Nearly everyone and their parents have stories about going out on a fine autumn morning just to see their antifreeze (or coolant) running low. We’ve all been there, and it’s not a pleasant experience. 

When it happens, a question would probably pop up in your mind: Can you use water as coolant? Well, you are not alone. Many people out there believe that they can use water to replace antifreeze when they have no other choice. While this might sound tempting, it’s definitely not something Drive Revolve would recommend. 

Why, you ask? Read until the end: This article can help you avoid some catastrophic breakdowns or accidents. 

About Coolant And Its Importance 

What is coolant
The primary purpose of coolant is to absorb heat and prevent engine damage caused by boiling or freezing – Source: Smart Mechanics

Although there is a slight difference between the two, the terms “antifreeze” and “coolant” are often used interchangeably. 

Antifreeze is made of propylene and silica. These key ingredients can lower water’s freezing point and increases its boiling point. This helps water in your radiator stay in liquid form, preventing it from boiling, evaporating, or freezing. Thanks to that, the engine can always run at an optimal temperature. 

Antifreeze comes in various colors, such as blue, green, orange, pink, red, and yellow. Since each type has a distinctive color, drivers can tell which one is right for their vehicles. 

When mixed with distilled water in a 50/50 ratio, it becomes a coolant. As you jumpstart your car, the engine generates massive heat. The cooling system will channel coolant flow into the passage of the engine block and the cylinder heads. As the coolant goes through the engine, it will absorb the heat. 

The heated fluid then travels to the radiator. As it passes through the radiator’s tubes, the air flowing through the front of the car will cool it off. 

The fluid that has been cooled flows back out of the radiator and into the engine. The cooling system operates on this circulation of coolant, ensuring that the engine stays cool. 

Now you see why coolant is vitally important to the vehicle’s overall health: Without it, the engine would be overheated, resulting in numerous problems that are expensive to repair. Not only can the head gasket blow, but the cylinder head might also warp, leading to severe engine damage. 

Can You Use Water As Coolant? 

Can You Use Water As A Coolant?
Can you put water in the coolant tank? – Source: Mechanic Base

In short, yes, you can. 

It’s always recommended to fill the system with an appropriate coolant mix. Due to various reasons, though, leakage may occur. If you are in an emergency and don’t have access to anything except water, using it as coolant should be enough to take the car to the auto repair shop. 

Nonetheless, water is not a permanent solution. Looking at the differences between water and coolant, you will understand why water is incapable of protecting your engine: 

Boiling Point 

In case you don’t know, the boiling point of water is 212°F. This is much lower than the operating temperature of your car. Obviously, water alone wouldn’t be enough to cool off the engine. 

When you combine water with propylene glycol antifreeze using the 50/50 ratio, this boiling point will be increased to 223°F. That’s not too far off from the engine’s operating temperature. 

So, if you don’t use antifreeze, the vehicle’s engine will overheat. As the liquid inside boils over and evaporates, your vehicle will stop so the motor can cool down. By letting the engine overheat, you also risk significantly damaging it.

Freezing Point

Ironically, it’s suggested right at the name, but many forget this effect of antifreeze/coolant: Aside from protecting the engine from heat, it also prevents the radiator from freezing. 

That’s because the mixture of antifreeze also lowers the freezing point of water. Even when the temperature outside drops, your car’s engine block can stay at a constant temperature thanks to the antifreeze circulated through it. 

If you live in a colder climate, the absence of antifreeze will result in the water freezing inside the engine. Consequences include cracking the radiator, warping the cylinder head, and damaging the engine block. 

Corrosion Protection 

There are many types of minerals within the water. After a while, they will form deposits within the radiator. These prevent the radiator from functioning properly. What’s more, water tends to be corrosive to metal, so rust will build up more quickly. 

Both of these are deadly to the engine, which is why coolant contains special additives that prevent rust formation. Using water alone doesn’t ensure a long life for the metal parts. 

How To Put Water In The Car: A Step-By-Step Guide 

Now you see why it’s not ideal to use water as a coolant. Under any circumstances, never fill the coolant tank with water when the outside temperature is extremely cold. The water will freeze inside your radiator, making the problem worse. 

Nonetheless, when the weather is mild, your engine temperature is rising, the coolant level is really low, and you only have water at hand, temporarily adding it to the vehicle can be a choice. In fact, it’s better than running your car with little to no fluid at all. 

With that in mind, here are the steps to safely fill the coolant tank with water. 

  • Step 1: Park your vehicle with the parking brake on and double-check the engine to ensure that it’s turned off. 
  • Step 2: Wait until the engine has thoroughly cooled down to an ambient temperature, 
  • Step 3: With the engine cooled, you can now remove the coolant reservoir’s cap. If you try to remove the cap while it’s still hot, the remaining coolant may splutter, causing burns if it comes in contact with your skin. 

In most cases, this cap should be found along the upper radiator tank. Other cars will have the caps at the remote overflow reservoir. 

Remember to remove the cap slowly and cover your hands with a piece of cloth. Again, you wouldn’t want to have hot coolant sprayed on your hands, arms, and face. 

  • Step 4: Slowly fill in the highest quality water you have until it reaches the “full” mark
  • Step 5: As you’ve added water, it’s time to “burp” your engine’s cooling system of air. Simply allow the engine to idle without the fill cap. At this point, you will see small bubbles on the water’s surface. 

Keep burping until the engine has reached the operating temperature. At this point, you might need to add some more water, then reinstall the fill cap. Make sure it’s secure by turning until it clicks, and close the bonnet of the vehicle. 

  • Step 6: Keep a watchful eye. The engine is more likely to overheat with water, so don’t put it under pressure. Drive slowly and stop occasionally – this gives the radiator time to cool down. 
How to put water in your radiator?

For more detailed instructions, you can check this guide on how to put coolant in cars

Frequently Asked Questions 

When Can You Fill Coolant To The Radiator Again? 

If you are caught in a tricky situation when you have to use water as the coolant, take your car to the auto repair shop as soon as possible. The technician will address the problems, repair any leaks, and help you flush the radiator before filling it with the coolant again. 

Remember, you should only add coolant after flushing it thoroughly. 

Does The Type Of Water Matter? 

Though any type of water is not intended to replace coolant completely, some of them can be more friendly to the engine than others. This is because particular types of water have a greater risk of causing corrosion and scale buildup inside the cooling system. 

Ideally, you should use distilled water for coolant.  Purified or soft water are good alternatives if you don’t have distilled water at hand. Avoid using tap water since it contains several minerals that are catalysts for corrosion. Filling the coolant tank with tap water can accelerate the formation of unfavorable deposits, thus compounding overheating-related problems. 

How Often Should You Check Engine Coolant?

To prevent leaks, the best way is to check your engine coolant frequently. As a rule of thumb, it should be checked at least twice a year, before summer and winter. Automobile technicians advise topping it up as soon as the level drops below the guide marks or whenever you see a warning sign on the dashboard. 

Wrapping Up

So we have answered the burning question, “Can you use water as coolant?” Water by itself can’t do the job of antifreeze due to its narrow range of freezing and boiling point, as well as the inability to safeguard your vehicle’s engine. 

In the case of an absolute emergency, you can use it as a temporary solution. However, we highly advise you to get your car to an auto repair shop as soon as possible afterward so it can be re-filled with the proper fluids. 

Do not overlook other exciting posts in our Fun Autopart Section.

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