PLATE 5P4918 - Caterpillar

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 bolts (1) and sheet assembly (2) from the service platform area. 3. Disconnect wiring harness (6) from the proportional reducing valve.4. Disconnect hose assembly (3) from the proportional reducing valve. Put a plug in the end of the hose assembly to prevent oil loss and to keep dirt and debris out of the hydraulic system.5. Remove two socket head bolts (4) and proportional reducing valve (5) from the pilot manifold. Remove the two O-ring seals from the proportional reducing valve. Install the proportional reducing valve in the reverse order of removal.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.Disassemble & Assemble Proportional Reducing Valve
Start By:a. remove proportional reducing valve1. Make sure the outside of the proportional reducing valve is clean and free of dirt and debris prior to disassembly. 2. Remove two O-ring seals (1) from the proportional reducing valve.3. Remove two socket head bolts (2) and solenoid (3). 4. Remove O-ring seal (7), rod (4), spool (6) and spring (5) from valve body (8). Assemble the proportional reducing valve in the reverse order of disassembly. Prior to assembling the proportional reducing valve, make sure all parts are clean and free of dirt and debris. Put clean hydraulic oil on the internal parts of the valve. Also, check the condition of the O-ring seals. If the seals are worn or damaged, use new parts for replacement.End By:a. install proportional reducing valve