Yanmar 4TNV98 Emits Blue Smoke at Idle
Fault Codes & Symptoms
Blue smoke from exhaust at idle Related symptoms: - Increased oil consumption - Oil residue in intake piping Engine smokes excessively at idle. The smoke is blue. It seems worse after the machine has been idling for a long time.
Confirmed cause: Failed turbocharger compressor-side oil seal. Repair performed: The turbocharger was removed and replaced with a new unit. The charge air cooler and all associated intake piping were thoroughly cleaned of all residual oil to prevent runaway on restart. Verification: The engine was started and allowed to run at low idle for an extended period. No further blue smoke was observed from the exhaust. The engine was then tested under load and performed normally. Technician notes: - The symptom being worse at idle is a classic sign of a turbo oil seal leak. At low idle, low boost pressure in the compressor housing can be insufficient to keep oil from being drawn past a worn seal. - Always clean the charge air cooler and intake tract after a turbo failure. Oil accumulation in the intake can be ingested by the engine, leading to an over-speed or runaway condition. - Verify the oil supply and drain lines to the turbo are clear and not restricted before installing the new turbocharger.