GMC C series 2002 Owner's Manual page 191

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.
Specialty Hood
5-24
When the coolant in the coolant recovery tank is at the
HOT LEVEL mark on the vehicle with the specialty
hood, or approximately half full on the vehicle with the
sloped hood, start your vehicle.
If the overheat warning continues, there's one more
thing you can try. You can add the proper coolant
mixture directly to the radiator, but be sure the cooling
system is cool before you do it.
Sloped Hood
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. Don't spill coolant on a hot engine.