speed dial at the HIGH IDLE position.

6. Turn the signal limiter valve inward until the valve contacts the stop. Refer to Testing and Adjusting, "Relief Valve (Signal Limiter) - Test and Adjust" or Testing and Adjusting, "Relief Valve (Signal Limiter Heavy Lift) - Test and Adjust".

7. Increase the main relief valve pressure to a maximum of 42500 kPa (6165 psi). Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".

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Illustration 2	g00610229
Main control valve Stick relief valve (head end)

8. Increase the stick relief valve (head end) to a maximum of 36000 to 38000 kPa (5220 to 5510 psi) for machines without the heavy lift option. Increase the stick relief valve (head end) to a maximum of 40000 to 42000 kPa (5800 to 6090 psi) for machines with the heavy lift option.

Test

1. Move the joystick to the full STICK OUT position until the stick cylinder is fully retracted.

2. While the joystick is in the full STICK OUT position, check the pressure at pressure tap (1). This is the pressure setting of the stick lowering control valve. Refer to Testing and Adjusting, "Specifications".

Adjust

1. If the stick lowering control pressure is incorrect, turn the adjustment screw in order to adjust the stick lowering control valve.

2. Adjust the stick relief valve (head end) to the original setting. Refer to Testing and Adjusting, "Main Control Valve - Adjust (Implement Control Spools)".

3. Adjust the main relief valve to the original setting. Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".

4. Adjust the signal limiter valve to the original setting. Refer to Testing and Adjusting, "Relief Valve (Signal Limiter) - Test and Adjust" or Testing and Adjusting, "Relief Valve (Signal Limiter Heavy Lift) - Test and Adjust".