1995 GMC Yukon Owner's Manual - Page 256

Cooling System- Diesel Engines ... , - ..::* When you decide it's safe to lift the hood, here's what you'll see: A. Coolant surge tank pressure cap B. Engine fan(s) C. Radiator If the coolant inside the coolant surge tank is boiling, don't do anything else until it cools down. The coolant level should be at or above the COLD 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. 5-18