GM Service Manual Online
For 1990-2009 cars only
  1. Block the drive wheels.
  2. Place the transmission in Park or Neutral.
  3. Engage the park brake.
  4. Start the engine.
  5. Run the engine until the thermostat opens.
  6. Shut off the engine.
  7. Drain the cooling system. Refer to Cooling System Draining and Filling .
  8. Follow the drain and fill procedure using ONLY clean drinkable water, repeat if necessary, until the fluid being drained is colorless.
  9. Fill the cooling system. Refer to Cooling System Draining and Filling .