Chevrolet 2005 Aveo Owner's Manual page 211

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. 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.
2. Then keep turning the pressure cap slowly, and
remove it.
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