330,330 L & 330 LN EXCAVATORS MACHINE SYSTEMS Caterpillar

NOTE: The slow return check valve is located next to the main control valve, on the left side. The hood has been removed from the machine and the cover assembly over the main control valve was removed for better photo illustration of the slow return check valve.

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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 the implement hydraulic circuits (boom, stick and bucket) before any hydraulic lines or components are disconnected or removed.

1. Release the pressure in the hydraulic system as follows:

a. Fully retract the rod in the stick cylinder.

b. Adjust the position of the bucket so it will be flat on the ground when the boom is lowered.

c. Lower the boom until the bucket is flat on the ground.

d. Shut off the engine, and put the hydraulic activation control lever in the "Lock" position.

e. Move the control levers for the boom, bucket, stick and swing through their full travel strokes. This will relieve any pressure that may be present in the pilot system.

f. Slowly loosen the air breather cap on the hydraulic oil tank to release the pressure.

g. Tighten the air breather cap on the hydraulic oil tank.

h. The pressure in the hydraulic system has now been released. Lines and components can now be removed.

2. Open the hood. Remove the access covers above the slow return check valve.

3. Remove the four socket head bolts from slow return check valve (1). Remove the slow return check valve from between the tube assembly and elbow.

4. Disassemble the slow return check valve as follows:

a. Remove the two setscrews and retainer (4) from the valve body.

b. Remove O-ring seal (3) from the retainer.

c. Remove spring (2) and valve (6) from the valve body (5).

NOTE: Assemble and install the slow return check valve in the reverse order of disassembly. Prior to assembling and installing the slow return check valve, check the condition of O-ring seal (3) and the O-ring seals used in the tube assembly and elbow for mounting the valve. If the seals are worn or damaged, use new parts for replacement.

5. Check the oil level in the hydraulic oil tank. Fill the hydraulic oil tank with oil to the correct level. See the Operation & Maintenance Manual for the correct filling procedure.