Fault Phenomenon: LiuGong HBT80A exhaust brake functions normally when cold. During a long downhill descent (operating temperature), the exhaust brake fails, vehicle speed becomes uncontrollable, and eventually becomes dangerous.

Troubleshooting Process:
– Checked exhaust brake switch: switch function normal.
– Checked air solenoid valve: valve operates freely.
– Checked butterfly valve mechanical structure: butterfly valve not stuck.
– Measured butterfly valve cylinder pressure at operating temperature: found insufficient pressure.

Root Cause: The exhaust brake butterfly valve shaft deforms due to heat, causing it to stick and preventing closure.

Required Parts: Exhaust brake butterfly valve assembly.