Refer to Engine Troubleshooting. Excessive exhaust temperatures can damage the turbocharger either directly or indirectly. With direct damage, excessive temperatures overheat the center housing and actually erode or distort the turbine housing material. Results of the distortion can be found on the turbine housing contour. Turbine wheel rub can result slowing shaft speed and aggravating the problem.
Heat moves down the shaft from the turbine toward the compressor, damaging the journal bearings.
Oil in the center housing cokes and builds-up deposits adding to the bearing failure process and finally leading to shaft motion. Turbine housing cracking can also result from excessive exhaust temperatures. Indirect damage from excessive exhaust temperatures occurs when the rotating assembly begins to turn faster than its designated operating speed due to the additional heat energy. If this happens, the compressor wheel may burst apart because of a single or repeated high stress load. The turbine wheel may burst apart because of the reduced strength from high temperatures and the elevated speed.