Saturn 2008 AURA Green Line Hybrid Owner's Manual page 251

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.
Turn the pressure cap slowly counterclockwise
about two or two and one-half turns. If you hear a
hiss, wait for that to stop. This allows any pressure
still left to be vented out the discharge hose.
1. 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.
2. Then keep turning the pressure cap slowly,
and remove it.
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