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they are unnecessary.

the turbo is cooled by an auxiliary electric water pump. if the oil is excessively hot when the motor is shut down this pump runs coolant through the system -it runs in reverse of the normal direction so that it pulls coolant directly from the radiator and immediately hits the turbo bearing housing. if you listen carefully you can hear the wine of the pump running after a hot shutdown.

from the 2.0 TFSI design and function handbook:
"Cooling System
To prevent carbon build-up on the turbine
shaft in the turbocharger, an auxiliary
coolant pump provides additional coolant
circulation for a certain time after the
engine is shut off hot. The pump forces
the lower temperature coolant against the
normal direction of flow. The coolant flows
from the radiator through the turbocharger​
to the engine block and back to the cooler."
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