Engine coolant and Antifreeze

When it comes to cars, every driver knows that there is a vast number of different oils, liquids and substances required to maintain the smooth running of the vehicle. One of the most important of these keeps the engine from overheating and becoming damaged as a result.

The engine cooling system circulates liquids around the engine and allows the transfer of heat to be dissipated through heat exchangers and the radiator to maintain an optimal operational temperature.

What is car coolant?

Car coolant is the liquid that is used to remove the heat generated by the internal combustion engine. It is a compound consisting of ethylene glycol, water and various corrosion inhibitors and additives. Ethylene glycol makes up the majority of the liquid, accounting for between 90% and 95% of its composition. Coolant starts life as a clear liquid, however, to differentiate between the various coolant types, the clear liquid has dye added.

Water was the coolant of choice for engines traditionally. This continued until the introduction of ethylene glycol in the 1930s, which, ultimately, transformed the automotive industry. The higher boiling point and lower freezing point allowed cars to operate in a wider spectrum of climates and weather conditions.

During the early days of its introduction, it was not known that, when oxidisation occurs, acids can form. These acids would corrode and damage the internal working parts of the engine. In response to this fatal flaw, additives were included in liquid that would stave off these unwanted effects.

Designed to prevent the corrosion, these additives included nitrites, silicates, phosphates and borates. Unfortunately, these additives did not last and over time became less effective. This resulted in the coolant requiring regular periodic change so that it could maintain its effectiveness and refrain from oxidising.

Benefits of engine coolant

There are many different benefits of using engine coolant in your car, some of these include:

• Reduces temperatures by transferring heat away from the engine. This prevents overheating and provides operational temperatures of up to 129 degrees Celsius.
• Reduces the freezing point of the liquid to around -37 degrees Celsius. This can be lowered further with specific mixtures. This prevents the engine block from failing at extreme temperatures.
• Reduces the amount of engine wear by the inclusion of corrosion preventing additives. Prevents rust and cavitation within the cooling system of the engine.
• Provides lubrication to the moving parts within the water pump. It also prevents wear to the other rubber and plastic parts.

The cooling system of the car reduces the risk of damage to the engine through heat exchange. The engine coolant temperature sensor monitors the temperature of the coolant. The driver can see this information from the dashboard warning lights or temperature gauge.

Is antifreeze the same as coolant?

Although these two liquids are often referred to synonymously, there are differences between them. The differences regard the composition of the substance. Both liquids use glycol as a base. However, coolant will typically dilute glycol ethylene with water and antifreeze is an undiluted glycol. When antifreeze is diluted, it becomes coolant.

The application of the liquids also differs. Engine coolant raises the boiling point while lowering the freezing point. It doesn’t only help prevent overheating, it also reduces rust and corrosion. This adds longevity to the car engine. It achieves this by the inclusion of corrosion inhibitors.

These are from the antifreeze element of the substance. These chemically bind themselves to the metal within the cooling system of the car, forming a protective layer over the system that staves off corrosion.

Most types of antifreeze added to the cooling system of an engine are mixed with water to create engine coolant. This is usually a 50/50 mix. You should always check the specification of your vehicle when adding antifreeze to the cooling system. There are several different types designed for use in different engine types. Originally, they could originally be differentiated by their colour.

How does engine coolant work?

Car coolant works by circulating around the cooling system of the engine, acting as a heat transfer medium. It removes the heat from the engine block and dissipates the heat through the radiator. It achieves this by absorbing the heat generated during the combustion process. Facilitated by a water pump, the circulation of the coolant liquid is connected to and is powered by the engine itself.

Engine coolants range from straight water to chemical compounds. They reduce the freezing temperature of the liquid and, at the same time, raise the boiling point. They are an antifreeze and water mix. If the coolant freezes, it can crack the engine block or warp the head. If the coolant gets too hot and cannot dissipate, the residual heat and the pressure can increase within the engine and blow a gasket. It can also potentially warp the head.

Damage like this is significant and, in some cases, the repairs may cost more than the value of the car. Engine coolant also protects the engine by providing lubrication. This protects the cylinder, water pump, head gasket and piston timing.

Antifreeze colours

There are various colours available. These consist of: yellow, green, blue, orange, pink, violet, and red. It’s always recommended to check your vehicle documentation or speak to a car servicing expert. This is because different engines require different antifreeze types depending on what materials the engine is constructed of.

You should not mix different coolants. The additives and inhibitors may be incompatible and can cause corrosion within the cooling system. If the coolant is being changed, it may be worth flushing the coolant system before refilling. As always, you can visit your local Arnold Clark service centre if you need help refilling your antifreeze.

Best ratio for coolant

The ratio of antifreeze to water will change the operational efficiency of the coolant. This can inform you when deciding on how much coolant to add to your cooling system. If you do not want to worry about the ratios, there are premixed coolants available.

Different types of coolants

Below are the various types of car engine coolants, their usage and life span.

Inorganic Additive Technology – ‘IAT’

These phosphate-silicate coolants were the first chemical coolants used in the automotive industry. Considered the ‘traditional’ engine coolant, they are designed to protect the following materials:

• Cast iron
• Brass
• Copper
• Aluminium

This coolant is less frequently used in modern cars. This is due to the evolution of material and technology used within the engine. IATs last 2-3 years and up to between 44-45,000 miles.

Organic Acid Technology – ‘OAT’

Utilising organic acids and corrosion inhibitors, OAT coolants fixed some of the issue of IATs. OATs last longer than their non-organic counterpart. They have a five-year lifespan or just under 150,000 miles. A defining difference of an OAT coolant compared to its traditional counterpart is that is doesn’t protect copper and brass. If operating a diesel engine, a nitrate-free OAT might be necessary. OAT coolant has been used by Volkswagen, Audi, Saab, Honda as well as GM and Dodge/Chrysler.

Hybrid OAT – ‘HOAT’

The organic acids found in OAT and the silicate inhibitor from IATs are combined in a HOAT coolant. This makes them a great choice for aluminium engines and cooling systems. These coolants can last for up to ten years and 180,000 miles.

Phosphated HOAT – ‘P-HOAT’

These phosphate hybrid OAT coolants are prevalent among Asian manufacturers. These include Hyundai, Nissan, KIA, Toyota, Subaru and Honda. Like an OAT, they can last five years and 150,000 miles.

Silicate Hybrid Organic Acid Technology – ‘SI-OAT’

Used by Mercedes-Benz, Porsche, Audi, Volkswagen and other European manufacturers, silicate HOAT coolant provides five years or 155,000 miles of protection for the average passenger car. These numbers change when used in heavy vehicles with the coolant requiring changing every three years or 310,000 miles.

NAP-Free HOAT

Free from nitrites, amines, phosphates, or silicates, these coolants are ideal for heavy diesel engines. They have an impressive life span with up to ten years of use, which equates to 1 million miles or 20,000 hours. BMW, Tesla, Volvo and MINI have all recommended NAP-free HOAT coolants.

Nitrate OAT – ‘NOAT’

Another type of coolant that has heavy-duty diesel applications is NOAT coolants – these include nitrates and inhibitors as part of their organic acid technology and last up to just shy of 60,000 miles or 12,000 hours of run time.

Can you mix antifreeze colours?

Due to the different chemical makeup of the varying antifreeze types, mixing is not advised. This can result in adverse and unwanted effects.

How to check and top up engine coolant

1. Step 1

   To top up the coolant in your car’s engine, you must first ensure that there is no heat in the engine block prior to opening the coolant cap. This is because the cooling system runs under pressure. Attempting to remove the cap when the engine is still warm can result in burns from pressured coolant and steam erupting from the cap location. It is also advised that the car is parked on a level surface when attempting to check the coolant level.

2. Step 2

   You can easily top up the car coolant yourself, just make sure that the amount sits within the min and max lines indicated on the cooling system opening. This is typically indicated by an engine coolant symbol illuminating. This symbol is usually a thermometer sitting above and between two wavy lines, which signify the coolant liquid.

How to dispose of antifreeze

When the engine coolant has expired, you must dispose of it correctly. It is toxic and can have a negative environmental impact. Ethylene glycol is the main ingredient in most engine coolants. Propylene glycol is also used and, although it isn’t as toxic as ethylene glycol, it should still be treated with care. Ethylene glycol carries an ‘acute toxicity’ rating at category 3 according to the Standard UK dangerous goods emergency action codes^[1].

Small spills that may seem inconsequential can have massive implications. Ethylene glycol has a sweet taste and can be easily lapped up by pets. If your pet ingests ethylene glycol, it can cause serious poisoning. Half a teaspoon per pound (lb) of body weight can be fatal to dogs, cats and other animals. Spills must be treated seriously and should be absorbed and cleared promptly.

Antifreeze should always be disposed of correctly, it should never be poured on the ground or down the drain. Disposing of ethylene glycol in this way can allow the toxicity to enter and pollute the water supply and impact the surrounding flora and fauna. Instead, check to see whether your local council will take your spent car coolant/antifreeze at your local council recycling centre and dispose of it there.

Symptoms of ethylene glycol poisoning

There are several stages after ingestion of ethylene glycol that you should be aware of if you suspect your pet may have consumed some. It is important to act extremely quickly and look out for the following:

Typically within 30 minutes of ingestion:

• Vomiting
• Excessive thirst
• Lethargy
• Incoordination
• Excessive urination
• Hypothermia
• Seizures
• Coma

Typically between 12 and 24 hours after ingestion:

It may seem that the initial signs you first observed have improved. Regardless, you should take your pet to the vet to be safe. Dehydration and elevated heart rate and breathing could be present during this period.

Typically, between 36 and 72 hours after ingestion:

During this period there may be issues with kidney function that could manifest as your pet is unable to pass urine or only passing a little. This is the result of swollen kidneys. You will have also observed the progression of the symptoms in stage one.

If you are ever unsure as to any of the above, please reach out to your local vet or medical professional for an expert opinion.

Conclusion

In conclusion, your car cooling system circulates antifreeze/coolant around the engine to stop it from overheating and to prevent premature damage. This is integral to the smooth running and maintenance of your car. Antifreeze and coolant liquids allow for the transfer of heat to be dissipated via heat exchangers and the radiator to ensure the engine can operate at an optimal temperature.

Coolant also helps to protect the cylinder, water pump, head gasket and piston timing by providing lubrication within the engine. Be careful when refilling coolant and, as always, if you have any questions or queries about engine coolant and your engine cooling system, then the team at Arnold Clark is here to help.

References

1. https://assets.publishing.service.gov.uk/media/5d53e733e5274a42d4ab5ed3/Ethylene_glycol_incident_management_PHE_2019.pdf