GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 General Information 🢒 General Information 🢒 Flushing

Important: 

   • Do not use a chemical flush.
   • Store used coolant in the proper manner, such as in a used engine coolant holding tank. Do not pour used coolant down a drain. Ethylene glycol antifreeze is a very toxic chemical. Do not dispose of coolant into the sewer system or ground water. This is illegal and ecologically unsound.
   • Various methods and equipment can be used to flush the cooling system. If special equipment is used-such as a back flusher-follow the manufacturer's instructions. However, always remove the thermostat before back flushing the system.
  1. Block the drive wheels.
  2. Place the transmission in park (P) or neutral (N).
  3. Engage the park brake.
  4. Run the engine until the thermostat opens.
  5. Stop the engine.
  6. Follow the drain and fill procedure using only clean drinkable water. Repeat the procedure if necessary, until the fluid is nearly colorless. Refer to Cooling System Draining and Filling .
  7. Fill the coolant surge tank to the FULL HOT mark. Refer to Cooling System Draining and Filling .