Fault Phenomenon: Caterpillar D8T dozer during operation, after the blade is lifted, it slowly sinks automatically, unable to maintain height.

Troubleshooting Process:
– Checked cylinder: lift cylinder piston seals worn.
– Checked hydraulic lock: control valve internal leakage.
– Checked lines: no external leakage.
– Checked oil temperature: normal.

Root Cause: The blade lift cylinder piston seals are worn and failed, allowing high-pressure oil to leak into the low-pressure chamber (internal leakage).

Required Parts: Lift cylinder seal repair kit.