What Happens If My Coolant Freezes? How to Fix

Frozen coolant has several challenges that can damage a vehicle’s engine components. While the coolant plays a vital role in heat transfer and engine protection, the fluid must not be allowed to reach too extremes – boiling or freezing.

You may be wondering, “What happens if my coolant freezes?” The experience is not good, as it can cause severe damage to your vehicle’s engine components. Now you’re curious to know precisely the effect of a frozen coolant in a car.

 Carefully read the subsequent sections of this article below to know the effect of a frozen coolant, how to unfreeze a car’s radiator, and the best way to avoid a frozen coolant in your car.

what happens if my coolant freezes

What Happens If My Coolant Freezes?

If your vehicle’s coolant freezes, the liquid will crystallize and block your engine’s passageways. As the coolant is in solid form, it will be difficult to flow across and absorb heat from the engine block. This will expose the engine to heat build-up, which can be detrimental to the engine and its related components.

 Some engine problems are exceptionally costly to fix. Therefore, it is essential to do everything possible to avoid any occurrence that poses a challenge to your vehicle’s engine, especially a coolant freeze.

 In addition, the kind of coolant used in your car during winter has a great role in the extent to which the fluid can contend with the freezing possibility in cold temperatures. This can be more serious for those in the northern part of the country, where the weather can be extremely cold.

What is Antifreeze?

Antifreeze is a key component in car coolant. It is an additive that lowers the freezing point of the coolant within an engine’s cooling system. This ensures that the vehicle operates efficiently and safely in cold and hot weather conditions.

The most common type of antifreeze is ethylene glycol, although propylene glycol is also used as a less toxic alternative. These substances are mixed with water (usually in a 50:50 ratio) to create coolant, which circulates through the engine to absorb and dissipate heat, preventing the engine from overheating. Additionally, antifreeze contains corrosion inhibitors and other additives to protect the engine and cooling system components from rust and corrosion. Thus, it minimizes car problems.

Ethylene glycol-based antifreeze is highly effective at reducing the freezing point of the coolant, which prevents the liquid inside the engine and radiator from freezing even in extremely cold temperatures.

At What Temperature Will A Car Engine Freeze?

A car’s engine will eventually freeze around -36 degrees Fahrenheit (-38 degrees Celsius). When this occurs, it will be difficult for the coolant to flow through and absorb the heat from your car’s engine.

 However, the temperature at which a car’s engine freeze depends on the fluid used as a coolant in the radiator. In other words, the antifreeze-to-water ratio is vital in determining whether your engine will freeze faster during cold temperatures.

 For instance, a car’s engine would freeze around -36 degrees Fahrenheit under a standard antifreeze-to-water ratio of 50/50. Meanwhile, the engine would freeze around -84 degrees Fahrenheit at an antifreeze-to-water ratio of 70/30.

 Typically, the presence of the antifreeze in the coolant helps to slow down the water molecules’ coalescence when atmospheric temperatures drop to a level that can cause the fluid to freeze.

 However, ordinarily, antifreeze has its coolant freezing point around 0 to -5 degrees Fahrenheit. Meanwhile, this freezing point changes when mixed with water depending on the mixture ratio.

 Furthermore, using only water as a coolant in the radiator is not ideal. Sometimes, you may be tempted to use this option, especially during an emergency. However, this approach exposes the radiator to freezing up faster (at 32 degrees Fahrenheit) than when the actual coolant is used.

 If you’re wondering, “what happens if water freezes in radiator?” It will automatically seize up the flow of fluid within the cooling system, allowing heat to build up in the engine.

Why Did My Coolant Freeze?

Your car’s engine coolant froze due to the fact that the fluid may have degraded over time or the antifreeze-to-water ratio is imbalanced. In other words, when the fluid in a cooling system boils off, and you replace it with water, the 50/50 antifreeze-to-water ratio will eventually be altered.

Therefore, when the coolant fluid consists of more water than antifreeze, the liquid will most likely freeze faster than when you have the ideal 50/50 Valvoline Coolant and water ratio in the radiator.

So, if your coolant freezes during winter, it is most likely that the fluid has degraded and needs a replacement. However, it could also be based on having excess water than antifreeze in your cooling system. Therefore, ensure to avoid these two situations.

What to Do If Coolant Freezes

Can coolant freeze? Of course, you know that coolant can already freeze up around -36 degrees Fahrenheit. So, if your engine’s coolant freezes, especially during winter, get a fan heater in front of your car’s radiator and blast the hot air directly to the radiator.

The heat from the fan will eventually melt down the frozen coolant over time. However, you may experience some damages if you delay before implementing this remedy. For instance, the crystallized and expanded fluid would have probably cracked the cooling system tubes.

Therefore, it would be best to always use the ideal coolant fluid with the recommended 50/50 antifreeze and water ratio for your car to avoid such an occurrence.

How to Unfreeze A Car Radiator

Unfreezing a car’s radiator is pretty straightforward. However, the whole process can be time-consuming, depending on the method you choose to use. The following are some recommendations on how to unfreeze a car radiator.

Park the car in a warm garage

Once you notice a frozen radiator, kindly find a way to move your car from outside, where it is exposed to cold temperatures, especially in winter. Ensure to move the car by pushing it into a warm garage.

The heat from the warm garage can work on the frozen antifreeze and melt it gradually. However, this can take a long time, even days, to melt down completely. Therefore, you may have to move to the next stage below.

Blow hot air directly into the radiator

Get a hairdryer or heater fan. Having one that blows a very high heat level will make the process faster. Once you have the dryer or heater fan, position the component directly to the radiator and blast the heat against the radiator.

As the heat intensifies in the radiator, the frozen coolant will start melting gradually. You may want to stay on this process for some minutes until you completely transform the crystallized coolant into liquid.

refilling coolant

Drain the fluid and replace it with fresh coolant

After melting the frozen coolant into liquid, ensure to drain the fluid from the cooling system and replace it with the recommended coolant containing 50% antifreeze and 50% water. Again, it would be best if you have pre-mixed coolant to ensure the ratio is balanced.

As a matter of importance, it is advisable to do everything possible to keep your car’s engine coolant from freezing in the first place by using the recommended coolant at all times, especially during winter.

How Do I Keep My Engine From Freezing Overnight?

There are several ways to keep your car’s engine from freezing overnight. Some of the strategies are outlined below.

Store the car in a warm garage

This method is one of the easiest ways to keep your car’s engine from freezing overnight. Sometimes, you may feel reluctant about driving your car into the garage. So, you allow it to stay outside till the next day.

However, you should make it a strict policy to park your car in the garage during winter in order to protect it from the cold temperatures that can freeze the engine overnight.

Attach an engine preheater to your car

A preheater can also help sustain your engine’s heat and prevent it from freezing overnight. A preheater is a device that is plugged into a wall socket. The device is inserted into your car’s coolant through the radiator hose.

As the preheater warms up the coolant, it transfers the heat across the vehicle’s engine to protect it from freezing.

Use an electric blanket

An electric blanket also plus into a wall socket like a preheater. It generates heat and helps to keep the engine warm overnight. So, kindly get an electric blanket, spread it over your car’s engine, and close the hood to prevent heat from escaping.

This will help keep the engine warm throughout the night during winter so that it can start quickly in the morning.

Place a lightbulb under the hood

Placing a 150-watt lightbulb under your vehicle’s hood overnight may not do much, but it can also keep the engine compartment warm. In addition, this will help the engine start faster than when you leave the component exposed to cold temperatures at night during winter.


If you’re asking, “what happens if my coolant freezes?” The possible damage that this occurrence can cause to your car has been unveiled above in this article. Therefore, it is vital to do everything you can to avoid this experience.

However, if your car’s radiator is frozen, use a powerful heater fan to melt the solid and drain the old coolant out of the radiator. Then, replace the fluid with a fresh coolant immediately.

Solomon Osuagwu

Osuagwu Solomon is a vetted auto mechanic with over ten years of experience in the garage and five years of experience as a service writer. He prides himself in writing accurate information on professional repair guides, DIY repair guides, buyer’s guides, comparisons, and car reviews. If he’s not in his repair garage, he’s writing automotive blogs to help car owners and fellow mechanics to troubleshoot and proffer solutions to several car problems.

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