Saturn 2006 Ion Owner's Manual page 270

Notice: In cold weather, water can freeze and crack
the engine, radiator, heater core and other parts.
Use the recommended coolant and the proper
coolant mixture.
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.
5-34
1. You can remove the coolant surge tank pressure
cap when the cooling system, including the upper
radiator hose, is no longer hot. Turn the pressure
cap slowly counterclockwise about one-quarter of a
turn. 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.