is received via inlet 40 and passages 42 44 this cooling oil flow by its traverse through passages 42 44 its flow from bearings 16 18 and its flow across the internal surfaces of oil drain gallery 46 absorbs heat from and cools the turbocharger 10 the turbocharger 10 also liberates heat to its environment by radiation and convection from external surfaces also heat may be transferred to air traversing the compressor wheel 24 and flowing to the air outlet via chamber 38 the summation of these heat transfer effects results in the bearings 16 18 operating at temperatures low enough to prevent oil coking therein further as a consequence the materil 52 is maintained in a relatively low energy molecular state upon shutdown of the engine supplying exhaust gasses to inlet 30 both the source of heat energy and the source of cooling oil flow to the turbocharger cease to operate however both the turbine housing section 28 and turbine wheel 22 are hot and hold a considerable quantity of residual heat this residual heat is conducted to the cooler parts of the turbocharger much as heat was conducted during operation thereof however no cooling oil flow or internal compressor air flow is now present consequently the temperature of shaft 20 and center housing 14 progressively increase for a time over their normal operating temperatures this temperature increase if uncontrolled could result in temperatures at bearings 16 18 and particularly at the latter which would degrade or coke.