Komatsu PC220-L5 Oil in Turbo and Exhaust Problem

[MikePhua]

Engine Model and Machine Background
The Komatsu PC220-L5 is a hydraulic excavator powered by the Komatsu S6D95L engine. This model has been used for years in demanding environments, favored for its balance of digging power, reliability and parts availability. The S6D95L is a six-cylinder diesel with strong torque output, built for durability. Over its production span, PC220 series machines have been widely deployed in road building, large-site excavations, and infrastructure works.
Symptom Description and Terminology

• Blue Smoke at Idle: Blue smoke from the exhaust typically indicates that oil is burning with the fuel-air mixture, especially when the engine is cold or idling.
  
• Oil Leak through Turbo: Oil entering the turbocharger and being expelled via the exhaust path. This means the turbo is receiving engine oil via either the oil feed or by excessive crankcase pressure pushing oil past seals.
  
• Blow-by and Crankcase Pressure: Blow-by is when combustion gases escape past piston rings into the crankcase, raising pressure. The crankcase vent (or PCV, positive crankcase ventilation) should relieve this pressure.
  

Probable Causes

• Clogged Oil Drain from Turbo: If the oil drain line from the turbo back to the oil pan is blocked or severely restricted, oil cannot properly flow back. This causes oil to pool in the turbo housing and get pushed into the exhaust.
  
• Blocked Crankcase/Ventilation Path: If the crankcase ventilation is blocked (e.g. via the valve cover ventilation line), pressure builds up, forcing oil past seals and into the turbo/exhaust.
  
• Worn Piston Rings or Cylinder Walls: Excessive clearance or wear allows oil to bypass the rings and enter the combustion chamber. This increases oil consumption and contributes to smoke.
  
• Failure of Turbo Seals or Bearings: Even with a new turbo installed, if seals are compromised or bearings worn, oil may leak internally.
  

Troubleshooting Steps

• Check the oil return line from turbo to oil pan; remove any blockage and verify oil flows freely.
  
• Inspect and clean crankcase ventilation lines, valve cover breather, and any PCV type systems to ensure they are not plugged.
  
• Remove and inspect piston rings, cylinder liners if blow-by seems high. Use compression or leak-down tests.
  
• Examine the turbo seals and bearings; even replacement turbos can be poorly performing if installation or related oil supply/drain/ventilation is suboptimal.
  

Resolution Case
In one reported instance, after replacing the turbo, the problem persisted. The owner discovered that the oil return was partially blocked (not completely plugged), and the ventilation path from valve cover to crankcase was fully blocked. After cleaning the return line and clearing the ventilation passage, the excavator ran with substantially less smoke, especially at idle, and oil leaking into the exhaust ceased.
Preventive Measures and Recommendations

• Maintain regular inspection intervals for ventilation paths and oil return lines—every 250-500 operating hours or sooner under dusty or wet conditions.
  
• Use high quality oil and change it per manufacturer schedule; oil viscosity and cleanliness affect seal performance.
  
• Monitor exhaust smoke color regularly: blue means oil burning, black means fuel-rich, white means water or coolant. Early detection prevents major damage.
  
• Ensure turbo installation is correct: gaskets, drain line slope, sealing surfaces clean, bolts torqued correctly.
  

Why This Matters to Operators
Smoke, oil leaks, and engine inefficiencies reduce equipment uptime, increase fuel consumption and oil costs, and may lead to overheating or turbo failure. In regions with emission regulations, excessive smoke can lead to compliance issues. A PC220-L5 that is maintained well in its oil and vent systems can serve many thousands of hours, whereas neglect can drastically shorten service life.