How to Add Water to Engine Coolant
Adding water to your engine coolant may seem counter intuitive, but if done correctly using a mixture of water and coolant will protect your vehicle better against freezing up or boiling over than antifreeze alone. While you can top off your radiator with water, using a hydrometer or refractometer ensures it reaches the appropriate freeze protection point. Combining the coolant and water outside the vehicle first usually provides better results.
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Things You'll Need
- Clean 2 gallon or larger container
- Distilled water
- Undiluted antifreeze
- Large funnel
Instructions
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Consult your vehicle's manual to determine its coolant capacity. This is the total amount of liquid--water and antifreeze combined--that can go into the engine's cooling system. Secure a clean container that is large enough to hold the amount of coolant you'll be filling into your vehicle--usually 2 gallons or more.
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Combine 1 part distilled water to 1 part undiluted antifreeze (check the antifreeze bottle to make sure you're not using a pre-diluted mix) in the clean container. This is the ideal ratio for most driving conditions and will offer freeze protection down to -34 degrees Fahrenheit and boil over protection up to 265 degrees Fahrenheit for most engines. Experts recommend that, even in extremely cold conditions, your mixture should be at least 2 parts water for every 3 parts antifreeze or at the very least 3 parts water for every 7 parts antifreeze.
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Remove the radiator cap from your radiator and place a large funnel in the neck of the radiator. Make sure the petcock (drain) at the bottom of the radiator is closed. Carefully pour the water-antifreeze mixture through the funnel into the radiator. You may need to pause periodically to allow air to come up out of the radiator as coolant goes in. Fill the radiator to the fill line, which is usually 1 inch below the neck of the radiator.
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Remove the funnel and set any remaining coolant mixture aside for the moment. Start your vehicle with the radiator cap still off. Make sure the parking brake is on and that the vehicle is in neutral or park depending on what sort of transmission it has. You can also chock the wheels for added safety. Run the vehicle until it reaches normal operating temperature and topping off the level in the radiator as necessary.
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Turn off the vehicle's engine and replace the radiator cap. Check the coolant reservoir (a plastic bottle usually located near the radiator) for a line marked "MIN" or "Minimum." Fill the reservoir up to the minimum line with your coolant mixture.
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Dispose of any leftover coolant mixture in the hazardous waste or household chemicals disposal section of your local dump or landfill. Under no conditions should you pour it down a drain, into a gutter or out onto the ground. The chemicals in antifreeze are both very poisonous and very sweet-tasting, and tend to attract animals and small children that may then die as a result of poisoning.
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