How to Flush Your Radiator and Replace the Coolant

Flushing the radiator and replacing the coolant is something that must be accomplished periodically. This is done to prevent your engine from overheating and keep the inner workings of your cooling system free from contaminants. You can always delegate this task to a certified mechanic, but if you want to save on maintenance expenses, or prefer to get your hands dirty from time to time, a radiator flush is easy enough to do, and you can even perform it in your own garage or driveway.

What you'll need

Make sure you have the following things handy before you begin:

  • Drain pan/bucket (with at least 15-liter capacity)
  • Screwdriver or wrench (depending on your type of drain plug)
  • Radiator flush solution
  • Distilled water
  • Running faucet with hose (a pail of water will also do)
  • Fresh coolant

Prep the car

Park your vehicle on a flat surface, and make sure the engine is cool to the touch. Keep pets and children away from the work area, as coolant is poisonous. Have your pan or bucket ready underneath the drain plug to catch the spills.

Drain the coolant

Remove the radiator cap and drain plug. The radiator cap will be located on top of your radiator, and the drain plug somewhere at the bottom. If you don’t know where the drain plug is, check your owner’s manual, or do a visual inspection. Depending on your vehicle type, the drain plug will either be a screw, bolt, or petcock that you can open by hand. Open the drain, then let the coolant flow until it stops. Put the plug back in to close the drain, then dispose of the waste in an environmentally-friendly way.

Add the radiator flush solution

Pour your radiator flush solution through the open radiator cap, then fill it to the top with water. Replace and tighten the radiator cap, then start the car and let the engine run for up to 10 minutes. Make sure you have the gear on neutral before you do. Afterwards, turn the engine off and wait for it to cool. Never open the radiator cap if the engine is still hot to the touch as you could get scalded by the hot water inside the radiator.

Drain the radiator flush solution

Once the engine has cooled, replace your pan or bucket underneath the radiator, then open the drain plug and let the solution flow. Replace and tighten the drain plug once it’s done.

Refill the radiator

Check your owner's manual to learn the number of liters or quarts that your cooling system holds. Many coolant products today come diluted with distilled water, but if you're pouring pure coolant, you will have to pour only half of the cooling system's capacity and then fill the rest with distilled water. You may need to use a funnel to avoid spills.

Run the engine to circulate the fresh coolant

Tighten the radiator cap, then run the engine for up to 10 minutes to disperse the coolant and water evenly throughout the system. Turn off the engine, and you're done.

Make sure to dispose of your used coolant properly. Likewise, check your radiator after a few days of use to ensure the coolant level is optimal. If it is low, add equal parts coolant and distilled water to the reservoir.

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