Can You Put Water in the Radiator?

Can You Put Water in the Radiator

No one wants their engine to overheat. Therefore, engines have cooling systems filled with a mix of ethylene glycol antifreeze and water that is designed to remove heat from the engine. This coolant in your car is supposed to be keeping things cool. Yet, buying coolant for a leaking radiator can become expensive. Using water instead is a much cheaper option. However, should you use water instead of coolant in the radiator? That is a question many people do not know the answer to. Read on to find out if you can use water, if you should use it, and what happens when you do.

Cooling Systems

Karl Benz introduced the first water radiator in 1885, in his gas powered Motorwagen. These primitive cars used water in the radiator and coolant was added only in the cold months to prevent freezing. The radiator keeps the coolant at a low temperature when it’s hot. Benz’s mechanical radiator fan served as a cooling system for the engine in rear-wheel drive automobiles. The cooling system is designed to manage the heat that comes off the engine. Therefore, the cooling system is very important.

The automotive cooling system has several components which work together to regulate the temperatures inside and around the internal combustion engine. The system is comprised of two main parts: the liquid cooling and the air cooling parts. Both parts must depend upon air to some degree, but only one part uses liquid. Most newer models use a liquid cooling method and the liquid cooling system is more complex than the air.

Liquid Coolant

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The liquid cooling stored in the radiator is typical a type of antifreeze made of mostly ethylene glycol. The engine requires consistent flows of coolant so there are coolant passages in the engine block and also in the engine heads. The heater control valve allows the coolant to flow from the engine to the heater core. When the heater control valve is open, the warmed engine coolant can pass through to the heater core to produce hot air through the vents.

When you drive, the environment under your hood is aggressive and hot. When the car is on the move, natural air presses in and cools the engines. Yet, sometimes the natural air is not enough. When the engine really heats up, the coolant volume expands inside the hoses and the engine. The overflow of coolant collects inside the surge tank. The radiator keeps the coolant at a low temperature when the engine parts are getting hot.

A water pump circulates the coolant through the passages, which is moved around by hoses and cooled in the radiator. The coolant travels through the parts of the engine, absorbing the heat. The heated coolant travels through rubber hoses to the radiator. Natural air coming in from the grill cools the coolant as it passes through the radiator. The coolant then returns back to the engine and the process starts all over again. The cap on the radiator controls the pressure within the cooling system. A thermostat that regulates the coolant temperature.

Water vs Coolant

Newer cars operate at much higher temperatures than the older cars. When the system runs without coolant, the likelihood of damage to the cylinder heads and engine block is increased. Tap water leaves mineral deposits in the radiator which build up and cause corrosion. The radiator is less efficient and its life cycle is decreased.

Water freezes at 32 degrees and boils at around 212 degrees Fahrenheit. When you use coolant, the boiling point is 264 degrees Fahrenheit and the freezing point is -34 degrees. Coolants provide a protective coating on the radiator and can withstand higher and lower temperatures much better than water. Engine temperatures can exceed either parameter causing liquid freezing or boil. For that reason, additives are added to water to prevent the cooling from freezing or boiling in the radiator. If your engine is already overheating, it’s best to make sure there is coolant in the radiator.

When water is added to the radiator, it should be added as a 50/50 mix of water and coolant. The mixture should come up the line of the radiator neck. You should never operate a vehicle with water only in the radiator. This is because the coolant properties are better suited to deal with the many temperature issues that can plague the system. The coolant coatings prevent the corrosion caused by mineral buildups left by water.

However, many times, an engine can overheat at inopportune times. Perhaps the driver does not have access to coolant when the problem arises. Adding water can serve as a temporary solution until the right mix can be restored. After all, adding water is better than driving with nothing at all in the radiator.

Cooling System Problems

Water is much less of a defense against engine overheat, compared to coolant. Coolant system issues are a very commonly associated with engine overheat. The engine may overheat due to a lack of a proper mix of antifreeze and water, from antifreeze leaks, or the coolant not circulating. Engine overheat is often caused by problems that prevent the cooling system from managing the engine heat, and from cooling your engine when it runs hot. Most vehicles are equipped with a Low Coolant light that warns the driver that the coolant level is too low. These are the times when adding water is done because it is convenient. There are common issues that would cause the light to activate. Here are the most common reasons why you would have to add water or coolant:

Bad water pump – A damaged water pump stops the free circulation of coolant around the engine. When the water pump goes bad, the coolant is no longer circulated through the engine block. The result is always engine overheat. When the coolant is no longer being cooled down while circulating through the engine, the thermostat identifies the change. The temperature gauge on your dash moves toward hot and will remain there until the car is turned off.

Bad thermostat – While refilling the cooling system with the proper mix of antifreeze and water, air sometimes becomes trapped under the thermostat, forming pockets of steam that prevent the thermostat from opening. When the thermostat does not open properly, the coolant flow disrupts and the engine overheats. When the coolant in the radiator system becomes dirty or contaminated, the system will no longer operate properly.

Worn hoses – Coolant leaks are a very common reason why you would ever need to refill the radiator. When the engine heats up, the coolant volume expands inside the hoses. An overflow of coolant collects inside of a surge tank. The surge tank hose may have become worn out or damaged, These issues promote leaks as well as blown head gaskets and engine overheat. The coolant leaks can cause serious damage to the engine and fueling systems.

The leaks may begin in the heater core, radiator, thermostat housing, freeze plugs, or the head gasket. However, there are other things can cause and contribute to coolant leaks. The ac compressor is designed to prevent the coolant from leaking while being pressurized. When the ac compressor becomes worn, the bearings are damaged, the coolant leaks through the bearings. Look for the leaks. Look for any coolant pooling on the ground under your car.

Bad radiator cap – The radiator also keeps the coolant at a low temperature when the engine parts are getting hot. When the radiator cap is not on tight, air can enter the cooling system and coolant can escape. Many times, when the cap is damaged, worn, or it is not on tight, the radiator hose will collapse or burst because the vacuum has not been released. If the cap is damaged, replace it and then check the condition of the coolant. A pressure test of the cooling system will confirm whether the radiator cap is still doing its job and or the car may have a cooling system problem.

Checking the Coolant Level

Checking the coolant level in your car means you must remove the radiator cap. You must make sure the system has cooled down before removing the cap or you may get burned. Once the system has cooled, remove the radiator cap and check the coolant level. If more coolant is required, use the proper mix of antifreeze and water to refill the radiator. If engine overheat or leaks has been a persistent problem, have your car checked out.

You Need to Know This About Your Radiator

Most vehicle owners understand that a vehicle must be inspected and serviced from time to time, as referred to as routine maintenance. For those who don’t, the likelihood of problems that cause damage to the radiator is extremely high. If the vehicle is not inspected routinely, small problems can escalate to major problems that are much more expensive to fix. This is also true for vehicles which sit for long periods of time.

If you want to avoid radiator problems or other issues and save $100s of dollars that you’ll spend at the auto repair shop, you’ll need to service your vehicle often – you can use our mechanic-rated Auto Maintenance and Repair Manual to do this. It’s basically what mechanics use to go through your vehicle to check if there are any problems that need fixing. As soon as they notice the most minor problem, they’ll ask you to fork out some money even though it’s a problem you can fix yourself in minutes – the manual will teach you how to maintain your vehicle every few thousand miles and it’ll teach you how to fix minor problems that mechanics will ask you to pay for; saving you money in the long run.

A lot of our readers have the Auto Maintenance and Repair Manual printed on their garage wall and 92% of them haven’t visited the auto repair shop in the last year because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the workshop again.

Drive Safe

Pulling over to the side of road with steam shooting from under your hood is embarrassing and can even be scary. Waiting for everything to cool down can really be inconvenient. Yes, of course you may be saying water is a natural coolant, and besides, the coolant has water in it. Those things are true, but antifreeze stretches the freezing and boiling properties of water to accommodate the high operating temperatures under your hood. Here are some steps you can take to ensure that you are driving safe:

Carry coolant – Some engine overheat problems are hard to come back from. Now that you know that driving with water only in your radiator, if you have been having overheating problems or leaks, it’s best to be prepared. Keep a container of coolant and a funnel in your trunk. The next time your car overheats or you see steam coming from the hood, you’ll have the coolant to use instead of just water.

Check for leaks – Check for leaks under the hood. There may be a pool of liquid under your car with a tint of green. Th e coolant may have gotten so hot that it boiled over. If you cannot find and leaks, try bleeding the system. If you do leaks, take your car to the repair shop.

Get the vehicle servicedIt is not normal for a radiator to constantly need refilling. When the cooling system in the vehicle has not been serviced or flushed in a while, the old fluid sits and accumulates debris or sediment and even rust that blocks the core or grill over time. The cooling fins in the radiator corrode and coolant leaks occur. If the leaks are not addressed in a timely manner, the radiator must be replaced. You may need to get your cooling system flushed and start over with the right amount of liquids. If this the case, in order to keep your car on the road running smoothly for the long run, take your car to a repair shop and get certified professional help. They will know how to flush the system, replace the coolant, or service your cooling system. Get that coolant bubbling problem fixed and drive save.

Job Guthiri is a freelance writer with 3 years of experience writing for Motorsrun and other established automobile outlets. His focus and key interests are Tacomas and maintenance. Read our Editorial Guidlines and Fact Checking process.