2009 Chevrolet Cobalt Owner's Manual - Page 289

4. With the coolant surge tank pressure cap off, start the engine and let it run until you can feel the upper radiator hose getting hot. Watch out for the engine cooling fan. By this time, the coolant level inside the coolant surge tank may be lower. If the level is lower than the COLD FILL line, add more of the proper mixture to the coolant surge tank until the level reaches the COLD FILL line. 5. Then replace the pressure cap. Be sure the pressure cap is hand-tight and fully seated. See your dealer/retailer, if necessary. Coolant Surge Tank Pressure Cap 3. Fill the coolant surge tank with the proper mixture, to the COLD FILL line on the tank. Wait about five minutes, then check to see if the level is below the COLD FILL line. If the level is below the line, add additional coolant to bring the level up to the line. Repeat this procedure until the level remains constant at the COLD FILL line for at least five minutes. Notice: If the pressure cap is not tightly installed, coolant loss and possible engine damage may occur. Be sure the cap is properly and tightly secured. The coolant surge tank pressure cap must be fully installed on the coolant surge tank. See Engine Compartment Overview on page 5-12 for more information on location. 5-31