How to Flush a Radiator

February 23, 2012

Maintaining a radiator requires more than maintaining water and antifreeze levels. Learning how to flush a radiator is crucial.

Radiator Maintenance

Knowing how to flush a radiator comes in handy if there is a lot of build up or contaminants in your coolant, or the balance of antifreeze to water is off, which can damage your cooling system. Before you remove any radiator fluid, ensure that no pets, small children or anything that can harm themselves is, or can go anywhere near your car.

Tools and Materials

  • Receptacles for catching radiator fluid
  • Water
  • Coolant
  • Radiator cleaning fluid
  • A funnel
  • A cloth

Clear Your Work Area
Radiator fluid is poisonous, so ensure that your work area only has people in it that need to be there, and it is clear of small children or animals. They tend to like radiator fluid as they find it sweet. It will kill them.

Drain the Old Radiator Fluid
Ensure the radiator is cool. Place one of the receptacles under the car to catch the fluid, and then locate the drainage plug. It will either be screw or bolt plug, in which case remove it completely, or a petcock, in which case open it all the way. If you cannot find the radiator drainage plug, refer to your owner's manual.

Clean the System
Once all the liquid has been drained, attach and tighten the radiator drainage plug. For a petcock tighten the valve. Remove the radiator cap and pour in the radiator cleaning fluid and top up with water. Put the cap back on and tighten.

Circulate the Fluid
Start the car's engine until it reaches operating temperature. This is when the temperature gauge reaches where it normally would be for everyday use. Turn your heaters on maximum and let the engine run for a further 10 minutes. Switch off the engine and allow it to cool.

Drain the Radiator Flush Solution
Place another receptacle under the car, and once you are sure the radiator is cool, remove the drainage plug as in Step 2. Let all the cleaning fluid drain out. Once this is complete, replace and tighten the plug.

Refill the Radiator and Water Reservoir
Using the funnel, add a 50/50 mix of water and radiator coolant to the radiator, and then the desired mix of water and antifreeze to the water reservoir of the car. Ensure you do not add too much antifreeze.

Clean up and Dispose of Waste Liquid
All your tools should now be cleaned and put away, and the waste liquid should be taken if possible to a recycling center where it can be disposed off safely. Ensure there are no spills, even small ones.

Check your radiator levels in a day or two to ensure they are at the right level. Air bubbles can work their way into the system during a flush, and this can cause problems in the future.