Pontiac 1995 Grand Prix Owner's Manual page 196

NOTICE:
In cold weather, water can kreeze and crack the
engine, radiator, heater core and other parts. Use
the recommended coolant.
When the coolant in the coolant recovery tank is at the
COLD mark, start your vehicle.
If the overheat warning continues, there's one more
thing you can
try.
You can add the proper coolant mix
directly to the radiator, but be sure the cooling system is
cool before you do it.
5-17