How Do You Flush a Radiator?

Flush your vehicle's radiator by draining the coolant, refilling it with chemical flush product and water, starting the vehicle and bringing it to operating temperature, draining a second time, and refilling the radiator with an antifreeze mix. This job completes in the span of an afternoon.

  1. Drain the coolant

    Start the job after the vehicle is cool. Place a container under the drain plug to catch antifreeze as it drains, then open the drain port and radiator cap. Do not allow antifreeze to drain on the ground.

  2. Add the chemical flush

    Close the drain valve, and add the chemical flush product. Add water to fill the radiator. Close the radiator cap.

  3. Start the engine

    Start the car and bring the car to operating temperature. Turn the heater to its highest setting and allow the car to continue operating. Normally, running the engine for about 10 minutes is sufficient. Once the engine is hot, turn it off and allow it to cool.

  4. Empty the catch container

    Empty the container so it is ready for the second draining. Pour used coolant into plastic water jugs and label them as antifreeze. Place the container back under the drain plug.

  5. Empty the chemical flush

    Open the radiator cap, and drain valve a second time to drain the chemical flush. Collect the liquid in the catch basin and transfer to bottles for proper disposal.

  6. Refill the radiator

    Close the radiator drain again, and fill the basin with a 50 percent antifreeze mixture. Replace the radiator cap to complete the job.