1995 GMC Sonoma Owner's Manual - Page 196

When you decide it's safe to lift the hood, here's what you'll see: A. Coolant recovery tank B. Radiator pressure cap C. Engine fan If the coolant inside the coolant recovery tank is boiling, don't do anything else until it cools down. The coolant level should be at the ADD mark. If it isn't, you may have a leak in the radiator hoses, heater hoses, radiator, water pump or somewhere else in the cooling system. 5-12