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Is Car Coolant Just Water

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Your car needs to retain a specific temperature for it to run smoothly. Get the temperature too low, and the car may refuse to start. But the most significant damage can occur when an engine overheats, as overheating can cause engine damage. For this reason, the engine uses water with a coolant solution added on to enable the engine to maintain safe operating temperatures.

This coolant solution has specially-made passages that enable it to cool the engine as it functions. Have you been wondering is car engine coolant just water? Or are you thinking of replacing radiator water with just engine coolant? Here, you learn how best to treat your engine in regards to using coolant. 

Is Car Engine Coolant Just Water?

Car engine coolant is not just water. It is a water-based coolant with antifreeze to enable it to keep the engine at the proper running temperature. It is added to the water in the radiator to raise the water’s boiling point so that it can endure the engine’s temperature and not boil over. 

A close look at coolant in a car

The coolant also has antifreeze that lowers the water’s freezing point so that it does not freeze when it gets cold. Since the engine produces a lot of heat as it operates, it needs constant cooling. Water has a high freezing and low boiling point, making it lack the properties to keep the engine cool efficiently.

How Does the Engine Coolant Work?

The engine coolant is taken through the engine using specialized piping to keep it at its optimum working temperature. Experts agree that an engine’s optimum temperature should be between 195 and 220 degrees Fahrenheit (87 to 103 degrees Celsius). For that to happen, the coolant has to flow through the engine at a high pace continuously.

Temperature gauge inside a car showing normal levels

The coolant also has to go through rapid cooling. The radiator cools the coolant as it comes heated from the engine. Once cooled, it can go back to carry the engine’s excess heat from it and back out to the radiator. 

When the car is in motion, the air cools down the radiator, and when the car is at a standstill, a fan attached to the engine keeps the radiator cool enough to cool the coolant. 

Should I Use Coolant or Water?

Your vehicle produces a lot of heat while running. Most of this heat dissipates with the help of the coolant running through the engine. The exhaust system also releases heat from the engine to maintain its optimum temperatures. 

A man about to pour coolant in a car

Coolant is formulated to maintain the engine’s optimal working temperature while preventing engine corrosion. It has a high boiling temperature, ensuring the engine’s temperature does not eliminate it through evaporation. It also has an antifreeze that prevents it and the engine from freezing.

Water boils at a low temperature, which would quickly evaporate from the engine. It also has no anti-corrosive or antifreeze properties to protect the engine from damage. You cannot replace the coolant with water because of these inadequacies. Water also introduces impurities like minerals into the engine, aiding in contaminants buildup.

A man pouring water in a car

Water can only serve as the engine’s coolant in an emergency when the coolant is running low or absent. And you can only use water for a short duration as you look for coolant to replace it. 

Is It Okay To Drive With Low Coolant?

The engine functions at optimum states to enable it to deliver the power needed to stay mobile. Your coolant’s reservoir has a minimum and maximum limit, ensuring that the engine always has the right amount of coolant moving through it to keep it cool. 

A car with a sufficient coolant level

Since the engine already has a set temperature range within which to operate at its best, increasing its operating temperature will damage it and eventually cause it to fail. Driving with low coolant means the car cannot cool down efficiently. Its temperature will rise to the point where engine parts get damaged and the car stalls.

Issues Arising From Driving With Low Coolant

Driving with low coolant gives rise to several issues, all of which can badly damage your engine. A complication from low coolant gives rise to a more severe complication until the engine gets damaged. 

The first complication your engine encounters when you drive with low coolant is having air pumped into the system through the water pump. Air gets sucked in by the water pump when it does not have enough coolant volume to move around the engine. 

A man calling for help due to an overheating car

The next event is that your engine will overheat since air does not have the proper cooling effect on the engine when distributed in the coolant system. If you do not stop and treat this emergency, the problem escalates to a blown gasket. A gasket sits between the cylinder head and the engine head and is very expensive to replace.

If the temperatures stay up and the gasket holds, the engine block will most likely get damaged or cracked. If that happens, you will need to replace the engine block, making it an even more expensive affair than the blown gasket.

Lastly, your engine has the potential to seize if the temperatures stay up so long that the metal parts expand and get damaged. Finding the damaged parts requires taking the engine apart to find the damage.  

Can You Mix Tap Water With Coolant?

You would be ill-advised to mix tap water with coolant as it comes with minerals and other impurities. These impurities cause radiator corrosion, reducing its lifespan. You should only use tap water as a first aid measure to prevent engine damage. 

A bottle of coolant beside a bottle of water

It would be best if you got to a radiator specialist at your earliest convenience to have them flash the radiator before filling it up with proper coolant. While some coolant types require mixing them with water, distilled water is the best to use in the radiator as it gives the highest purity. This mixture prolongs the radiator’s life and gives your engine the optimum working temperatures.

Can Water as Coolant Damage a Car?

Pure water used as a coolant can damage a car when used for prolonged periods. Water boils and freezes quickly, making the engine susceptible to overheating or freezing. Such extreme temperatures will eventually damage your engine and radiator. 

Reasons Your Coolant Is Low

Leaks are the most common culprit for low coolant. You can easily spot these external leaks and resolve them. They can occur at the radiator, the water pump, or the thermostat. 

A close-up of a car's manifold

Your coolant can also leak from a faulty manifold gasket or a head gasket. If any of these gaskets get spoilt and leak, the coolant gets absorbed into the engine and combusts, releasing white smoke through the exhaust.

A close-up of a car's radiator cap

A faulty radiator cap can also leak coolant. Radiator caps are made in such a way as to open and release pressure when they get to a certain threshold. A faulty cap opens even when it has not reached that threshold and leaks coolant. It can present itself as white smoke from the engine.

Coolant leaking out of a car

The EGR cooler is the last culprit that can leak coolant. EGR coolers are primarily installed in European vehicles, so your vehicle might not have it. Your mechanic should diagnose and pinpoint the point of coolant loss so that if they replace it, it does not leak again. 


The engine coolant is necessary to keep your engine running smoothly as it protects the engine from overheating and damage. You should always ensure your coolant doesn’t run low, checking before any long trips that you have a sufficient amount in the reservoir. 

A can of coolant in the boot can always help you out of a sticky situation. If your coolant has run low, you would always find it handy to fill it up with coolant rather than water. If ever you need to use water, get the purest water you can find so as not to introduce impurities into the radiator.

Have you ever had a low coolant situation on the road? What did you do about it? Let us know in the comments below how you resolved it.

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