How Do You Clean a Car Radiator?

clean-car-radiator Credit: Tuan Tran/Moment/Getty Images

A radiator can be cleaned by first opening the petcock (radiator drain valve) and draining the existing coolant fluid from the radiator. Once all of the coolant has been drained, close the petcock and fill the radiator with water. Flush the radiator by opening the petcock and draining the water from the radiator. Add new coolant and bleed the air from the radiator. Bleeding is done by leaving the cap off the radiator, starting the vehicle and letting it run for about 15 minutes. After the air has been bled, add additional coolant and replace the radiator cap.

  1. Prepare car radiator

    Allow the engine to cool for at least two hours before starting the cleaning process. Open the radiator petcock and drain all the fluid into a pan for proper disposal. Close the petcock.

  2. Flush the radiator

    Using water or a radiator flushing solution fill the radiator. Once full, open the radiator petcock and drain. Capture the fluid and dispose of properly. Close the petcock.

  3. Complete cleaning

    Fill the radiator with new coolant fluid. Bleed any trapped air in the radiator by leaving the radiator cap off and running the engine for about 15 minutes. After bleeding, add any additional coolant fluid as needed and replace radiator cap.