Volvo VHD - Manual (Page 206)

200 Engine Start and Operation
Stopping the Engine
Allow the engine to slow down and idle for
3 to 5 minutes before shutting it off. This
allows the turbo to slow down and the
cooling system to dissipate the engine heat.
Switch the engine off by turning the igni-
tion key to the O, or OFF, position.
CAUTION
Shutting off an engine immediately after
high speed or full load operation can
damage the turbo and cause heat stress
in the engine. Always let the engine idle
for 3 to 5 minutes before shutting it off.