Fault Phenomenon: Doosan D30S diesel forklift when going downhill, engage the exhaust brake, find no braking effect, vehicle speed uncontrollable.

Troubleshooting Process:
– Checked exhaust brake switch: switch indicator light on.
– Checked air solenoid valve: valve not actuating.
– Checked butterfly valve mechanical structure: butterfly valve stuck in open position.
– Checked air pressure: pressure normal.

Root Cause: The exhaust brake butterfly valve shaft is corroded and stuck, preventing closure of the exhaust passage.

Required Parts: Exhaust brake butterfly valve assembly.