A little oil is normal
Crankcase gases are recycled back into the intake via the breather: a light oily film in the turbo hoses is therefore normal on an engine that has done some mileage. What is not normal is oil that drips, accumulates in the intercooler, or is accompanied by blue smoke.
Likely causes
- Blocked or kinked turbo oil return. Oil can no longer drain back to the sump and escapes past the turbo seals. This is a very common external cause.
- Excessive crankcase pressure: blocked breather, or a worn engine allowing blow-by gases to pass through.
- Clogged air filter: the resulting vacuum draws oil past the compressor-side seal.
- Worn turbo bearings and seals, with play in the shaft.
The risks
Oil that has built up in the intercooler can be suddenly drawn into the engine. On a diesel, a large quantity can cause a runaway. It also clogs the EGR valve and the diesel particulate filter.
What should you do?
Have the turbo shaft play checked with the engine cold, then have the oil return, the breather and the air filter inspected. If the turbo needs replacing, the fitting process should include a thorough clean of the intercooler and hoses, an oil change, and correction of the underlying cause. If it is the engine itself that is worn and pressurising the crankcase, a reconditioned bare engine with a warranty of up to 24 months solves the problem at source.
