2009 Chevrolet Silverado 2500 HD Extended Cab Owner's Manual - Page 441

Checking Coolant The coolant surge tank is located in the engine compartment on the passenger side of the vehicle. See Engine Compartment Overview on page 5-14 for more information on location. The vehicle must be on a level surface when checking the coolant level. Check to see if coolant is visible in the coolant surge tank. If the coolant inside the coolant surge tank is boiling, do not do anything else until it cools down. If coolant is visible but the coolant level is not at or above the FULL COLD mark, add a 50/50 mixture of clean, drinkable water and DEX-COOL® coolant at the coolant surge tank, but be sure the cooling system is cool before this is done. The coolant level should be at or above the FULL COLD mark. If it is not, you may have a leak in the cooling system. If the vehicle has a low coolant sensor and the LOW COOLANT LEVEL message comes on and stays on, it means you are low on engine coolant. See "LOW COOLANT LEVEL" under DIC Warnings and Messages on page 3-66. 5-31