use only water in radiator

Can you use only water without any coolant in the radiator?

In Coolant by Magnus Sellén3 Comments

use only water in radiator

The radiator plays an important role in cooling the engine of a car.

The combustion engine ignites an air-fuel mixture to move the crankshaft.

This process generates heat. Excessive engine heat can cause damage to some of the sensitive engine parts. The radiator uses a mixture of coolant, water and sometimes antifreeze to keep the engine cool.

Water in the radiator can become very hot, and it is not recommended to open the radiator cap while the engine is running.

Coolant versus only water

A few years ago, most cars only ran with water in the radiator. The engines were simple and this resulted in less overheating.

An engine that only runs with water has a higher risk of overheating and damage to the engine blocks and cylinder heads. Water also contains minerals that are deposited in the engine.

It is always recommended to use the correct mixture of antifreeze and water.

The minerals also increase the risk of corrosion in the engine parts. A coolant-water solution increases the boiling point from 212 degrees to about 265 degrees compared to when only water is used. The coolant has the important task of preventing corrosion in the engine block, but you should not use it excessively.

If you live in a cold country with freezing temperatures – your coolant-water can freeze if the mixture is not good enough, and it can cause serious damage to your engine.

How to add water to your radiator

On the dashboard of the car there is a temperature indicator that informs you when the engine overheats. Under normal conditions, the temperature gauge should be at the halfway point. If it rises, check the coolant level.

  1. Use a cloth to open a radiator cap. Most of the caps open with clockwise rotations.
  2. Open it slowly and let the pressure and steam escape from the radiator system.
  3. Check the radiator for water levels. If you cannot see any liquid, it could mean that your radiator system is leaking.
  4. The rule is to use a 50/50 mix of coolant and water. The coolant has a higher boiling point than normal tap water. It helps to keep your engine cool.
  5. If you reside in areas experiencing extremely cold temperatures you may consider adding anti-freeze to the mixture.
  6. Close the radiator cap by rotating it clockwise.
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How the car’s radiator system works


An understanding of how the radiator works is crucial when dealing with water in the radiator. The radiator transfers heat from the hot coolant through a fan. The engine becomes extremely hot and heat is transferred from the engine to the coolant and finally to the radiator.

The radiator in many cars is made of aluminum with thin fins. The radiator inlet allows the coolant to flow through the pipes and the fins dissipate the heat with the help of the fan.

Radiator fins often have a turbulator that increases the flow of hot coolant through the radiator. The turbulator helps to regulate the amount of coolant flowing through the radiator tubes. It ensures that the maximum amount of heat is removed from the coolant.

On the sides of the cooler is a tank called the transmission cooler. The main function of the transmission cooler is to remove heat from the oil. This is done by heat transfer with the coolant.

Signs of a faulty radiator

If you suspect that your radiator is damaged or defective, look for various signs. Here are the most common signs:

Leaking coolant

The moment your radiator starts to leak, you will notice drops of water under the car. You should notice this when the car comes to a standstill. You should inspect all pipes that go in and out of the radiator. Check the clamps for looseness.

In a simple radiator test, a dye is added to the water in the radiator. If the dye leaks, you will be forced to replace the cooler. Avoid touching the radiator cap while the engine is running, or stop immediately to inspect it. The radiator generates high pressure and the released steam can cause severe burns. Use a damp cloth when opening the radiator cap.

Faulty thermostat

Over time, your radiator may have problems dissipating heat from the engine. The first culprit when this happens is a faulty thermostat. The thermostat regulates the amount of coolant that reaches the engine.

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If your engine starts to overheat, you will notice that the temperature gauge on your dashboard has risen above the middle mark. If you do not fix the problem immediately, you will have more engine problems.

Low coolant

If you constantly top up the coolant in the radiator, this could mean that you have a leak in the cooling system. The coolant is indicated by a green or yellow color. Over time, sludge forms inside the radiator, which prevents the coolant from moving effectively.

Mud also prevents the coolant from effectively dissipating heat from the engine. There are other cases where the transmission radiator mixes with the coolant. This leads to the formation of sludge.

Faulty radiator cap

The radiator cap prevents the coolant inside the radiator from escaping into the atmosphere. However, there is high pressure inside the radiator and over time the radiator cap may crack. It is estimated that the radiator can withstand a pressure of 16 pounds per square inch.

It is the job of the radiator cap to control this pressure. A faulty radiator cap will cause the coolant to flow into the reservoir. This is because the coolant is released too quickly, causing the reservoir to boil over. Faulty radiator caps cause unwanted air to flow into the thermostat, radiator core and radiator hoses.

This prevents the radiator from maintaining a constant temperature, which leads to overheating of the engine. Radiator caps are relatively affordable, and you should replace a damaged cap immediately. A radiator tester can be used to test the temperatures inside the radiator.


The role that the coolant plays in cooling the engine should not be underestimated. Water is often mixed with the coolant in a 50:50 ratio; you can also add antifreeze if you live in areas with extremely cold temperatures.

The reason why water is not used alone in the radiator is that it has a low boiling point compared to the coolant. The coolant is a greenish-yellow liquid that increases the boiling point of the water. You should check the radiator system for leaks the moment you notice that the temperature gauge has risen above the center.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

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3 thoughts on “ Can you use only water without any coolant in the radiator? ”

  1. When I parked my car from driving home, I noticed some smoke coming from under my hood. However my gauge did bot show car engine was hot. Gauge was unchanged( midway as usual)

    What should I check and how?

  2. I have a Toyota Sienna 2005 model, I observed my engine gage is showing overheating, it rises above the middle line and sometimes comes down to the middle, it keeps fluctuating, I opened the engine hood to feel the temperature but it was cool, please what could be the problem and how can I go about it

  3. I have a Toyota Vitz Yaris 2010 automatic model when I driving slowly there is momentum and shaking comes like balancing in manual gear, so what should I check and how….?

  4. Due to a very high demand and high ammount of comments, you have to wait for some time for your car questions to get answered. If you want to get fast answers from a certified master technician you can ask your questions here:
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