320B, 320B L,320B LN, 320B N, & 320B S EXCAVATORS MACHINE SY Caterpillar

NOTE: The slow return check valve is mounted to the main control valve.

Fluid Spillage Containment

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

1. Start the machine, and fully extend the stick and the bucket. Lower the stick and the bucket to the ground.

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At operating temperature, the hydraulic oil tank is hot and under pressure. Hot oil can cause burns. To prevent possible personal injury, release the pressure in all of the implement hydraulic circuits (the boom, the stick and the bucket) before any of the hydraulic lines or any of the components are disconnected or removed.

2. Release the pressure in all of the implement hydraulic circuits (the boom, the stick and the bucket) before any of the hydraulic lines or any of the components are disconnected or removed. Release the pressure as follows:

a. Shut off the engine and place key in the "ON" position. Put the hydraulic activation control lever in the "UNLOCK" position.

b. Move the control levers for the boom, the stick and the swing to all full stroke positions. This will release any pressure that might be present in the pilot system.

c. Return the key to "OFF" position.

d. Slowly loosen the fill plug on the hydraulic tank and release the pressure.

e. Tighten the fill plug on the hydraulic tank. Tighten the fill plug to a torque of 68 ± 7 N*m (50 ± 5 lb ft).

f. The pressure in the hydraulic system has been released and the hydraulic lines and the components can be removed.

3. Drain the oil from the hydraulic oil tank in a suitable container for storage or disposal. The capacity of the hydraulic oil tank is 130 liters (34 U.S. gal).

4. Remove four bolts (1), the washers and cover plate (2) from above the main control valve.

5. Oil will drain from the hose assemblies and pipe assemblies that are connected to the slow return check valve. Place a drain pan under the slow return check valve to contain the drain oil.

6. Disconnect hose assembly (3) from the slow return check valve. Put a plug in the end of the hose assembly to prevent oil loss and to keep contaminants out of the hydraulic system.

7. Remove six bolts (7) and the washers. Disconnect pipe assembly (4) from the slow return check valve and the cooler bypass check valve. Remove the pipe assembly from the machine.

8. Remove four bolts (5) and washers that hold slow return check valve (7) to the main control valve. Remove the slow return check valve from the machine. Remove the O-ring seal from the body of the slow return check valve.

NOTE: The following steps are for the installation of the slow return check valve.

9. Check the condition of the O-ring seals used between the slow return check valve, in pipe assembly (4) and in hose assembly (3). If the O-ring seals are worn or damaged, use new parts for replacement.

10. Install slow return check valve (6) in the reverse order of the removal steps.

NOTE: Refer to the topic "Lubricant Viscosities and Refill Capacities" in the "Operation & Maintenance Manual" for the proper filling procedure and the proper levels for the hydraulic oil system.

11. Fill the hydraulic oil tank with oil to the correct level.