Tech Features

Engine Coolant

Engine coolant is not rocket science, but it's also not just water any more
By Vahok Hill | March 1, 2013

Photos by Vahok Hill


In the not too distant past, the coolant used in sand toy engines was simple — there was none. Basically, it was just a fan that forced air over the heads, cylinders and possibly an external oil cooler. Or, a simple free air engine as you would see on motorcycles. The majority of power plants were air-cooled. Water-cooled engines were more of an oddity than the norm. The Jeep crowd and the early water pumper slingshot type sand rails were the exception.
As the dawn of a new age started, more and more sand vehicles became liquid cooled. This came hand in hand as the “need” for more power was required, and the envelope was starting to be pushed to the edge of capacity and capability for air-cooled applications. The cars got heavier and the power levels increased, based on needs and wants. The need for a superior cooling process was required and liquid cooling was the simple answer. The simple fact is that it’s more effective to design and build a liquid-cooled engine than rely on air-cooling to do the same job. The engines can be built differently, especially when your needs require a smaller physical package for the engine and the power requirements are elevated as well.
Most vehicles use a closed cooling system, which requires you to add coolant through the overflow tank. Some tanks have an inspection window showing the coolant level. This one is on a Toyota motor and shows the coolant level and color. The color is important as it indicates the condition of the coolant, and if there is any corrosion present.
Weight advantages aside, a liquid-cooled engine is dimensionally more stable under load than the air-cooled engine. Liquid-cooling allows the engine temperatures to be kept at a more stable level and allows closer manufacturing and running tolerances. You can extract more power over a longer period of time with liquid-cooled engines versus an air-cooled engine. It is not a slam to the many air-cooled fans out there, it is just a fact. There is just so much you can do with a fan, fins and an external oil cooler. The fact that you can control engine temperatures so much closer and with a lower amount of temperature hysteresis in a liquid-cooled engine than with an air-cooled engine. You can actually control the engine temperature and it becomes a tuning tool.
water was the gold standard for engine coolant up until we reached the modern age where different metals are used to manufacture an engine. Nowadays, coolant or antifreeze has a syrupy consistency and is usually mixed in a 50/50 ratio with water to provide the correct cooling properties for the system. The red antifreeze shows what the coolant will look like when it is contaminated. This came out of a vehicle that had about 55,000 miles on the odometer. Time to change!
When we say water-cooled engine, we do not always mean “water-cooled.” In the applications used today, the engine coolant is more often than not a combination of water and additional liquids. It may be a water-based coolant or a system that uses water as just part of the coolant package. That is why liquid-cooled is a bit more accurate. Often the coolant in a modern engine is a combination of water and ethylene glycol, mixed at a 50/50 ratio and even that is not always accurate, as there are also other components of the coolant, lubricants, rust inhibitors, surfactants and other components. Albeit these other components make up a very small percentage of the whole.
Some coolant comes in a concentrated mixture, which needs to be mixed with water before it is used in the cooling system. This particular coolant and antifreeze, left, comes already mixed in the correct ratio with water. All you have to do is add it to the system and away you go. Ever heard of surfactant? These products help to improve the ability of water to adhere to the surfaces of the cooling system. Through chemically modifying the water, products such as this, right, help the water to absorb and release heat as it goes through the cooling system. It is possible through the use of surfactants to lower the coolant temperatures as the engine operates.
The addition of the ethylene glycol does several things. It prevents the coolant from freezing in weather conditions where you would experience ambient temperatures lower than 32° F. It also raises the boiling point of the fluid; which is a real positive if you are running a non-pressurized system. Or, if you are running a pressurized system you do not need to pressurize the system to as great a level to prevent the system from boiling over. And, it gives you some other benefits, as well. Let’s define the makeup of coolant a bit more, prior to going into any more about potential benefits.
The use of pure water would be a passable coolant. In fact, in the early years of the automobile it was the only component used. The issue is that you can do much better than “just” using water. Water does have some down sides; it freezes at a fairly low temp 32° F, or 0° C for all you metric thinkers. Not a good thing if you are going to expose your sand toy to sub zero conditions, either in usage or storage. If you are using water as your coolant and temperature drops below freezing bad things can happen. Water is unique, when it freezes it expands. And if it is allowed to expand in a closed container, say, your engine block; very bad things can happen.
It is not uncommon for engine blocks to crack or cause other freezing related damage due to freezing water. Cracked blocks are usually not repairable and the cost of saving some money by adding antifreeze over just using water as a coolant just does not seem worth the potential risk should you expose your engine to low temperatures. Don’t count on the freeze plugs popping out and saving your engine. Those holes that the freeze plugs cover are really for getting the sand out of the block after the casting process. Freeze plugs were just a name that was coined in the early days of development for the internal combustion engine and not all engines have freeze plugs.
Water by itself is a very corrosive compound. It will cause any iron and or steel parts that are exposed to the water in the cooling system to rust, and rust is just a bad way to change a good bolt to its elemental components. Aluminum is not a friend of water, either. The coolant needs to have other chemicals added to it to act as a rust preventative or you will just corrode your engine from the inside out. Water is not known as the universal solvent for nothing. Given enough time, it will wear out anything; the Grand Canyon comes to mind.
Antifreeze is currently a catch-all phrase for ethylene glycol, which is the most common antifreeze chemical used in the marketplace today. There are other chemicals and compounds in use as well, but ethylene glycol is the biggest player. The majority of premixed coolant/antifreezes on the market are manufactured by blending distilled water and some form of alcohol. For the past 90 or so years, ethylene glycol was the antifreeze of choice. But, in the near past there has been a slow switch to propylene glycol as it is much less toxic and more easily disposed of. But, it does have its downside; it can be corrosive, so it requires even more chemicals to be added to “protect” the various metals and plastics in your engine’s cooling system.
Antifreeze is currently a catch-all phrase for ethylene glycol, which is the most common antifreeze chemical used in the marketplace today. There are other chemicals and compounds in use as well, but ethylene glycol is the biggest player. The majority of premixed coolant/antifreezes on the market are manufactured by blending distilled water and some form of alcohol. For the past 90 or so years, ethylene glycol was the antifreeze of choice. But, in the near past there has been a slow switch to propylene glycol as it is much less toxic and more easily disposed of. But, it does have its downside; it can be corrosive, so it requires even more chemicals to be added to “protect” the various metals and plastics in your engine’s cooling system.
Aside from the temperature and corrosion benefits that a blended coolant of water and antifreeze gives you, there is also the additional lubrication that is gained by the addition of specific lubricants that are added to the antifreeze by the manufacture. This helps with water pumps and any other moving parts in the cooling system.
Something else that needs to be remembered, the 50/50 mix of antifreeze and water does not last forever. It needs to be changed every couple of years in your car and you need to be aware that even though you may not put the miles on your sand toy that you put on the daily driver in two years, you should still keep on top of the coolant in you sand toy. If when checking the coolant level, you notice a change in color to a rust colored from the normal light green or pink, you need to change the coolant. That change in color is usually caused by the byproducts of corrosion in the cooling system and the coolant is no longer protecting the metal components from corrosion.
If you are running a liquid-cooled motorcycle, you need to consult the owners’ manual to look at the suggestions for engine coolant. Some manufacturers have some unique requirements. Many of the cooling systems were designed to keep the engine cool while the vehicle is moving; just sitting still can cause some issues. The type and possibly the brand of coolant has been optimized for the application. I have seen some fairly new bikes that overheated just sitting and idling on a hot summer day. Modern motorcycles need air moving across the radiator for the cooling system to work properly.
A rather new addition to the coolant market, in the last 15 or so years, is the use of “surfactants.” These products are added to the coolant to make it “wetter.” These products are called “water wetters.” This group of products help to change the surface tension of the water. The term Hydrogen bonding is not something we usually talk about around the camp fire at night after a day charging up the hills. Water molecules are polar; they have both positive and negative ends and when these ends are linked by an electrical charge they line up. The result is water droplets. The droplets are caused by this hydrogen bonding process.
Several good things happen when you add one of the surfactants to the coolant. The first thing is that the coolant mixes more thoroughly. Not that this is a problem, but it is an added benefit. The other is that the surface tension of the coolant is reduced. How does this happen? The molecular structure of the surfactant is such that its structure is soluble in substances that are waxy or oily, and it is water soluble. Much like how soaps breakdown and suspend grease in water. This is why dishes are easier to clean with the addition of soap than they are to clean with just plain water. The big bonus for the sand people is that these molecules between the surfactants aid in lining up the coolant molecules. The surface tension of the coolant is reduced and the coolant can become more efficient at transferring heat out of the engine and into the radiator. The heat transfer improvements work as you put heat into the coolant and when you take the heat out, truly a win-win scenario. The use of the surfactants helps to prevent localized steam pockets in the engine which can very quickly elevate the temperature of the coolant to dangerous levels if left unchecked.
Did you know that coolant can be made at home with relative ease? Sure! You mix water and antifreeze in equal volumes. You can add any of many commercial surfactants to the coolant as you see a need. You can also purchase coolant already mixed in the correct proportions with water, so mixing is not required. They will cost you a bit more money, but if you are working with a very small cooling system like a motorcycle or UTV, it might be a bit easier to purchase the premixed coolant due to the small amounts of coolant required. It may be a simpler option.
The point is that coolant is not rocket science, but it is also not just water any more. It does not take constant attention, but it does merit your attention to assure continued trouble free operation. It is much easier to do some planned maintenance at home than at the dunes; the option is yours. See you at the top of the hill.

 A Few More "Tech" Stories...

King Shock Rebuild
Dealing With The Devil's Pudding
Installing CV Boot Clamps
Cylinder Sleeves - Saving Engine Blocks

Don't Miss the Next Issue. Subscribe Now!

Subscribe to Sand Sports Magazine today - The leading sand publication since 1995.
Hustlin' Race Quads
When Brett Sanderson shows up to Dumont or the sand drags, he brings a double threat in the form of these two drag bikes. Wait until you see the details and workmanship on these beautiful ATVs. Nice!

Departments
Wright Publishing, Inc.
Sand Sports Resources
Off-Road Industry News
Social Media
Extras
Contact Sand Sports
Careers
Advertise
Subscribe
Sand Sports Magazine • info@sandsports.net • 3176 Pullman, Suite 107, Costa Mesa, CA 92626-3317 • (714) 979-2560