Troubleshooting on the exhaust turbocharger
For charged engines, exhaust turbochargers are of significant importance to the power development. The turbochargers deliver the charging pressure that is required by the engines. Depending on the system (one-phase or multi-phase), one or more turbochargers are installed. However, the function of the turbocharger greatly depends on the proper function of other components in the periphery.
This document describes the sources of fault on the actual exhaust turbocharger as well as the factors influencing and causing faults in the periphery.
The following figures show examples of the schematic structure of one-stage or two-stage systems with the required actuators.
|3||Exhaust gas||4||Fresh air|
Two-stage system, shown simplified and by way of example. The charging system is also a two-stage system on engines with 3 and 4 exhaust turbochargers!
|1||Compressor bypass plate||2||Compressor high-pressure stage|
|3||Turbine high-pressure stage||4||Turbine control flap|
|5||Wastegate valve||6||Exhaust gas|
|7||Turbine low-pressure stage||8||Compressor low-pressure stage|
|9||Fresh air||10||Low pressure compressor bypass flap|
Sectional view of turbocharger
|1||Turbine housing||2||Turbine wheel|
|3||Variable blades||4||Adjusting ring|
|5||Oil inlet journal||6||Adjusting lever|
|7||Electrical turbocharger pressure adjuster||8||Compressor housing|
General notes on troubleshooting
The following notes must be observed in order to find the root cause of faults when problems are reported, and to prevent the unauthorised, i.e. inappropriate, replacement of the exhaust turbocharger:
Tracking down and verifying the complaint
If possible, any problem reported ('complaint') should be tracked down and verified on the vehicle. The parameters or marginal conditions prevailing at the time the problem was reported need to be noted down.
As a first procedural step, diagnosis must be performed using the diagnosis system.
Faults on sensors and actuators may be responsible for 'complaints', i.e. reported problems, which may also be associated with the exhaust turbocharger in some way. For this reason, faults on sensors and actuators must first be remedied if these are stored in the fault memory.
In addition, the engine ventilation is important for the oil supply to the exhaust turbocharger. If the pressure in the crankcase is too high, the oil supply to the exhaust turbocharger is endangered, and oil leakage may occur at the exhaust turbocharger.
The stored charging pressure control faults must then be investigated or troubleshooting must take place on the exhaust turbocharger.
If possible, check to find out whether repairs have already been made on or near the exhaust turbocharger following similar reported problems.
- With any repeated complaint with different fault patterns, the problem could have arisen during the last repair. Problems could have arisen in conjunction with installation, connections or the ingress of foreign bodies.
- In the event of identical complaints, it is highly probable that the actual cause of the fault has not been remedied.
Notes on the installation of an exhaust turbocharger
- Prior to the installation of an exhaust turbocharger, fill engine oil in the oil inlet in the exhaust turbocharger. At the same time, rotate the shaft on the exhaust turbocharger.
- Check the oil supply to the turbocharger and the oil return from the turbocharger for foreign bodies and oil sludging, clean if necessary.
- Ensure that no dirt and no foreign bodies enter the openings.
Clean the charging air system.
Note: Do not leave any oil residue or foreign bodies in the charge air duct.
- Replace gaskets, and ensure that the gaskets are installed correctly.
- Observe tightening torques.
- Start up engine and run it at idle speed for at least one minute to ensure that the exhaust turbocharger is receiving a proper oil supply. When the engine is cold and the ambient temperature is low, let the engine idle for approximately 2 minutes.
- Check tightness of oil lines.
- Stop engine, check oil level.