Turbochargers can operate at speeds of over 200 000 RPM, driven by exhaust gasses of over 950 °C. The lubricating oil provides a pressurised film of oil between all rotating components and the bearing surfaces. Oil drains from these surfaces into a non pressurized internal cavity for drainage back to the engine sump. Piston ring type seals use the positive pressure differential in the compressor and turbine housings to stop oil leakage from the turbocharger.
Causes of oil leaks into both compressor and turbine housings
Excessive oil pressures. A turbo is designed for an oil supply pressure of 4 bars and pressures in excess of this may cause oil seepage.
Damage to the turbochargers rotating assembly, especially broken turbine shafts.
A blocked engine breather systems causing sump compression that inhibits oil drainage.
Frequent “hot shut downs” cause a build up of oil sludge, blocking oil drainage from the turbo charger.
Excessively worn bearings.
High engine oil levels restricting oil drainage.
A blocked/restricted or bent oil drain pipe.
Causes of oil leaks into the compressor housing
A blocked or restricted air filter, pipe or hose can create a negative pressure differential which allows oil leakage past the oil seals.
Loss of boost pressure do to damaged/leaking pipes or intercooler can also allow oil leakage past the oil seal.
Extended periods of engine idling can cause oil seepage into the compressor housing.
Causes of oil leaks into the turbine housing
Leaks in the exhaust manifold/manifold fitting or turbo mounting causing a reduced pressure differential.
Leaks in the EGR system causing a reduced pressure differential.
Preventing turbocharger oil leaks
Check and correct all restrictions to oil drainage.
Ensure engine oil levels are correct.
Check and correct all leaks in the engine air intake and exhaust systems that can cause a reduced pressure differential between the housings and internal oil cavities.