Turbos: Tackling oil contamination

The majority of turbo failures are caused by problems that have nothing to do with the turbo itself. That is why it is important to determine why it failed, and fix it, before simply fitting a new one, otherwise the replacement unit could fail too. Here we discuss one of the most common causes of turbo failure: oil contamination.

WHAT IS OIL CONTAMINATION?

With tolerances measured in microns, and operating speeds of over 300,000 revs per minute, turbochargers need a regular supply of good quality and clean oil to keep them churning over. Unfortunately, fuel, dirt, combustion residues, water, and other contaminants can easily contaminate the oil, and even the smallest particles can result in serious wear to crucial components, and potentially serious damage to the turbocharger, and even the engine.

WHAT CAUSES IT?

There are a myriad of possible causes of oil contamination. They include:

• Filter problems such as blockage, damage, or poor quality components

• Issues with the filter bypass valve

• Carbon build-up in engine or oil supply lines

• Poor quality engine oil due to either overly high temperatures and/or overdue servicing and maintenance

• Engine leaks that cause water, coolant or fuel to contaminate the oil

• Poor servicing techniques or engine wear and tear which introduce debris or dirt into the engine

WHAT ARE THE SYMPTOMS?

Performance issues and component wear could present themselves via:

• Warning lights (i.e. check engine light) and loss in vehicle power — limp home mode

• Scoring/grooves to either journal bearing, journal bearing diameters of shaft, wheel, and thrust components

• Larger particles can cause internal damage to the shaft and bearing

• Wear to oil flinger/flinger grooves which can lead to oil leaks

• Piston ring wear and tear that causes oil to enter the turbine side and increased oil usage

• Turbine and/or compressor wheel coming into contact with the housing bore due to excessive play in the shaft from worn bushings/bearings

• Blocked internal oil galleries restricting oil flow

• Smell of fuel in the oil

How To Fix It

Sure, preventing oil contamination via quality parts, servicing, and following manufacturer’s recommendations is better than having to fix it. However, if problems occur here is a quick guide that can help:

• Do an oil system flush and refill following manufacturer guidelines and using quality parts

• Clean the oil supply and return system (you might need to remove the sump, oil pump, and internal oil lines) — replace parts as needed

• When replacing the turbo, perform an oil pressure test to identify issues in the oil supply and return system.

This may add additional expense to your customer’s bill, but it is far more cost and timeeffective than having to fit another turbo, and potentially an engine, when they return with the same issue soon after.