Pontiac 2003 Montana Owner's Manual page 354

Steam and scalding liquids from a hot cooling
system can blow out and burn you badly. They
are under pressure, and if you turn the
radiatorpressure cap
-
even a little
-
they can
come out at high speed. Never turn the cap
when the cooling system, including the
radiator pressure cap, is hot. Wait for the
cooling system and radiator pressure cap to
cool if you ever have to turn the pressure cap.
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