Does Coolant Evaporate? (All You Need To Know Explained!)

Many car drivers notice that their coolant is disappearing. This is not good for car drivers because coolant is vital to the engine of all vehicles. If you have the same observation, let us talk about the reason behind it. 

So does coolant evaporate? The answer is yes, coolant does evaporate naturally. This is the explanation why you might notice that your coolant is disappearing even without leakage. 

Every vehicle needs fuel to run and it also needs engine oil to operate, but every vehicle needs coolant too. All the fluids inside the vehicle are important and they play a different role and a different function for the engine of a vehicle. With that, you should always monitor your coolant and if your coolant is sufficient enough to do its job.

In the automobile world, there is internal combustion, and this internal combustion will be heated up. There is also the movement of many mechanical parts and the electric oil generating current. There is also the air conditioning unit. 

The primary function of a coolant will be to lessen the engine temperature in summer. It must also increase the engine temperature in winters if you drive in extreme climates. The level of the coolant must remain sufficient all the time. 

But as mentioned, there are times where you would notice that your coolant is disappearing. There can be a lot of reasons why your coolant would go away. 

In this article, we will be talking about that. Let us start. 

Does Coolant Evaporate

Does Coolant Evaporate Over Time?

Yes, coolant does evaporate over time. Because of extreme engine temperature, the element of water in the coolant will evaporate. This will then drop on your coolant. 

And because there is the presence of an overflow reservoir, it will make the one end of the coolant open, and it will spill out extra coolant, or it can jump out of the system. The leak in the coolant will cause an overheated engine, and it can result in an engine failure and cause a large number of repairs.

 If you use the wrong type of coolant or drive a car with a low coolant in its reservoir, the vehicle’s engine can overheat. The reasons can be many, and it will depend on the condition of the vehicle, the condition of the weather, the driver, or a faulty engine component. 

Does Coolant Evaporate If Left Open?

We are not experts with the coolant chemicals, and we cannot tell the evaporation rate of ethylene glycol, but if you have the cap off to leave it open, the water can evaporate from the mixture. This is because the cooling system of the vehicle is pressurized. 

If the cap is removed, there will be no pressure, and the cooling system will not circulate correctly. As a result, there can be overheating. There will also be evaporation in the radiator. 

How Fast Does Coolant Evaporate?

The vehicle will get more old. With that, the coolant will evaporate more also. In a standard calculation, every year the engine passes by, the coolant will drop to 0.25 in four months. 

This is with the provision that the engine functions very well and there are no damages or leaks. So 0.25 inches quarterly will make one inch for every year. 

The evaporation of the coolant can be expected in extreme temperatures, which will turn the water element within the coolant into steam. So it is advised to have a clean-up in your radiator after a few years.

Does Coolant Evaporate In Hot Weather?

Coolant will evaporate in a frosty white stain. If the humidity is less than 50%, then it would be seventy-two hours. Your coolant will disappear over time because of evaporation because of the natural steaming process, engine equipment failure, or disruption of the coolant flow. 

There can also be a leak within your radiator or a crack and broken hose. You have to ensure that your engine is cooled down. If you need to add to the coolant reservoir, you have to ensure that the engine is switched off before opening the tank. 

There is pressure in the system, and it can cause burns. And there might be some correlation between the disappearance of your coolant and the hot weather. 

Does Coolant Evaporate In Cold Weather?

You have to keep in mind that low temperatures can affect the coolant of your vehicle. This is because there are particles inside the coolant that will contract in cold weather. So if the days are freezing, it can trigger a low coolant in your vehicle. 

Does Coolant Evaporate On The Ground?

Yes. If the coolant is in the ground. The coolant will most likely evaporate. However, it can also leave a slight oil residue or stain. 


In summary, many car drivers have been noticing that their coolant is disappearing in their engines. Coolant does evaporate. 

Coolant has water in it and some other chemicals, and it can also evaporate. The weather might have something to do about it also.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more