Fault Phenomenon: Lonking 855 wheel loader after turning and returning the steering wheel to center, the wheels slowly drift automatically.

Troubleshooting Process:
– Checked cylinder: steering cylinder piston seals worn, internal leakage.
– Checked bi-directional cushion valve: spool internal leakage or stuck.
– Checked steering unit: full hydraulic steering unit internal leakage.
– Checked lines: no external leakage.

Root Cause: The bi-directional cushion valve (compensation valve) spool inside the steering cylinder is stuck by debris, unable to seal the high-pressure oil, causing cross-communication between cylinder chambers.

Required Parts: Clean or replace steering cylinder bi-directional cushion valve assembly.