Pontiac 2007 Solstice - Manual (Page 266)

{ 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. 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 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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