How to relieve hydraulic pressure in the hydraulic circuit of 312D2 and 313D2 excavators
Steps to relieve pressure:
Before servicing a hydraulic circuit, you must relieve the hydraulic pressure in that circuit. Before disconnecting or removing any hydraulic lines from the following hydraulic circuits, relieve the pressure in that circuit.
• Boom hydraulic circuit
• Stick hydraulic circuit
• Bucket hydraulic circuit
• Swing hydraulic circuit
• Travel hydraulic circuit
• Attachment hydraulic circuit (if equipped)
• Pilot hydraulic circuit
• Return hydraulic circuit
Hydraulic pressure relief for multiple hydraulic circuits
WARNING: Hot oil or hydraulic oil pressure can cause personal injury.
After the engine is stopped, hydraulic oil pressure remains in the hydraulic system. Serious injury could result if pressure is not relieved before servicing the hydraulic system. Before removing hydraulic system components or lines, make sure all work tools are lowered to the ground and the hydraulic oil is cold. Remove the filler cap only when the engine is stopped and the filler cap is cool enough to touch with your bare hands.
NOTICE
During inspection, maintenance, testing, adjustments, and repairs of the product, care must be taken to ensure that any fluids that are drained are contained. Before opening any compartment or disassembling any component that contains fluids, have a suitable container ready to collect the fluids.
Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for appropriate tools and supplies for collecting and containing fluids on Cat products.
Dispose of all fluids in accordance with local regulations and requirements
Perform the following steps to relieve hydraulic pressure from multiple hydraulic circuits of the main hydraulic system.
1. Park the machine on level surface. CAT Caterpillar ET 3 Diagnostic Adapter 317-7485/478-0235 Diagnostic Tool-high quality
2. Fully retract the boom cylinder rod. Adjust the bucket position so that it is parallel to the ground. Lower the boom until the bucket is level with the ground. See Illustration 1.
3. Shut down the engine.
4. Turn the engine start switch to the on position, but do not start the engine.
5. Return the hydraulic start control lever to the unlocked position.
6. Move the control handle or pedal to the full position for only the hydraulic circuit that needs service. This will relieve high pressure only in that circuit. This will also relieve any pressure that may be present in the pilot hydraulic circuit.
Note: If the hydraulic circuit that needs service requires the activation of an operating switch, activate the appropriate operating switch on the hydraulic circuit.
7. Return the hydraulic start control lever to the locked position.
8. Start the engine.
9. Return the hydraulic start control lever to the unlocked position. Do not move any control handle or pedal from the neutral position during this step. Do not activate any switches during this step.
10. Return the hydraulic start control lever to the locked position.
11. Shut down the engine.
12. Repeat steps 4 through 11 for each of the other hydraulic circuits that need service.
13. After relieving hydraulic pressure from each target hydraulic circuit, place the hydraulic start lever in the locked position.
14. Turn the engine start switch to the OFF position.
15. Slowly loosen the filler plug on the hydraulic tank to release pressure. The filler plug should remain loosened for at least 45 seconds.
This will release any pressure that may be present in the return hydraulic circuit.
16. Tighten the filler plug on the hydraulic tank to the specified torque.
17. Pressure is now relieved from the multiple hydraulic circuits that require service and lines and components can be disconnected or removed from these hydraulic circuits.
