What to Do if Too Much Water is Added to Car Antifreeze

Cars in a lot.
What You'll Need
Bucket or pan
Distilled water

Car antifreeze is something most people don’t think about too often. They’ll usually check it and add some if it’s low or, when it’s discolored, they’ll flush it and refill. You should be aware that having too much water in your car antifreeze can be dangerous to your engine.

Step 1 - Understand What Antifreeze Does

Antifreeze stops water freezing in your engine when the temperature is really cold. It also has another function, to stop the liquid from becoming too hot. For all intents and purposes, antifreeze and coolant are exactly the same thing. The chemicals in antifreeze stops corrosion in the engine. Antifreeze helps disperse much of the heat in the engine. Without it, the metal parts of the engine would melt. It gathers the heat from the engine in the liquid and moves it away, replacing it with fresh, cool liquid. This liquid cools as it circulates.

Step 2 - Don't Add Too Much Water

You need to have the right proportion of antifreeze and distilled water for your engine to work properly. Improper dilution is the main cause of engine failure. You also need to be aware that you should never use water from the faucet in the engine’s cooling system. The greatest problems you’ll find with too much water in your car antifreeze that it will freeze at a higher temperature, and also boil at a lower temperature. That means a more limited operational range of temperature for your vehicle.

Step 3 - Check the Amount of Antifreeze

If you believe that you have too much water in your car antifreeze, you’re going to need to use a refractometer to measure just the percentage of antifreeze that’s actually in the coolant. An ideal mix is 50 percent antifreeze and 50 percent distilled water. In very cold climates that ratio should be 60 percent to 40 percent.

Step 4 - Drain Antifreeze

If after checking you find too much water in the antifreeze, you’re faced with two options. If you’re low on car antifreeze, you can add more antifreeze and test again to see if the strength is correct. A much surer way is to drain the old antifreeze and refill with the correct mixture. To drain it, you’ll need to place a bucket or pan under the car to catch the old car antifreeze. Don’t let it soak into the ground or run into the drain. Antifreeze is toxic, and it can kill animals and have an adverse effect on the water table. You need to dispose of it responsibly. Your auto parts store will be able to tell you where to take it.

Open the drain plug at the bottom of the radiator and allow the antifreeze to drain completely. This will take some time. When you’ve finished, close the drain plug and refill the coolant system with car antifreeze. You can buy pre-mixed or you can buy concentrate and add the appropriate amount of distilled water yourself.