Can You Use Water as Coolant? Myths vs. Reality

When coolant levels run low, water seems like an easy stand-in replacement. However, is water a suitable long-term substitute for actual antifreeze coolant?

Yes, water can be used as coolant in an emergency but as a temporary fix for overheating because the water has a lower boiling point than coolant and has less ability to absorb heat as compared to coolant. Water boils at 212°F while modern coolant formulations don’t begin boiling until around 260°F

In this article, we will examine the risks of relying solely on water as an engine coolant. We will compare the properties of water and antifreeze coolant, explore why water cannot adequately fulfill a car’s cooling needs, and discuss alternatives when traditional coolant is low.

How engine cooling system work?

In a basic engine cooling system, a water pump circulates coolant from the radiator through small passages in the engine block called jackets.

As the engine generates heat during operation, the coolant absorbs this thermal energy and transfers it to the radiator. Here, fins and airflow help dissipate the heat to the outside air before the cooled coolant returns to the engine. 

This continuous cycle maintains an optimal running temperature.

While water can circulate through this flow path, it lacks coolant’s higher boiling point which allows it to absorb more engine heat without evaporating prematurely.

Using just water means heat transfer from the engine is less efficient, raising temperatures dangerously close to the point of steam production. Without sufficient cooling, engine components could be damaged by localized overheating.

Properties of water vs antifreeze coolants

While water may seem like an inexpensive option to replace lost coolant, it cannot match antifreeze coolant’s tuned properties for automotive use. Here is a brief comparison between the properties of water and antifreeze coolant.

Temperature Range:
Water freezes at 32°F and boils at 212°F. Even mild cold or heat can cause issues. Antifreeze resists freezing to -34°F and boils over 257°F, allowing cooling at all temperatures.

Heat Transfer Ability:
Water boils away quickly in hot weather, hindering heat removal from the engine. Antifreeze’s higher boiling point lets it absorb more heat before becoming vapor, keeping temperatures safe.

Corrosion Resistance:
Water offers no cover from rust/leak-causing internal corrosion. Antifreeze protects the entire cooling system with carefully selected inhibitors.

Longevity:
Antifreeze coolant lasts 3-5 years with proper maintenance. Water provides inferior long-term protection and would need frequent refills.

Also Read: 6 Best Antifreeze for Older Cars

Why does coolant have a wider temperature range compared to water?

The main reason coolant can operate at temperatures beyond water’s freezing and boiling points is due to its glycol base. Glycol, specifically ethylene glycol or propylene glycol, is a thermostat liquid that does not freeze or boil at the same temperatures as water alone.

Glycol lowers the freezing point through hydrogen bonding between its hydroxyl groups and water molecules. This bonding interference disrupts the crystal lattice formation that normally occurs when water freezes. Less energy is then needed to overcome attractions and allow the liquid to solidify.

Reasons why water alone is a poor vehicle coolant substitute

Here are some of the key reasons why water alone is a poor substitute for antifreeze-based coolant in vehicle engines:

Inability to prevent freezing

Water freezes at 32°F, potentially cracking the engine block and radiator if temperatures dip low enough. Antifreeze coolant has a much lower freezing point.

Lack of adequate heat transfer

Water’s lower boiling point of 212°F means it won’t absorb as much engine heat before turning to steam. This compromises the cooling system’s ability to regulate temperatures.

Accelerated corrosion

Water does not protect against rust and electrolysis inside the cooling system. Over time, this can cause leaks from corroded parts.

Temperature fluctuation issues

As weather changes, a water-filled cooling system will be at risk of freezing or boiling outside the ideal temperature window for engine operation.

Shorter replacement intervals

Water needs more frequent draining, flushing, and refilling as it does not last as long in the system before breaking down compared to antifreeze coolant.

Lack of additives

Antifreeze formulations contain important additives that lower pH, prevent foaming, and protect metals from corroding – properties water does not replicate.

What alternatives can be used as coolant if traditional coolant is unavailable?

If you are away from your home or mechanic shop and your car coolant gets leaked and you have no coolant reserved in your car then here are some potential alternative coolant options if traditional antifreeze is unavailable:

1. Distilled water

This can be used short-term in an emergency until proper coolant is obtained. Must be changed ASAP to prevent freezing or overheating.

2. Propylene glycol 

It is commonly found in food/cosmetics. You can use it if pure food-grade propylene glycol is obtained, but its cooling abilities are not as good as automotive coolants.

3. Glycerin

Organic compound used in soaps/candles. Lowers freezing point if diluted with water, but lacks other coolant additives.

4. Windshield washer fluid 

May contain antifreeze but formulas vary – check ingredients. Dilute heavily with water due to different concentrations.

What are some common types of antifreeze coolant that are recommended for vehicle engines?

Here are some of the most common types of antifreeze coolant recommended for vehicle engines:

Ethylene Glycol

The most widely used coolant, it has good freeze and boil protection. It is often labeled as “green” antifreeze.

Propylene Glycol

Becoming more popular due to being less toxic if ingested. Has similar properties to ethylene glycol. Labeled as “yellow” or “red” antifreeze. It is also used in oat coolants. 

Hybrid Organic Acid Technology (HOAT)

Offers superior corrosion protection. May last even longer than conventional coolants. The color of coolants is yellow or orange.

How to prevent engine damage by using water as coolant?

Here are some tips for preventing water-related engine damage when using water as a coolant:

• Check coolant frequently for signs of rust or corrosion building up in the system. This is more likely to occur with plain water versus antifreeze.
  
• Consider adding a rust inhibitor additive to the water to help protect the engine from internal corrosion. Follow package instructions carefully.
  
• Monitor coolant temperature closely. Pure water has a lower boiling point and may not keep temperatures as stable as antifreeze.
  
• Replace water more often, like every 3-6 months, to prevent buildup of mineral deposits from hard water. Antifreeze can last longer.
  
• Only use distilled or deionized water which has had mineral ions removed to help inhibit corrosion. Tap water leaves minerals behind.
  
• In winter, check antifreeze protection with a tester. Consider draining the system if below -15°F to avoid freezing damage.
  
• Watch for coolant leaks which can be accelerated by internal corrosion compared to antifreeze’s rust prevention.
  
• Inspect hoses, clamps, and other components more often for cracks or corrosion weak spots when using plain water.
  
• Use only water specifically formulated for cooling system use if attempting water as an interim solution until proper antifreeze is obtained.
  

The best prevention is using the recommended antifreeze/coolant for the designed protections and lifespan it provides engines.

When to seek professional coolant replacement help?

Here are some signs that it may be time to seek professional help for a coolant replacement:

• If the coolant is dirty, dirty-colored, or has apparent contamination. Dirty coolant cannot cool the engine effectively.
  
• The coolant is low and needs to be refilled more than once per year. Significant coolant loss could indicate leaks.
  
• Engine overheating occurs due to the clogged radiator and cooling system appearing clear of obstruction. Coolant may not be transferring heat properly.
  
• Visual corrosion is present inside the radiator, engine blocks, or coolant pipes. Corrosion hinders heat transfer and can cause leaks over time.
  
• Coolant is more than 5 years old in a system not designed for extended-life coolant. Standard coolant begins to break down after 5 years.
  

Can you use water as coolant in a diesel?

No, it is not recommended to use plain water as a coolant in a diesel engine.

The best options for diesel coolants are extended-life coolants (ELC) specially formulated for diesel engines. These provide superior corrosion protection and have a service life of 5 years/150,000 miles.

Distilled water can be used short-term in an emergency pinch, but proper coolant is recommended.

How long can I use water as coolant?

You should not use water as a long-term substitute for antifreeze coolant. However, in an emergency situation, water can be used as a coolant for just a few weeks. 

Water can be used for a very short period of 1-2 weeks without causing serious damage, as long as the engine does not overheat.

What happens if you use water instead of coolant?

Here are the disadvantages of using water as a coolant in a vehicle’s cooling system:

Cracks in Engine Block

Water has a lower freezing point than coolant and can freeze inside the engine block in cold weather, potentially cracking it.

Engine Overheating

Water boils at a lower temperature than coolant, so it may not adequately dissipate engine heat on hot days and can lead to overheating.

Corrosion

Water does not have rust inhibitors like coolant does. It can corrode and degrade the metal radiator, engine blocks, hoses, etc. over time.

Mineral deposits in the radiator 

Minerals in hard water can form scale deposits inside the cooling system, reducing heat transfer abilities.

Water Leaks from seals

Corrosion from water use can weaken components and seals over time, potentially leading to leaks.

Engine damage

Overheating from less effective cooling could warp cylinder heads or crack engine blocks in severe, untreated cases.

Can you use water instead of coolant in the summer?

No, you should not use water instead of coolant in your vehicle even during the summer. While water may seem like it effectively cools the engine on hot days, coolant provides important benefits over just water that help protect your vehicle all year long.

Coolant has additives that raise its boiling point, ensuring it doesn’t vaporize prematurely on extremely hot summer days. Water alone boils at a much lower temperature and you will notice the engine is overheating in a few days.

Can I use bottled water for coolant?

You can use bottled or distilled water in the radiator but as a temporary alternative to coolant or antifreeze. If you use regular water in the radiator system, it will block the engine as water is corrosive and contains minerals that can leave deposits.

Can I use water as a coolant in winter?

No, it is not advisable to use plain water as a coolant in the winter months. While water may be a cheaper alternative, it does not provide adequate protection against freezing compared to an antifreeze/coolant mixture.

Water freezes at 32°F, which is too high a temperature. Even short periods below freezing can cause water in the cooling system to freeze and potentially crack the engine block or radiator.

Can I use water as coolant in a dirt bike?

No, it is not good to use water as a coolant in a dirt bike as there is a risk of the water freezing inside the engine if it drops below 32 degrees Fahrenheit.

Dirt bike engines work hard and generate a lot of heat. Water has a lower boiling point than proper coolant and risks boiling over, leaving the engine unprotected.

Conclusion

Water may seem like a cheaper alternative to automotive antifreeze, but it does not provide the year-round protection your car’s cooling system requires.

Coolant is specially formulated with corrosion inhibitors, sealing additives, and a higher boiling point to keep your engine performing at its best no matter the weather or driving conditions.

Avoid potentially costly repairs down the road by choosing the right product for your car’s needs. Overheating or freezing damage from using water could easily exceed any small savings from occasional fluid changes.