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DO NOT USE a chemical flush to flush your coolant system. Various methods and equipment can be sued to flush the cooling system. If special equipment is used, such as a back flusher, follow the manufacturer's instruction. However, ALWAYS remove the thermostat before back flushing the system.
Procedures are below..
Block the drive wheelsPlace the transmission in Park (P) or Neutral (N)Engage the park brakeRun the engine until the thermostat opensStop the engineDrain the old coolant and refill with clean drinkable water. Repeat this step if necessary, until the water is nearly colorless.Fill the coolant reservoir to the FULL COLD markFill the cooling system SLOWLY with a mixture of 50/50 DEX-COOL antifreeze and deionized water until the coolant level reaches and maintains slightly above the cold fill line on the surge tank. With coolant pressure cap INSTALLED start the engine and run it at 2,000 - 2,500 RPM for 3 minutesAllow the engine to idle for 30 secondsShut off the engine and top off coolant as necessaryFill the coolant reservoir to the cold fill lineInspect the cooling system for leaks and inspect the concentration of the coolant mixture.
Air can sometimes enter the cooling system lines when flushing the system. If this occurs and you experience overheating after the flush, remove the radiator pressure cap and run engine for a few minutes. This will allow the air to escape from the cooling system.