Chevrolet 2004 Aveo Owner's Manual page 218

CAUTION:
{
You can be burned if you spill coolant on hot
engine parts. Coolant contains ethylene glycol
and it will burn if the engine parts are hot
enough. Do not spill coolant on a hot engine.
1. Park the vehicle on a level surface.
You can remove the coolant surge tank pressure
cap when the cooling system, including the coolant
surge tank pressure cap and upper radiator
hose, is no longer hot. Turn the pressure cap slowly
counterclockwise (left) about two or two and
one-half turns. If you hear a hiss, wait for that to
stop. This will allow any pressure still left to be
vented out the discharge hose.
5-32
2. Then keep turning the pressure cap slowly, and
remove it.