The turbocharger is one of the most misunderstood products in the automotive industry. If the vehicle starts to emit smoke the turbocharger will invariably get the blame.
A turbocharger operates in an extremely harsh environment - 1050°C exhaust gas/turbine temperature and over 200,000-RPM rotor speeds are not uncommon operating conditions for an automotive turbocharger.
Appreciating this will help you understand why a turbocharger will fail if the engine or supporting systems are not in good order.
The main life-sustaining factor for a turbocharger is the lubricating oil, comparable to the blood supply for a human being.
More often than not a defective turbocharger is the consequence of some other primary engine defect which cannot be cured just by replacing the turbocharger.
A turbocharger is only as good as the engine it is fitted to and the person fitting it cannot expect a new turbo to cure underlying engine problems.