What it is and how to check it

Coolant is one of the essential liquids for the engine to function correctly. Its main task is to ensure that the mechanics always have the ideal temperature: a combustion engine usually gets hot and needs to be cooled periodically. At the same time it has an antifreeze function, so that low winter temperatures do not affect it as much.

As you can see, it is an essential element for a car with a combustion engine… and also in electric cars. Although the latter do not require lubricating oil for the mechanics, they do use cooling liquid to maintain optimal levels of engine and battery temperature.

We are going to analyze all the key aspects of coolant (also called antifreeze, although this is one of its properties). We will also see what you should check to avoid much more serious, difficult and expensive mechanical problems to solve.

What is coolant used for?

The coolant liquid prevents excessive heating of the combustion engine, so that it operates at the correct temperature and does not reduce performance. If the mechanics overheat, there is a risk of fuel self-detonation, head gasket failure or even engine seizure, possibly one of the most serious breakdowns.

Engine cooling was done by air in many vehicles, but with the evolution of engines equipped with more complex technologies, the need to lower temperatures increased and today they almost do not exist in cars with this system. The usual practice is to opt for liquid cooling to better absorb excess heat from the engine, caused in the cylinder’s combustion chamber.

These are special liquids, with properties beyond cooling or preventing freezing, as they help prevent metal corrosion, even aluminum or light metals, by preventing limescale formations that could occur with liquids such as water.

What coolant to use

When choosing the best coolant, there is no doubt: always the one recommended by the manufacturer for your vehicle. So check the car’s maintenance book to know its characteristics. The colors can determine them… but be careful, since each manufacturer follows a different color code.

Each color of coolant (usually green, orange, yellow, blue or pink) represents its level of efficiency. The freezing temperature, for example, is related to the amount of ethylene glycol (antifreeze) that it incorporates. Thus, if it has 10% ethylene glycol it can be used between -4ºC and 102ºC, 25% from -12.5ºC to 103ºC. The maximum level of ethylene glycol is 50%, so they can be used between -37ºC and 108ºC.

Ethylene glycol stands out because, in its pure state, its boiling point is about 197ºC, which is why, since the late 1930s, it has been the most common car antifreeze. It superseded ethanol, which tended to evaporate.

The only reason to choose such striking colors is to be able to quickly locate and identify a leak. They are not common, but the problems that a lack of this fluid can cause to the car are so serious that it is better to detect it as soon as possible. Remember that leaks (of any liquid) can cause an unfavorable MOT.

In any case, there are a series of guidelines that a good coolant must meet:

  • Low freezing temperature: so that the volume of liquid increases when cold (it could break the refrigeration circuit). It is expressed on the label, in degrees Celsius.
  • High boiling temperature: greater than that of the engine in operation, so that when it performs its function it retains properties and does not evaporate.
  • Anticorrosive and antifouling properties: which prevents solid deposits from forming and calcium buildup. The label indicates the pH (corrosion capacity of the liquid on metals), the amount of alkaline inhibitors and the maximum amount of residue.
  • Low viscosity: so that it can flow easily. It is expressed in gr/cm2.
  • Anti cavitation: that it forms little foam (they can clog the circuit). The label indicates the time it takes for the foam to disappear, less than 5 seconds and having a maximum volume of 50 ml.
  • Storage stability: the maximum time it can (minimum one year in the original packaging between –18 ºC and +50ºC).

Types of coolant

There are various types of refrigerant, called G11, G12, G12+, G12++ and G13. There are no better or worse ones, as we indicated, each one is indicated for a specific vehicle and the climatic conditions in which it will be driven (yes, it is possible for the same car in Almería and Moscow to have different coolants). We can divide coolant liquids into several types:

  • Organic cooling liquid: Made up of ethylene glycol (the antifreeze component) and distilled water, responsible for guaranteeing protection against corrosion. It stands out for being stable for long periods and being biodegradable (less harmful to the environment). They generate fewer solid deposits inside the cooling circuit, have low electrical conductivity and the boiling point is higher. As a general rule it is red or pink.
  • Inorganic coolant liquid: Like the previous one, it is made up of ethylene glycol, the most common antifreeze agent, but it is another product, such as silicates, that prevents corrosion. They last less and can be distinguished by their blue or green colors.
  • Hybrid coolant: They combine both, having ethylene glycol, glycerin and antifoam, anti-limescale additives and a neutralizing reserve that will protect the refrigeration circuit. They can incorporate silicates to protect aluminum parts.
  • Anticorrosive cooling liquid: Incorporates anticorrosive additives to prevent corrosion from occurring in the elements of the cooling system. It achieves a higher boiling point, avoiding overheating, freezing in winter and the formation of metal oxides.
  • Antifreeze coolant fluid: It is used for extremely cold climates, with freezing temperatures well below zero degrees.

Can I mix coolants?

Quick answer: No. The type of coolant used by the car is specified in the vehicle maintenance booklet and in the expansion tank. Always use one with the same characteristics.

In case of emergency, pay particular attention to these factors:

  • Never mix coolant fluids different origin. An organic with an inorganic or hybrid can end up forming a solid paste that clogs the circuit. Even just pouring a little to complete the level.
  • Never mix coolant liquids different color. In a pinch you can complete with one of the same color (its basic properties will be similar), although it is not ideal.
  • refrigerants G11, G12, G12+ They can only be combined with another of the same characteristics. For their part, G12++ and G13 can be combined.

Where does the coolant go?

The coolant moves through a circuit. The most visible part is the filling cup, which is usually made of transparent plastic, with a black or blue closing cap. Be careful, these are general details. If you have questions, go to your vehicle manual or ask an expert.

It is a hermetic circuit and it is unusual (not impossible) for a leak to occur. But just in case, it is best to monitor its condition from time to time.

Check the coolant level

It is a task whose greatest complexity is opening the hood of the car. Once you have done it, follow these steps:

  • Locate the filling glass (that deposit we were talking about before).
  • Since it is usually transparent, you will see through it the liquid of a striking color. There are two brands, with maximum and minimum level. It has to be found between both.
  • Be careful, the car must be in a flat surface when doing this check. Check with the cold engine to be more exact. And with the engine still hot it tends to increase the level of the circuit and exceed the maximum mark.

Fill coolant

If the coolant level is below the minimum, it may be a sign of a leak. The best thing in this case is to refill the tank and check after a while. If it persists, go to a workshop to find out why it is losing.

This is an operation that anyone can perform, being careful not to confuse the type of liquid to be added. Follow these steps:

  • Locate the filler cup cap
  • With the engine cold, open it. This is important, because with the engine still hot you can burn yourself.
  • It is a closed, watertight circuit. This means that it may be a little difficult to open, this is normal. Turn gradually so that the decompression is gradual.
  • Fill until the level is between the minimum and maximum marks. If you have a bad pulse, use a funnel.

Can I refill with water or distilled water?

If your coolant level is low you may be tempted to top it off with water:

  • Tap water: Absolutely, don’t do it. So much so that we dedicated an article specifically to this topic. As you know, it freezes at 0º degrees (it could break hoses, pump or connections) and boils at 100º, it would not fulfill either the antifreeze or cooling function. Additionally, water corrodes metal.
  • Distilled water: It is the lesser evil and, in fact, a compound of it. But be careful, because it reduces the coolant properties.

When to change the coolant?

Changing the coolant depends on each manufacturer. The usual thing is that it has to be changed every two years, or every 40,000 kilometers. It is not that the liquid will lose its antifreeze capacity, but there may be a loss of other properties, such as anticorrosive.

If a coolant spends too much time in the car, it can end up damaging components of the cooling system such as the radiator, thermostat, pump… Changing the coolant liquid, although it involves completely emptying the circuit to eliminate the remains of the old liquid, is not an expensive maintenance operation and you avoid breakdowns in the future that could be really serious and expensive.

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