How to Flush a Coolant System

by Jerel Jacobs

Most people don't even think about their automobile cooling system until they are left stranded with a car that is overheating. Keeping your coolant system in top condition is vital to the life of your engine. This guide will instruct you on how to properly flush and change your vehicles cooling fluid.

Flusing Your Vehicle Coolant System

Make sure that the engine has not been running for awhile, and is cool. If the engine has been running the fluid will be very hot and under extreme pressure, and could injure you when you open the radiator cap.

Find the drain valve on the radiator to drain it. The drain valve should be on the bottom of the radiator. Drain the fluid into a bucket, do not allow it to run onto the ground. Once you have drained the radiator completely, close the drain valve.

You are now ready to install a back flush kit. These kit are relatively inexpensive and can be purchased at your local auto parts store. Follow the instructions on the back of your particular kit. In summary, you will have to cut the heater inlet hose going to the top of the engine. That is where you will install the T section provided in the kit into the coolant line. Slip both ends of the hose onto this fitting and tighten the clamps that came with the kit. Now, you can connect your garden hose to this fitting.

Place the diverter that came with the kit into the opening on the top of the radiator. This is where the water and coolant will pour out from when begin flushing the coolant system. A hose or tube will be useful to direct the water into a bucket.

Start the engine, turn the heater on high and turn on the garden hose. The coolant should begin circulating through the engine and coming out through the diverter on the top of the radiator. Continue this process until clean water begins to come out the top. This should only take several minutes.

Turn off the engine and garden hose. Next, drain the radiator again into a bucket and close the drain valve when you are done.

Now it is time to add the new anti freeze. Pour the entire contents of the anti freeze bottle into the empty radiator and fill it until coolant pours out of the neck. Screw the radiator cap back on and the job is complete. Don't forget to screw the cap back on for the T fitting you installed also.

Take a quick test drive to ensure that everything is working properly.


  • check Installing the back flush kit will make things go much quicker the next time you flush your radiator.
  • check Dispose of the used fluid properly. Call your local auto parts store as they will be able to recycle it for you.
  • check Never work on the radiator when the engine is hot.


  • close Radiator fluid is poisonous. Do not leave it out where children or pets can reach it.
  • close Do not allow radiator fluid to run down the drain. Dispose of it safely.
  • close Always double check and inspect your work carefully.

Items you will need

About the Author

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