This Preliminary Information communication provides information to the technician about vehicles that have a under hood odor that is coming from the engine coolant. Technician will need to completely drain the cooling system and refill it is with drinkable water and one bottle of GM Heavy Duty Cooling System Cleaner. After the cooling system is completely full drive the vehicle for 40-60 minutes with the heat on high. Technician should allow the engine to cool then completely drain the cooling system. After the cooling system is completely drained, fill the cooling system with water and run the engine for 10 minutes to circulate the water. Technician should allow the engine to cool then completely drain the cooling system. After the cooling system is completely drained, technician will also need to remove the surge tank and thoroughly clean it with hot water. Now install the clean surge tank and fill the cooling system with water and run the engine for 10 minutes to circulate the water. Technician should completely drain the cooling system and replace all the cooling hoses. Technician will install the thermostat using a new water pump inlet seal. After the new hoses and thermostat is installed fill the cooling system with Premixed DEX-Cool or a 50 / 50 DEX-Cool water mixture.
