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Common VGT

Failure Modes

and

Troubleshooting

21

VG Electronic Actuator

§Electronic Actuator is a smart device• It can run own diagnosis and report

§ Turbo and actuator works as a team• Turbo functionality is constantly monitored and reported to the ECM

§Having an actuator fault code does not all ways mean the actuator or turbo is bad• Combination of the fault code and the time it triggered is important for proper

diagnosis

• Remember there are other components upstream and downstream affecting the operation of the turbocharger

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22

VG Actuator Common Failure Modes

§ Communication fault codes (Fault Code 2636)

• Wiring harness / Connector of the Engine / intermittent connection

• Coolant leaks / Fluid intrusion

• Customer Damage / Tampering

§ Sticking Codes (Fault Code 2387)

• Check the turbo shaft sector gear

§ Internal defects

• Actuator circuit issue

• Hardware issue

• Customer Damage / Tampering

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23

Fault Code 2636 (QuickServe Online)

§ Communication fault codes (Fault Code 2636)

• Wiring harness / Connector of the Engine / intermittent connection

• Coolant leaks / Fluid intrusion

• Customer Damage / Tampering

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24

Fault Code 2636 (QuickServe Online)VGT Actuator Driver Circuit - Abnormal Update Rate

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25

Fault Code 2636 (QuickServe Online) VGT Actuator Driver Circuit - Abnormal Update Rate

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26

Consequential DamageConsequential Damage Breakdown:

• Soot Build Up (Fault Code 2387)

• Regen Issues

• Over Fueling

• Injector Condition

• Shellac Build Up (Fault Code 2387)

• Hot Shutdowns

• Injector Condition

• Coolant or Oil in Exhaust (Fault Code 2387)

• Engine Condition

• EGR Cooler Failure

If possible, looking in the Turbine Housing Inlet might help you

identify why the turbo is sticking

• Compressor Side Oil Leak

• Restricted Intake Filter / Oil Drain

• Application Fault

• High Crankcase Pressure

• Boost Leaks

• Closed Crankcase Ventilation

• Operating Conditions (Higher risk at Cold Temperatures)

29

Compressor Wheel Foreign Object Damage (FOD)

§ Tools, rags and debris from previous failures can cause significant damage to impellers.

§ Smaller amounts of damage can accumulate from poor quality or poorly fitting inlet systems or inadequate air filters.

§ Noise, poor performance and out of balance bearing failures can follow.

§ Never continue to operate a turbocharger that is showing evidence of foreign object damage

§ Fault Code 2387 and Low performance codes

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30

Turbine Wheel Foreign Object Damage (FOD)

§ Foreign material from the engine (e.g. broken pistons, valves) or debris left behind during engine work can bend or break turbine vanes

§ Due to the damage to nozzle vanes the impacts on VGT can be more significant in terms of ability of the turbo to continue to function

§ Damage can lead to noise, loss of performance or bearing (imbalance) failures

§ Never continue to operate a turbocharger that is showing evidence of foreign object damage

§ Fault Code 2387 and Low performance codes

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31

Nozzle Vane Foreign Object Damage (FOD)

§ Small hard particles exiting the engine can cause progressive and accumulated damage to the VG nozzle ring vanes

§ This progressive damage erodes the nozzle ring vanes and can cause deflection of the vanes

§ The vanes then become bound or seized within the shroud plate resulting in a stuck VG mechanism

§ Never continue to operate a turbocharger that is showing evidence of foreign object damage

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33

Insufficient oil supply – oil delay

§ Journal bearings

• Polished and burnished on inner and outer diameters

• Possibly on end faces too

§ Thrust bearing

• Polished and worn on bearing surfaces

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Some possible causes:

• Restricted oil feed pipes• Low oil level in sump• Low oil pressure due to malfunctioning

systemOil pump failureOil filter blocked

• Long periods of non-use• Refitting a turbo without adequate

priming• Very cold weather causing oil to be very

viscous

34

Insufficient oil supply – Oil starvation§ Broken or restricted oil feed pipes

§ No or low oil in sump

§ Low oil pressure due to malfunctioning system

• Oil pump failure

• Oil filter blocked

§ Use of silicone sealants causing blockage

§ Shaft and wheel

• May show signs of dis-colouration caused by excessive heatdue to lack of oil

§ Journal bearing

• Discoloured and scored

§ Thrust Bearing

• Will show signs of discoloration

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36

Oil Contaminated with other fluid

§Oil contaminated with other engine fluids leads to different failure types

§Corrosion of the bearing material is caused by acid attack from the compounds produced by coolant as it is heated and oxidised in the oil

§ The acid attack, creates a pitted surface on the bearings that leads to bearing system damage

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38

Dirty oil

§ Effects of dirty oil :

• Shaft and wheel :

- Score marks and possible seizing

• Journal bearings :

- Score marks in internal and external diameters

• Bearing housing :

- Score marks and possible blocked oil feed holes

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39

Over heating§ Blocked air cleaner / excessive intake restriction

§ Infrequent oil change intervals causing oil breakdown in service

§ Carbonizing due to poor quality oil

§ Repeated “Hot Shut Downs”

§ Air and gas leaks

§ Faulty fuel pump or injectors

§ Non-approved turbine housing

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41

Incorrect re-installation / Dirty Air Intake

§ Compressor end oil leakage

• Collapsed inlet pipework

§ Turbine end oil leakage

• Blocked oil drain

• Incorrect oil drain gasket.

• Damaged oil drain hose or tube.

• High engine blow-by pressure - which can be due to the engine crankcase vent being blocked by damage, plugging or icing, or heavy wear in the power-cylinder or valve guides

§ Dusting / Compressor FOD

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42

Incorrect application for turbocharger / Modification

§ Using a turbo on a different application or modifying the turbo so that the operating conditions are away from the original intended application could cause unexpected early life failures:

• Examples:

- Using a truck turbo (cast impeller) for a bus application

- Using a cast impeller turbo rather replacing with the original MFS impeller turbo

- Modifying the turbo to run at higher turbo speeds i.e. changing wastegate pressure for more boost

- Using a turbo on engine not fuelled with diesel i.e. natural gas application

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