Fault Phenomenon: LiuGong 856 wheel loader when lifting the boom, steering completely fails or becomes extremely heavy.

Troubleshooting Process:
– Checked priority valve: flow priority valve spool stuck in non-priority position.
– Checked spring: priority valve spring broken.
– Checked oil quality: severely contaminated hydraulic fluid.
– Checked pressure: steering pump pressure normal but flow blocked.

Root Cause: The flow priority valve spool is stuck due to debris, causing all hydraulic oil to flow to the boom cylinder during high-load boom lift, leaving no flow for the steering system.

Required Parts: Clean or replace steering priority valve.