Cause of Failure

Lack of Lubrication or Oil Degradation

Causes:

  • Low engine oil levels
  • Obstructions in oil feed lines
  • Build up of burnt oil in center housing
  • Excessive Temperature
  • Inferior oil quality.

Symptoms:

  • Oil leakage
  • Noise
  • Loss of power
  • Excessive smoke
  • Excessive oil consumption

Consequences:

  • Excessive wear of journal bearings, thrust bearing, and thrust collar.
  • An imbalance causing excessive wear to rotating components.
  • Wear of sealing surfaces of back plate and thrust collar.
  • Piston ring failure or leakage.

Contaminated Oil

Causes:

  • Saturated oil filter
  • Recycled Oil
  • A rebuilt engine with impurities within the oil passages
  • Burnt oil from high temperatures
  • Residue from incomplete combustion

Symptoms:

  • Oil leakage
  • Noise
  • Loss of power
  • Excessive smoke
  • Excessive oil consumption

Consequences:

  • Scoring and wear of journal bearings
  • Scoring and wear of thrust bearing and thrust collar
  • Imbalance
  • Failed components

Foreign Body Ingestion

Causes:

  • Materials ingested into either the compressor, or turbine side of the turbo
  • Damage to the compressor side suggests an insufficient/dirty air filtration system, or a damaged air intake tubes.
  • Damage to the turbine suggests damage to the engine such as parts of the pistons, or valves.

Symptoms:

  • Loss of power
  • Noise
  • Excessive smoke

Consequences:

  • Damage to the wheels.
  • Imbalance to the rotating assembly.
  • Excessive wear to the rotating assembly.

Hot Shutdown

Causes:

  • Frequent turning off the engine at high speed.
  • Inferior oil quality.
  • High operating temperature.

Symptoms:

  • Oil leakage
  • Excessive smoke

Consequences:

  • Extensive deposits of carbon and shellac in the turbine end seal parts and bearing system.
  • In early stages of failure, bearing clearances are decreased by the deposits.
  • As the problem continues, the deposits break up, scoring and wearing the bearing bore, journal bearing, and shaft.

Excessive Exhaust Gas Temperature

Causes:

  • Engine operation in altitude.
  • Incorrect engine air/fuel ratios.
  • Malfunctioning exhaust oxygen sensor or other engine control system.
  • Malfunctioning EGR valve.

Symptoms:

  • Oil leakage
  • Noise
  • Loss of power
  • Excessive smoke

Consequences:

  • Erode, distort, or crack the turbine housing.
  • Wheels rub the end housings.
  • Imbalance to the rotating assembly.
  • Thrust bearing / journal bearing collapses.

Surge or Shaft Motion Operation

Causes:

  • Engine operation in altitude.
  • Application not in accordance to the standards.
  • Restricted air admission systems.
  • Malfunctioning EGR or PCV valves.

Symptoms:

  • Oil leakage
  • Noise
  • Loss of power
  • Excessive smoke

Consequences:

  • Damage to the compressor wheels.
  • Imbalance to the rotating assembly.
  • Thrust bearing / journal bearing collapses.

Broken Compressor Wheel

Causes:

  • Low cycle fatigue operation.
  • Application not in accordance to the standards.
  • Engine operation in altitude.
  • Wheel blades design.

Symptoms:

  • Oil leakage
  • Noise
  • Loss of power
  • Excessive smoke

Consequences:

  • Compressor wheel burst.
  • Compressor wheel broken as a ‘slice of pizza’.
  • Imbalance to the rotating assembly.
  • Excessive wear to the rotating assembly.

Excessive Exhaust Back Pressure

Causes:

  • Excessive engine brake operation.
  • Restricted exhaust systems.
  • Restricted air admission systems.
  • Malfunctioning EGR or PCV valves.

Symptoms:

  • Oil leakage
  • Noise
  • Loss of power
  • Excessive smoke

Consequences:

  • Back of turbine wheel rubbing center housing or heat shield
  • Scoring and wear of thrust bearing and thrust collar.
  • Imbalance to the rotating assembly.
  • Excessive wear to the rotating assembly.

Overspeed

Causes:

  • Incorrect engine air/fuel ratios
  • Malfunctioning exhaust oxygen sensor or other engine control system.
  • Malfunctioning wastegate actuator or its wrong calibration.
  • Application not in accordance to the standards.

Symptoms:

  • Oil leakage
  • Noise
  • Loss of power

Consequences:

  • Scoring the wheels to the housings.
  • Imbalance to the rotating assembly.
  • Excessive wear to the rotating assembly.