Cooling System: Service and Repair

DRAINING AND REFILLING

WARNING: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the radiator cap while the engine is hot and pressure is high will cause the solution to boil instantaneously - possibly with explosive force - spewing the solution over engine, fenders, and person removing cap. Under some conditions, the ethylene glycol in engine coolant is combustible.

1. Completely drain the system by opening the drain cock at the bottom of the radiator. If the coolant is dirty, or if there are deposits in the radiator, flush the cooling system before refilling.
2. Remove the cooling system pressure cap. Clean, test and inspect the radiator/cooling system filler neck.
3. Disconnect all hoses from the coolant reservoir. Remove the reservoir and pour out any fluid. Scrub and clean the inside of the reservoir with soap and water. Flush it well with clean water then drain it. Install the reservoir and hoses.
4. Close the radiator drain cock (and install the block drain plugs if removed).
5. Refill the cooling system with a coolant meeting GM Specification 6277M. To ensure sufficient engine cooling, freezing and corrosion protection, maintain the protection level at -37°C (-34°F) or lower. Use a solution that is no more than 70 percent antifreeze.
6. Place the heater-A/C control in any A/C mode except "MAX" and the temperature in the highest setting.
7. Allow the engine to continue idling until the lower radiator to coolant pump hose is hot.
8. Cycle the engine speed up to about 3000 rpm and back to idle five times. Slowly open bleed valve on the rear of the thermostat housing for approximately 15 seconds to expel any trapped air In the cooling system.
9. After the air has been expelled, fill the radiator. Install the radiator pressure cap, making sure the arrows on the cap line up with the coolant recovery tube.
10. Allow engine to cool to outside temperature, then check the coolant level in the reservoir. If not at the "ADD" (of "FULL COLD") mark, add coolant until it is.