A construction crew reported that a Doosan DX300LC-7 excavator emitted heavy blue smoke from the exhaust and consumed 5 liters of engine oil per day. The engine lacked power on hills.
The technician checked the "Radiator" and found oil residue in the coolant (mayonnaise-like sludge). He removed the "Cylinder Head Cover." The internal rocker arms were covered in thick, black sludge. He checked the "Crankcase Ventilation (CCV) Filter." The filter element was completely blocked with carbon.
He then performed a "Cylinder Compression Test." The #3 and #4 cylinders had low compression (18 bar vs. spec 28 bar). He removed the cylinder head. The "Piston Rings" on cylinders #3 and #4 were broken. The broken rings allowed combustion gas to bypass the piston (blow-by), pressurizing the crankcase.
The blocked CCV filter trapped this pressure inside the engine. The high pressure forced oil past the valve seals and into the intake manifold, causing the blue smoke. The broken rings caused the low power.
The repair involved replacing all piston rings and the cylinder liners. The CCV filter housing was cleaned. The cylinder head was pressure-tested and lapped. The radiator was chemically flushed. After reassembly, the blue smoke cleared, and the engine power was restored.
