Chevrolet 2011 Volt Owner's Manual page 384

When it is safe to lift the hood:
A. Engine Coolant Surge Tank and
Pressure Cap
B. Engine Cooling Fans
(Out of View)
The electric cooling fans under
the hood can start up even when
the engine is not running and
can cause injury. Keep hands,
clothing, and tools away from
any underhood electric fan.
If the coolant inside the coolant
surge tank is boiling, do not do
anything else until it cools down.
The vehicle should be parked on
a level surface.
The coolant level should be up to
the cold fill line. If it is not, there
might be a leak at the radiator
hoses, heater hoses, radiator,
water pump, or somewhere else
in the cooling system.
Heater and radiator hoses, and
other engine parts, can be very
hot. Do not touch them. If you do,
you can be burned.
Do not run the vehicle if there
is a leak. If you run the engine, it
could lose all coolant. That could
cause an engine fire, and you
could be burned. Get any leak
fixed before you drive the vehicle.
If there seems to be no leak,
with the engine on, check to
see if the electric engine cooling
fans are running. If the engine is
overheating, the fans should be
running. If it is not, the vehicle
needs service. Turn off the vehicle.