330,330 L & 330 LN EXCAVATORS MACHINE SYSTEMS Caterpillar

NOTE: The pilot relief valve is installed in the pilot manifold which is located behind the right rear access door.

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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. Remove pilot relief valve (1) from the pilot manifold as follows:

a. Remove cartridge (8), spring (7), spool (3) and poppet (2) from the pilot manifold.

b. Remove O-ring seal (5) and plug (4) from the cartridge.

c. Remove the O-ring seal and back-up ring from the plug.

d. Remove nut (9) and screw (6) from the cartridge.

NOTE: The following steps are for the installation of the pilot relief valve.

3. Be sure all parts of the pilot relief valve are clean and free of dirt and debris. Put clean hydraulic oil on the components prior to installation.

4. Install the pilot relief valve as follows:

a. Temporarily install nut (9) and screw (6) in the cartridge. Check the condition of O-ring seal (5). If the seal is worn or damaged, use new parts for replacement. Install O-ring seal (5) on the cartridge.

b. Check the condition of the back-up ring and the O-ring seal for plug (4). If the ring and seal are worn or damaged, use new parts for replacement. Install the back-up ring and the O-ring seal on plug (4). Install plug (4) in the cartridge.

c. Install spool (3) in poppet (2). Install spring (7) and poppet (2) in the cartridge.

5. Install pilot relief valve (1) in the pilot manifold. Tighten the cartridge (8) to a torque of 80 ± 8 N·m (60 ± 6 lb ft).

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

7. Adjust the pilot relief valve pressure. See the "Testing & Adjusting" Module for the correct adjustment procedure.