- The smallest foreign substances in the oil cause grooves in the bushings (Fig. 1). The piston rings in the turbocharger can undergo serious wear. As worn piston rings can no longer adequately seal the turbocharger, the oil enters the turbine side, which can be discerned by increased oilconsumption.
- The bearing play of the rotating assembly increases due to the worn bushings. This leads to wobbling movements and causes the turbine wheel or impeller to come into contact with the housing . The shaft might subsequently break off.
- The bearing collar, i.e. the thrust washer of the axial bearing, exhibits grooves.
- Grooves or fretting marks are discernible in the axial bearing.
- Due to a blocked oil return line, the oil in the turbocharger can no longer flow off and is instead forced out to the compressor and turbine side. On the turbine side, the oil might then burn onto the shaft and coke. Owing to the oil carbon layer, the bearing housing and the piston rings might be significantly worn off as a consequence.
- The shaft of the turbocharger shows clear signs of wear at the bearing points



- If the maintenance intervals are exceeded, the oil filter can no longer filter enough dirt out of the oil. In this case, the dirt particles penetrate through the open bypass valve of the oil filter into the engine circuit.
- If the engine is operated with a blocked oil filter, the small abrasive particles cannot be filtered out of the oil.
- If the cylinder head gasket or the oil cooler is leaking, water will enter the oil circuit and dilute the oil. Its carrying capacity is thus reduced.
- If the engine was repaired, but not properly cleaned before assembly, dirt will be in the engine even before putting it into operation for the first time.
- The charge air cooler was not replaced. Accumulated engine oil, chippings, or fragments from the prior damage usually find their way into the engine with a time delay.
- If the engine is subject to considerable wear, the mostly metallic wear debris also finds its way into the turbocharger via the oil circuit.
- If combustion faults occur in the engine, non-combusted fuel can end up in the oil. The carrying capacity of the oil is reduced by this dilution.



- The maintenance intervals according to the manufacturer's recommendations should always be complied with.
- Only high-quality oil filters specified for the respective vehicle should be installed.
- Only engine oils specified by the vehicle or engine manufacturer may be used.
- A new charge air cooler and air filter should always be installed when replacing the turbocharger. In addition, an oil change including oil filter replacement must be carried out.
- The air filter housing and charge air line should be cleaned by suction.