Fault Phenomenon: Caterpillar D9T dozer rear ripper cannot lift large rocks, action sluggish.

Troubleshooting Process:
– Checked system pressure: main pump output pressure insufficient.
– Checked cylinder: ripper cylinder internal leakage.
– Checked relief valve: main relief valve setting too low or stuck.
– Checked filter: suction filter clogged.

Root Cause: The main system relief valve spool is stuck partially open, preventing the system pressure from reaching the rated value.

Required Parts: Clean or replace main relief valve assembly.