A decrease in engine power may be your first indication your turbocharger is damaged or has failed.
Any nicks, scratches, or chips on either wheel are evidence foreign object damage caused by contaminants entering the airflow to or from the engine.
Axial end play of the wheels and shaft in and out greater than the thickness of a sheet of paper indicates a worn thrust bearing due to excessive exhaust backpressure.
Before a failed turbocharger is replaced the original cause of failure must be diagnosed and corrected to protect the new installation.
Common signs of wear indicating replacement may be required:
Worn engines with excessive blow by will result in crankcase pressurization, leading to oil leaking from the turbochargers internal seals. This may result in oil deposits in the intake manifold or smoke in the exhaust. This is not necessarily a sign of a failed turbocharger, but rather a sign that the engine needs to be rebuilt or replaced.