Turbocharger Bearing Failure
A turbo charger is lubricated by the engine's oil. It’s vital to change the oil and coolant at recommended intervals. This is because old and contaminated oil will surely damage a turbocharger's bearings. Today’s turbochargers spin well in excess of 100,000 RPM. That’s incredible! These speeds combined with the hot exhaust spinning the turbine wheel create great heat. This is why they’re so often cooled by the engine's cooling system.
This heat is why many manufacturer's recommend cooling the turbocharger by idling the engine for a minute or two before shutdown. When the engine is shut down immediately after an average drive, the oil will harden and little pieces will get into the bearings causing turbocharger bearing failure. When the bearings are faulty, a whining sound will result. This will also damage the shaft and housing. As the bearings wear, the blades on the turbine and compressor wheels can get damaged from the excessive end-play.