How To Check & Test Antifreeze For Cold Weather

Though you may think antifreeze is only used to cool your engine and may not be as necessary in colder weather, checking and refilling your coolant can help you better prepare for winter and protect your vehicle's engine from freezing temperatures. Coolant, also commonly called antifreeze, not only helps your engine stay at the correct operating temperature, but is also designed to maintain a lower freezing point than plain water. Coolant is transported throughout the engine and radiator to maintain a vehicle’s safe, stable operating temperature, and also helps protect from harmful mineral deposits or the development of rust scale that can lead to corrosion, clogs, or system damage. Not only can a lack of coolant impact your vehicle, but old or bad coolant can create a more acidic mixture, leading to internal corrosion and engine damage.

More importantly, as the temperatures begin to drop, ensuring that the condition and concentration of antifreeze in the system is sufficient to help prevent engine damage that may result from liquid freezing inside the engine’s coolant passages or the cooling system. You should check your coolant levels regularly, at least every three to six months depending on your car’s needs, and your vehicle’s owners manual may provide an appropriate coolant inspection interval. In addition to coolant level, checking your antifreeze's freeze point can help you properly prepare for colder weather and complete your winter car prep plan this winter.

How To Test Antifreeze

Your coolant’s freeze point helps you understand the temperatures your antifreeze can stand up to, and can tell you if your choice of coolant is appropriate for the weather conditions you experience in your area. The freezing point of coolant is vehicle-specific and dependent on the type of coolant you use since there are an array of types, mixtures, and engine- or climate-specific needs. It’s important to consider that water has a lower freezing point than fresh, concentrated antifreeze, so you are essentially testing the ratio of antifreeze and water for optimal performance. Most antifreeze on the market today offer freeze protection down to -34°F and boil-over protection up to 265°F. Ensure your coolant mixture is not below 40% or above 60% — this can cause engine damage or lack of cooling system performance. Your coolant’s current freeze point is found by using a coolant tester, also known as a bubble gauge, or refractometer. Since bubble gauge-style antifreeze testers are very common and affordable, we'll be describing their use in the remainder of this article.

4. Insert the antifreeze tester into the coolant.

5. Squeeze the bulb of your antifreeze testing tool. This will create a vacuum inside the tester that will suck coolant into the chamber, providing a sample of your vehicle’s coolant to test.

6. Stop filling the tester when the amount of liquid fills up to the top of the temperature measurements on the tool.

7. Observe the plastic beads or the dial indicator inside the tool. These are designed to float within the coolant tester, and will rise to the level of the lowest temperature your antifreeze can withstand.

8. If you notice these plastic beads are spread throughout the antifreeze tester, this can mean several things. The highest floating beads should be the only ones considered. Count the beads that are floating, and compare them with the levels on your bubble gauge. This can quickly and easily tell you the lowest temperature your coolant can experience before freezing.

Remember: On most antifreeze testers today, the number of beads floating correlates with its temperature performance. So, if you see two beads floating, locate the product’s user’s manual and read the related temperature. If your gauge reads 32°F, this is the temperature at which water freezes. This means that your engine will operate normally outside of cold climates, but consider your area’s average winter weather to discern what temperatures you need your coolant to protect against. If you live in Northern or especially chilly climates, you may need to change your coolant to maintain a lower freeze point, ensuring the safest cooling system performance.

Wait, My Coolant Can Freeze Or Bubble?

While it’s normal for your coolant to bubble a small amount as its temperature changes within the engine, there is a difference between this occurring due to normal operation and a cooling system issue. In extreme weather, coolant has both a normal boiling and a freezing point, depending on your vehicle’s antifreeze concentration and volume, and can be affected by local temperatures. Like all liquids, your car’s antifreeze can either boil over or freeze in especially high or low temperatures, preventing your engine from being protected against damage caused by overheating or freezing. Low coolant levels, coolant leaks, and more can result in boiling antifreeze, which could cause pressures inside the cooling system to rise and result in damage to your car’s engine, as well as overheating, and steam coming from under the hood. If you’ve noticed any of these issues you can learn more about why your car may overheat to prevent damage to the cooling system, a broken pressure cap or radiator, or worse, a blown head gasket. In the colder months of the year, knowing that your coolant’s freeze point is lower than the anticipated winter temperatures can also help you maintain a healthy, better-protected engine.

What Happens If Coolant Freezes In The Engine?

In low temperatures and winter weather, your coolant’s mixture is vital to delivering the cooling system and engine performance that you expect. Especially in cold temperatures, underperforming antifreeze formulas or concentrations can cause antifreeze in the cooling system and engine to freeze. This causes the liquid to expand, which could damage your engine block, cylinder heads, head gaskets, cooling system hoses, and freeze or expansion plugs. Cracked engine blocks, cylinder heads, or blown- or rusted-out freeze plugs can allow coolant to leak from the engine rapidly and require much more intensive repairs or a complete engine replacement.

Coolant is intended to be an exact mixture of deionized water and glycol, and if you use a concentrated formula, must be mixed with distilled water to reach the correct concentration. If your car’s coolant concentration is off, if you haven’t flushed and refilled the cooling system in a long time, or if your antifreeze is just not suited for the temperatures you experience in your area, this can affect the cooling system’s operation and overall health. Low coolant levels or high water concentrations can also lead to water deposits that may cause scale buildup or corrosion.

You can prevent your antifreeze from underperforming this winter by calculating your coolant’s freeze point using a bubble gauge or antifreeze tester. It’s recommended that you maintain a 50% ratio – half coolant and half distilled water – if you use an antifreeze concentrate. You can also use pre-mixed coolant to more easily achieve the correct ratio inside your cooling system.

What’s The Difference Between Antifreeze And Coolant?

Though the terms are often used interchangeably, coolant is actually the mixture of antifreeze, also known as ethylene glycol or propylene glycol, and water. Antifreeze by itself is entirely too strong to be used in a vehicle and is pre-mixed with a certain amount of water even in concentrated coolant formulas. This simply allows the end user to more easily mix concentrated coolant at a 50/50 ratio, but pre-diluted antifreeze and coolant is also available that is ready to add to your vehicle right out of the bottle. Your vehicle’s needs determine what type of coolant mixture is needed for stable, reliable operation.

As discussed, pure antifreeze and coolant are different — and that’s where a 50/50 antifreeze can come in handy. By pre-mixing the proper amounts of antifreeze and water, a 50/50 coolant helps ensure that your engine has an adequate concentration of coolant and the best possible protection against low temperatures. An antifreeze concentrate does not include the recommended amount of water, and will need to be mixed with an equal proportion of distilled water during filling. Again, antifreeze concentrates and coolant mixtures may be universal or vehicle-specific, and your type of vehicle, driving habits, manufacturer recommendations, and weather conditions can help you choose the best coolant for your car.

Make Sure Your Engine is Protected

Whether your antifreeze concentrations are too high or have been watered down, ensuring your coolant ratio is exact can help your vehicle perform better and protect against internal damage. If you realize that your antifreeze mixture is not correct, or if the coolant in your vehicle will not protect your engine at the lowest temperatures you might experience your area, the next steps include flushing and refilling your radiator with either pre-diluted coolant or concentrated coolant and distilled water to ensure the proper concentration for the best engine protection. Want to learn more about your car’s cooling system?

Visit our How-To Hub for a wide selection of topics and step-by-step instructions including basic cooling system tips, finding the right coolant for your car, types and colors of coolant, and much more to help you get the job done right the first time.