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Does Antifreeze Evaporate Over Time?

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Engine antifreeze, also called engine coolant, plays a crucial role in keeping your engine working properly. Sometimes, you may notice that your antifreeze level is low even though you see no signs of leaking fluids. So, does antifreeze evaporate over time? We dove into this matter for you, and here's what we found out.

Yes, if antifreeze is exposed to the air, it will evaporate slowly over time. However, in a completely sealed container or system, the antifreeze will not evaporate.

You might be wondering why you keep having to top up your car's antifreeze from time to time, even if you don't see any leaks on your garage floor. Keep reading, and we'll help you understand more about this matter.

Pouring blue antifreeze to the car, Does Antifreeze Evaporate Over Time?

Is My Coolant/Antifreeze Getting Low Because It Is Evaporating?

Before we go any further, let's get one terminology issue out of the way. Because modern antifreeze solutions prevent freezing in cold temperatures and also cool down the engine, it is safe to say that coolants and antifreeze products are one and the same.

Pouring pink antifreeze liquid to the car engine

What Is My Engine's Coolant Solution Made Out Of?

Whether you bought a concentrated or a prediluted coolant product, one thing remains the same: your engine's coolant solution needs to be approximately 50% water.  

Most concentrated coolant products consist of approximately 80-95% ethylene glycol base plus some lubricating and protective additives, coloring dye, and bittering agent. Before use, this concentrated product needs to be diluted in a 1:1 ratio with water.

Some modern coolants use propylene glycol instead of ethylene glycol as a base. Although it is less effective at regulating temperatures, propylene glycol is also less toxic.

As the name implies, prediluted coolant products have the same chemical components, but they are premixed with water, which makes the product ready to be used immediately.

Check out this prediluted coolant on Amazon.

So what do all of these imply? If your car's coolant solution does evaporate, it will be the water component that evaporates far more easily.

Ethylene Glycol

In its pure form, ethylene glycol is hydrophilic, hygroscopic, and has low vapor pressure. Now that's a mouthful. What do these terms mean?

  • Hydrophilic means that ethylene glycol mixes easily with water.
  • Hygroscopic means that ethylene glycol absorbs moisture from the air.
  • Low vapor pressure means that ethylene glycol needs a relatively high temperature for it to turn into vapor or gas.

These three characteristics mean that ethylene glycol has a very low tendency to evaporate into the air. This tendency becomes even lower when ethylene glycol is stored in a fully sealed system or container.  

Sealed Cooling System

Almost all modern cars on the road nowadays have sealed cooling systems. These systems were designed to be maintenance free and are drained only when there is physical damage or when the coolant needs to be replaced. The coolant should not evaporate in this sealed system and should never need topping off.

This is true if the system is really fully sealed. Now here you need to ask yourself a question. Is your car's cooling system fully sealed?

If your engine coolant is constantly getting low, your cooling system is not fully sealed. This means you may have holes, cracks, or leaks in your radiator, tubes, hoses, reservoir, or even inside your engine.

Why Does My Coolant Keep Disappearing?

Pouring blue anti freeze into the container

Large Leaks

If you see colorful droplets or puddles on your garage floor or parking space, then it may be a telltale sign of a large leak in the system. The most common sources of these obvious coolant leaks are as follows:

  • Radiator cracks or holes
  • Busted radiator cap
  • Cracked reservoir
  • Damaged tubes or hoses
  • Loose or broken tube ends or hose clamps

While some seasoned car enthusiasts may be able to fix these leaking points themselves, the average car owner may need some professional help.

If you are somewhat a DIY person, you might want to read this helpful article about fixing antifreeze leaks: Antifreeze Leaking From Car – What Could Be Wrong?

No Obvious Leaks

Most small leaks can come from hairline cracks or tiny holes from the same cooling system components previously mentioned. Coolant solutions heat up after passing through the engine block and thus can escape as steam through these tiny gaps in an otherwise sealed system.  

You can try locating these leaks yourself while at home using a radiator/coolant pressure tester.

Check out this radiator pressure tester on Amazon.

Coolant Escaping From Reservoir

As the coolant expands from the engine's heat, it is forced out of the radiator into the reservoir or overflow tank. The hot coolant can degrade the plastic material of this tank over time and thus lead to tiny cracks in the reservoir body or cap.

Because heat increases the vapor pressure of the coolant, the hot liquid solution can steam out of these tiny openings in the reservoir.

Head Gasket Damage (A Big Headache)

Another possible cause for the disappearing coolant is a leak inside the engine, particularly in the head gasket.  

A damaged head gasket will allow the coolant solution to enter the engine's combustion chambers. There, it will be burned off and expelled through the engine's exhaust. Below are some indicators of a damaged head gasket.

  • Cloudy/milky discoloration in engine oil 
  • A watery leak from the tailpipe
  • Thick white smoke from the tailpipe
  • Bubbling coolant liquid in the reservoir or radiator
  • Lower engine power
  • Overheating engine

A damaged head gasket is quite a big and expensive problem to solve. Repairing or replacing the head gasket often requires professional help and specialized automotive tools.  If you see these signs in your engine, it may be time to schedule your car for servicing.

Of course, if you have the tools and the expertise, you might want to repair your car's head gasket yourself.

Check out this head gasket repair product on Amazon.

What Is Engine Coolant?

An internal combustion engine (ICE) retains a third of the heat it produces during operation.  Without a proper cooling system, ICE engines can reach 600 to 1,500 degrees Fahrenheit. For reference, aluminum melts at 1,200 degrees Fahrenheit. 

The vehicle's cooling system, which includes the coolant, is responsible for regulating this heat. Coolant products not only raise the boiling temperature of the water but also act as the lubricating and protective agent for the water pump, head gasket, and many others.

On the other hand, the coolant liquid also serves as the antifreeze solution during frigid weather. The base chemical of the solution significantly lowers the freezing point of water, thus preventing the cooling liquid in the engine block and the radiator from icing up.

If you only use water for your car's cooling system, then it may freeze during winter. If, after a biting-cold night, you are somehow still able to start your car, then the frozen water will not be able to circulate. Your engine will most probably overheat and suffer some damage.  

How Coolant Works Under The Hood

When an engine is running, the coolant runs its course to absorb the heat and then releases it as the coolant solution passes through the radiator. Once the coolant liquid passes through the radiator, it becomes cool enough for another cycle.  

Most coolant products need to be in a 50/50 mixture with water to achieve the best results.  Why is this so?  Water is still better than EG for absorbing heat. However, water has a relatively low boiling point, and water cannot protect the engine parts well from friction and corrosion.

This is where the coolant's chemicals come in. The EG improves the heat transfer capability of water, while the additives provide lubrication and corrosion protection to engine parts.

As an antifreeze, your coolant solution plays a more inactive but vital role by keeping the water in its liquid form during frigid weather.

Types Of Coolants

Pouring blue antifreeze liquid

While all coolant products are glycol based, they differ mostly because of their additives.

Inorganic Acid Technology (IAT) Coolants

IAT coolants have inorganic additives that protect engines well from corrosion. These coolants are commonly used for older cars because these vehicles had iron engines that were prone to corrosion.

Organic Acid Technology (OAT) Coolants

As the name implies, OAT coolants have purely organic additives. They offer less protection, but they last longer than IAT coolants.

OAT coolants work better for newer aluminum engines.

Hybrid Organic Acid Technology (HOAT) Coolants

HOAT coolants have both IAT and OAT attributes. These hybrid solutions have organic additives that prolong coolant life and inorganic additives that offer better engine protection.

Lobrid Coolants

"Lobrid" coolants are varieties of HOAT Coolants. Compared to regular HOAT coolants, Lobrid coolants use more organic additives than inorganic ones in their formulation. Two examples of Lobrid coolants are:

  • P-OAT coolants - Phosphated Organic Acid Technology
  • Si-OAT coolants - Silicated Organic Acid Technology

Is It Okay To Mix Different Antifreeze Types?

Pouring green antifreeze coolant to the engine

The different types of coolants have been specifically formulated for the specific requirements of different cars.  

For instance, mixing different types of coolants can cause a chemical reaction that can change the viscosity and texture of the solution. This action can result in a thicker, gel-like compound that cannot flow well through the cooling system.

Finally, mixing different coolants can cause particle buildups or clogs in the cooling system. These clogs will cause the engine to overheat and eventually damage components like the water pump, radiator, head gasket, etc.

Wrapping Up

Pouring blue antifreeze to the car

If an antifreeze solution remains inside a sealed cooling system, it will not evaporate. In reality, however, our cars' cooling systems can develop tiny holes or gaps that allow the hot coolant liquid to evaporate over time.  

It is always best to be vigilant in checking your coolant levels to help avoid major problems in the cooling system.

Thank you for reading, and we hope you were able to learn a thing or two about whether antifreeze evaporates over time. Also check out these interesting articles about engine antifreeze, its uses, and benefits:

What Happens If You Mix Coolant Colors?

Does Coolant Level Drop When Engine Is Hot?