1999 GMC Yukon Owner's Manual - Page 305

yellowblue The following explains your cooling system and how to add coolant when it is low. If you have a problem with engine overheating, see "Engine Overheating" in the Index. A 50/50 mixture of clean, drinkable water and DEX-COOLR coolant will: NOTICE: Your radiator cap is a 15 psi (105 kPa) pressure-type cap and must be tightly installed to prevent coolant loss and possible engine damage from overheating. Be sure the arrows on the cap line up with the overflow tube on the radiator filler neck. Thermostat Engine coolant temperature is controlled by a thermostat in the engine coolant system. The thermostat stops the flow of coolant through the radiator until the coolant reaches a preset temperature. When you replace your thermostat, an ACR thermostat is recommended. D D D D D Give freezing protection down to -34_F (-37_C). Give boiling protection up to 265_F (129_C). Protect against rust and corrosion. Help keep the proper engine temperature. Let the warning gages work as they should. NOTICE: When adding coolant, it is important that you use only DEX-COOLR (silicate-free) coolant. If coolant other than DEX-COOL is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the NOTICE: (Continued) Engine Coolant The cooling system in your vehicle is filled with DEX-COOLR engine coolant. This coolant is designed to remain in your vehicle for 5 years or 150,000 miles (240 000 km), whichever occurs first, if you add only DEX-COOLR extended life coolant. 6-25