System pressure- -release
SMCS – 4000-553-PX; 4350-553-PX; 5050-553-PX; 6700-553-PX
Steps to release the pressure
Before repairing the hydraulic circuit, the hydraulic pressure in the hydraulic circuit must be released. The pressure of this hydraulic circuit shall be released before disconnecting or removing any hydraulic lines from the following hydraulic circuit.
Arm hydraulic loop
Bucket bar hydraulic loop
Bucket hydraulic loop
Turn the hydraulic circuit
Drive the hydraulic circuit
Attachment Hydraulic circuit (if provided)
Pilot hydraulic circuit
Reflow hydraulic circuit
Note: Refer to the Disassembly and Assembly manual for additional information on the specific hydraulic circuit components.
Hydraulic pressure release for the multiple hydraulic circuits
The pressure of rolling hot oil or hydraulic oil can cause harm to personnel.
After the engine stops, the hydraulic oil pressure will remain in the hydraulic system. Serious injury may occur without prior pressure release prior to repairs to the hydraulic system.
When removing the components or lines of the hydraulic system, ensure that all work tools are lowered to the ground
On, and the hydraulic oil temperature is already cold. Remove it only when the engine is stopped and the filler cap is cooled to freehand touch.
pay attention to
During inspection, maintenance, testing, adjustment and repair, the oil must be performed. Prepare a suitable container to collect fluid before opening any compartment or dismantling any stored parts.
For applicable tools and supplies for collecting and filling the fluid on Cat products, refer to special publications, NENG2500, “Agent Repair Tool Catalogue”.
Dispose of all liquids in accordance with local regulations and requirements.
Follow the following steps to release the hydraulic pressure from multiple hydraulic circuits of the main hydraulic system.
1. Park the machine on the horizontal ground.
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2. Fully withdraw the bucket rod cylinder connecting rod. Adjust the bucket position so that the bucket is parallel to the ground. Lower the boom until the bucket falls horizontally on the ground. See the illustration 1.
3. Turn off the engine.
4. Turn the engine start switch to the on position, but not starting the engine.
5. Place the hydraulic start control lever in the unlock position.
6. Move only the joystick or pedal of the repaired hydraulic loop to the full position. This will then release only the high pressure in this hydraulic loop. This will also release any pressure that may exist in the pilot hydraulic circuit.
Note: If the repaired hydraulic circuit needs to start the operating switch, start the corresponding operating switch in the hydraulic circuit.
7. Place the hydraulic start control lever in the locked position.
8. Start the engine.
9. Place the hydraulic start control lever in the unlock position. In this step, do not move any joystick or pedal away from the neutral position. In this step, do not turn in any switches.
10. Move the hydraulic start control lever back to the locking position.
11. Turn off the engine.
12. Repeat steps 4 to step 11 respectively for other hydraulic circuits that require maintenance.
13. After releasing the hydraulic pressure in each target hydraulic loop, place the hydraulic start lever in the locked position.
14. Turn the engine start switch to the off position.
15. Slowly release the filler plug on the hydraulic tank to release the pressure. The fill port plug shall remain loose for at least 45 seconds. This releases the pressure that may be present in the return hydraulic circuit.
16. Tighten the fill port plug on the hydraulic tank to achieve the specified torque.
17. The pressure in the multiple hydraulic circuits requiring repair is now released, and the lines and components can be disconnected or removed from these hydraulic circuits.
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