Hobbies Cars & Motorcycles Checking and Filling Your Coolant/Antifreeze Share PINTEREST Email Print Reza Estakhrian/Iconica/Getty Images Cars & Motorcycles Cars How Tos Buying & Selling Basics Reviews Tools & Products Classic Cars Exotic Cars Corvettes Mustangs Tires & Wheels Motorcycles Used Cars SUVs Trucks ATVs & Off Road Public Transportation By Matthew Wright Matthew Wright has been a freelance writer and editor for over 10 years and an automotive repair professional for three decades specializing in European vintage vehicles. our editorial process Matthew Wright Updated May 25, 2019 Most people know the green stuff in your radiator keeps your engine from turning into a block of ice in the winter, but did you know that it also helps keep things cool in the summer? All too often people are driving around with just water in their radiator because they think they don't need the green stuff until it gets cold. This is not the case. Radiator coolant, also known as antifreeze, actually raises the boiling point of the water, too, allowing it to carry more heat away from the engine. That means cooler running. If you're running low, things can get steamy fast. Think of your coolant as a spring dance chaperone, there to keep things nice and cool even when you're doing a lot of moving around. Make sure you are confident about how your cooling system works. Check the Level Luckily it only takes a second to check your coolant level. Most cars these days have a translucent coolant overflow tank right next to the radiator. It's white plastic, but you can see inside to see if there's enough juice to keep things safe. You'll also see markings on the side telling you the low and high levels to work with. Always check your coolant level when the car is cold. If you happen to have an older vehicle without a visible overflow and fill tank, you'll have to check the antifreeze/coolant level by looking into the radiator. There is no dipstick or another meter to tell you whether you have enough coolant in the radiator on these older vehicles. The good news is that the older systems were much less sensitive to how much coolant you had—or didn't have—in the radiator. As long as you can visibly see the level of the coolant by removing the radiator cap and looking into the top of the radiator, your level is fine. The following piece of information is very important: Do NOT attempt to open the radiator cap on a hot car. The system is highly pressurized and the fluid inside is very hot. The combination of the two can mean some serious burns if it starts to spray out. Patience. If You're Still Low If your levels are good, no need to go any further, enjoy the peace of mind. But if you're low, you'll need to top it off. Your engine takes a 50/50 mixture of coolant and water. That's a mixture of half water, half coolant In the old days, you had to make measurements yourself and test the mixture to get it right. But since we live in the age of convenience, you can now buy pre-mixed coolant that's ready to pour. For a simple topping off, I recommend going this route. It might cost a buck more, but you're in for much less mess. To add the coolant, simply unscrew or pop off the cap on top of the opaque plastic overflow reservoir and add your mixture until it reaches the full mark. Now put the cap back on nice and tight and you're ready for any weather. It's a good idea to flush your radiator to clear out any gunk and prevent electrolysis due to the breakdown of old coolant. There are a few issues that can result from a low coolant level, outside of the obvious overheating problems that led you to this point in the first place. Did you know that a low coolant level can cause you to have no heat? Keeping your cooling system in top shape is super important to the longevity of your engine and your vehicle's systems. Don't skimp on this type of maintenance. Safety Point If you spill any coolant on the ground while you're filling, be sure to wipe it up. Coolant is very toxic to animals, but they like to drink it because it tastes sweet. Save a little furry life!