1997 GMC Sonoma Owner's Manual - Page 215

A 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. When the coolant in the coolant recovery tank is at ADD, 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