If foreign substances, such as dust, sand, screws, parts of piston rings or valves, and sediments, enter on the intake or exhaust side, this will usually lead to total failure of the turbocharger due to the very high speeds. Damage to the charge air cooler might also be the consequence.

- On account of previous damage, foreign substances from the engine or the exhaust manifold can damage the gas entry edges of the turbine wheel.
- The air guide plates of the VTG unit are damaged and bent , leading to a significant power loss.
- Foreign substances in the intake air result in damage to the impeller. The vanes might become completely worn as a result. In addition, the intake passage of the compressor housing might be damaged (Fig. 3).
- The impeller might be damaged by condensation frozen in the intake section. Damage to just one vane is characteristic of this cause: owing to the high speeds, the ice particles burst when encountering the first vane, with no other vanes being damaged .

- If a valve is torn off or the piston rings fracture, for example, these parts come into contact with the guide vanes of the VTG unit and the turbine wheel via the exhaust manifold.
- Both a leakage in the intake section and a contaminated or defective air filter can be the cause of penetration by foreign substances in the intake section.
- In winter, ice can form through condensation in the intake section.

- The leak tightness of the intake section must be guaranteed.
- After working on the intake section, it must always be ensured that no loose parts remain there.
- The air filter must be replaced as specified by the manufacturer, and the air filter housing as well as charge air line should be cleaned by suction.
- Only driving short distances should be avoided.