Turbocharger Failure Troubleshoot

Lack of Lubrication /
Contaminated Oil

The lubrication system plays an essential role in prolonging the life expectancy of a turbocharger by lubricating, cooling and cleaning the bearings. The shaft and bearings must soar on a constant, clean film of oil to prevent direct contact with each other, which will result in damage. Any lack of oil flow or foreign contaminant, i.e. dirt, sand or metal shavings in the oil will cause excess wear and/or scaring on the bearing surfaces. This wear will often increase the clearances between rotating components resulting in excess shaft motion. A large amount of shaft motion is harmful to the life of a turbocharger.

Common causes of lubrication failure:

• Low engine oil pressure / level
• Blocked oil supply / drain lines
• Inappropriate weight of oil
• Contaminated oil
• Quick start-up of turbocharger in cold temperature
• Hot shutdown of turbocharger - Engine is turned off at high rpm or temperature; instant oil flow loss results in overheating

External lack of lubrication often happens when anything exterior to the turbocharger is affecting the oil flow such as supply or drain lines and engine blow. All thrust and journal bearings and turbine shaft will show signs of heat discolouration as well as wear from the resulting shaft motion. The wear will appear smooth or "wiped" and should not have any significant scorings.

Meanwhile, internal lack of lubrication is visible when one or more (but not all) of the bearings show the above mentioned wear. This indicates that only one of the oil feed lines has been blocked from either contaminated oil or a manufacturers' defect. Contaminated oil, on the other hand, occurs when abrasive material such as dirt, sand, or metal shavings enters the oil passages. This is generally easy to notice as the bearings and connecting components will show abnormal grooves and scratches. This may also cause a lack of lubrication failure as noted above.

Foreign Object in Exhaust /
Compressor Wheel

Foreign objects such as screws, nuts, sand, metal power, broken air filters and other foreign objects entering the turbine or compressor will severely damage the rotating turbine or compressor wheels. Both wheels are precisely balanced to spin at extremely high operating speeds required by their application. If either wheel is damaged, the rotating assembly will no longer maintain its balanced position, which will result in severe shaft motion causing almost every component of the turbocharger to breakdown and fail.

More often than not, this particular damage is the easiest damage to recognise as the compressor or turbine wheel will often show severe damage without removing the housing. However, in some scenarios, this is a gradual erosion of the wheel from fine particles such as sand or dirt. In this case, the wheel will display small pits across the vanes or minor wear on the inducer tips. Although rare, this failure may also be caused by the compressor wheel lock nut loosening off and entering the compressor vanes. This failure originates from assembly if the lock nut was not tightened to the required torque setting.

High Exhaust Temperature

Excessive temperature in the exhaust system will cause the lubricating oil to "coke" in the bearing housing drain annulus at the turbine end. This causes oil leakage into the turbine housing. Coke and carbon deposits will be visible and eventually damage the back of the turbine wheel and cause abnormal wear on the thrust bearing. High exhaust temperatures can also erode and crack the turbine housing and/or bearing housing. Excessive heat discolouration of the turbine shaft is usually visible. The piston ring in the turbine side of the bearing housing will often appear relaxed if it has been submitted to these high temperatures.

High exhaust temperatures can originate from several operating conditions encompassing:

• Incorrect fuel ratio (high fuel setting)
• Insufficient air supply caused by a clogged air cleaner, etc.
• Leak in the intake manifold or piping
• Excessive exhaust restrictions
• Plugged in after cooler core

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