Direct answer
If boom behavior changes with arm position or combined operation, document the exact pattern before assigning a pump or valve fault. Confirm that the machine plate identifies a PC360-8 and retain its complete serial number. This page does not prescribe a pressure adjustment.
Scope and safety
This is a symptom-recording and service-handoff guide, not a procedure for testing or adjusting the machine. Follow the exact machine manual and displayed safety instructions. Keep clear of moving equipment and suspected pressurized leaks. Shutdown alone may not remove stored pressure; hydraulic work and attachment support require the correct procedure and qualified personnel.
Record position and function separately
Describe the arm position when the complaint occurred, whether boom raising alone differed from combined operation, and whether an attachment was fitted. Use past observations; do not reproduce an unstable lift or overload condition.
Keep additional symptoms visible
If breaker performance was also weak, record it as a separate symptom with the breaker identity and operating mode. Do not assume that both symptoms prove the same failed valve.
Use the actual hydraulic diagram
Ask the technician to identify the relevant control circuit on the matching schematic. Terms such as priority control, pump power control and load sensing should not be used interchangeably. Request documented test findings before ordering a valve, regulator or pump.
Service handoff record
| Record | Information to supply |
|---|---|
| Identification | Full machine model and serial; engine or attachment identity where relevant. |
| Complaint | The affected function, direction, timing and original screen message. |
| History | Recent service, changed parts and existing test reports; mark missing information as unknown. |
| Diagnosis | Technician’s confirmed component, applicable manual reference and repair scope. |
Frequently asked questions
Does normal combined operation prove the pump is good?
It is useful evidence, but it is not a complete pump assessment. The test procedure and operating conditions matter.
Can I reset the main relief using a web value?
No setting is provided here. Adjustment requires the correct machine documentation and qualified service.
Sources and scope of evidence
- Komatsu parts and machine-specific manual access — manufacturer documentation or support access; obtain the reference for your exact machine.
- Caterpillar hydraulic hose inspection and pressure safety — general hydraulic inspection and stored-pressure safety.
These public sources provide documentation/support routes and general safety context. They do not verify a model-specific fault-code definition, pressure setting or repair case. This guide therefore supplies no such specifications. Source links checked 14 September 2026.
Related guides
- Excavator Hydraulic Pump Failure Symptoms and Next Checks
- How to Verify a Superseded or Replacement Part Number
- How to Check Parts Fitment Before an International Order
Parts identification after diagnosis
Danch Machinery supplies genuine parts. Send the confirmed part number, machine serial number and clear identification photographs for an availability and fitment inquiry. A symptom description does not establish fitment or current stock.
Request a parts identification check
About this guide
Published by Danch Machinery as general parts-identification and service-planning information. It is not a signed technical inspection or a machine-specific repair approval. Refer to the sources and scope stated in the article; confirm service procedures and fitment with the current manufacturer documentation for the exact machine.
Machine configurations and service requirements can differ by model, serial number and market. Confirm procedures and fitment with the current manufacturer documentation for your exact machine.
