Replacing the coolant. When to change


When and why should the coolant be changed? What are the consequences of untimely replacement, incorrectly selected or low-quality antifreeze? How to replace the coolant yourself? You will find the answers to these questions below.

Why do you need antifreeze in a car

From the name it is clear that the main task of the liquid is to cool. What exactly does the coolant have to be cooled and why?

During the operation of the engine, a huge amount of heat is released, especially during the compression stroke, when the temperature in the cylinders reaches 2500 °, without cooling, the engine would heat up and fail in a few minutes. Antifreeze also maintains the operating temperature of the engine, at which the highest efficiency and economy of the internal combustion engine is achieved. The “chiller” has a second advantage - providing the car interior with heat when the stove is turned on, due to the circulation of the cooling system through the heating. So, antifreeze:

  • cools;
  • maintains the optimum temperature of the motor;
  • protects against overheating.

The principle of operation of the coolant is simple: the engine has channels called a cooling jacket. When the operating temperature is reached, the thermostat opens, and the water pump under pressure supplies liquid to the engine, after which it heats up and passes through the radiator, and again enters the internal combustion engine already cooled. In addition to the main function, antifreeze provides anti-corrosion properties, eliminates the formation of scale, has lubricating properties that are necessary for high-quality and long-term operation of the thermostat and pump.

Types and differences of coolants

Replacing the coolant. When to change

Today there are three types of coolant, each of which differs in characteristics, color, service life and composition:

  • G11 - traditional antifreeze, which is widely used in domestic cars, as well as foreign cars, where the engine is designed for low loads, and its operating temperature barely exceeds 90 degrees. G11 contains silicates and other substances in the form of inorganic additives. Their peculiarity is that such antifreeze provides a dense film on the surface of cooling parts that protects against corrosion. If the coolant is untimely replaced, the film loses its properties, turns into a sediment, which reduces the throughput of the system, clogging the channels. It is recommended to change the coolant every 2 years or every 70 km, the same regulation applies to the TOSOL brand, which has similar properties;
  • G12 - this is the name of the coolant, which is produced using the technology of organic acids (carboxylic acids). Such antifreeze has better thermal conductivity, but does not provide a protective film like G11. Here, corrosion inhibitors work in a point, when it occurs, they are sent to the hot spots, preventing the spread of rust. Over time, the cooling and anti-corrosion properties are lost, respectively, the liquid changes color, therefore, the regulation for the use of G12 is established for no more than 5 years or 25 00 000 km. The regulation also applies to antifreeze (G12) + and carboxylate (G12 ++);
  • G13 - the latest generation in the world of coolants, referred to as lobrid. It differs from other brands of antifreeze in that the basis of the composition here is propylene glycol (the rest have ethylene glycol). This means that the G13 is more environmentally friendly and of better quality. The main advantages of such a fluid are the ability to maintain the operating temperature of highly loaded modern engines, while the service life varies from 5 to 10 years, even considered “eternal” - for the entire service life.

When changing the antifreeze in the engine

Replacing the coolant. When to change

Each machine has its own regulations indicating the type of coolant and the replacement period. By adhering to the factory recommendations, filling the desired antifreeze, you will be able to extend the life of the cooling system parts, as well as ensure fuel efficiency. In addition to the regulations, there are extraordinary cases when it is extremely necessary to change the coolant.

Engine overheating

In the case when there is confidence in the operation of the water pump, thermostat, radiator and expansion tank cap with a steam-air valve, but the engine overheats, the reason lies in the coolant. There are several reasons why the coolant does not cope with cooling:

  • the service life of antifreeze is out, it does not provide lubricating and heat-conducting properties;
  • quality of antifreeze or antifreeze;
  • incorrect proportion of distilled water with antifreeze concentrate (more water);
  • insufficient amount of coolant in the system.

Any of the above reasons leads to overheating, which means that the power and economy of the engine decreases, and the risk of failure of the power unit increases several times with each degree gained.

Engine does not reach operating temperature

The reason lies in the wrong proportion of water to antifreeze. Often, car owners mistakenly pour pure concentrate into a system that retains its properties and does not freeze at -80 °. In this case, the engine will not be able to heat up to operating temperature; in addition, there is a risk of damaging the surfaces of the cooling system parts.

Each package with a concentrate has a table of proportions, for example: the concentrate does not freeze at -80 °, with a ratio of 1: 1 with distilled water, this threshold decreases from -40 °. It is important to take into account the region of operation of the car, if in winter the temperature rarely drops below -30 °, then for your own calming, you can mix liquids 1: 1. Also, ready-made “coolers” are sold to prevent such mistakes.

If you accidentally poured a clean concentrate, then you need to drain half into a container for the next replacement, and add the same amount of water. For reliability, use a hydrometer that shows the freezing point of the coolant.


An unpleasant process that destroys not only the parts of the cooling system, but also the engine itself. Two factors play a role in the formation of corrosion:

  • there is only water in the system, and not distilled;
  • lack of anti-corrosion additives in the "chiller".

Quite often, a similar process is observed when disassembling the engines of Soviet cars, which traveled most of their journey on water. First, scale deposits form, the next stage is corrosion, and in advanced cases it “eats through” the wall between the cooling jacket and the oil channel, as well as the cylinder liners.

If corrosion occurs, you will have to flush the system with special compounds that will help stop the destructive process, after which it is necessary to fill in a high-quality certified antifreeze.


The formation of sediment can be for several reasons:

  • the service life of the coolant has been exceeded;
  • mixing the concentrate with untreated water;
  • a punctured cylinder head gasket, due to which oil and gases enter the cooling system.

If the cause is identified, an urgent fluid replacement with flushing is required.

How often is replacement needed

Despite the regulations dictated by the car manufacturer, it is better to change the fluid more often, about 25% earlier than the expiration date. This is explained by the fact that during this time the pump changes at least once, the liquid is drained, then it is again poured into the system. During this time, the antifreeze has time to oxidize somewhat, losing its properties. Also, the replacement interval is influenced by the driving style, the region of operation, as well as the location (city mode or suburban). If the car is used more in the city, then the coolant needs to be changed more often.

How to drain the coolant

Replacing the coolant. When to change

Depending on the engine design, there are several options:

  • drain with a tap on the radiator;
  • through the valve located in the cylinder block;
  • when dismantling the lower radiator pipe.

Drain sequence:

  • warm up the engine to a temperature of 40 degrees;
  • open the cover of the expansion tank;
  • the car must be on a level surface !;
  • substitute a container of the required volume for the waste liquid, it is absolutely impossible to drain the coolant to the ground;
  • depending on the modification of the engine, we begin the process of draining the old "slurry";
  • by gravity, the liquid drains in an amount of 60-80%, to ensure complete drainage, close the expansion tank cap, start the engine and turn on the stove at full power, due to which the rest of the liquid under pressure will splash out.

Flushing the engine cooling system

Replacing the coolant. When to change

It is worth flushing the cooling system in several cases:

  • switching to another type of antifreeze or another manufacturer;
  • the engine was running on water;
  • the service life of the coolant has been exceeded;
  • a sealant has been added to the system to eliminate radiator leakage.

As a flushing, it is recommended to forget about the “old-fashioned” methods and use special formulations that contain detergents and cleaning additives. For example, there are kits for a soft 5-7 minute wash, the effectiveness of which is controversial, or a two-step cleaning kit. At the first stage, it is necessary to drain the old liquid, fill in a bottle of cleaner for the initial wash, add clean water to the minimum mark. The engine should run for about half an hour at a temperature of 90 degrees. On this, this system is cleared of scale and rust.

The second stage involves the removal of oil deposits and coolant decomposition products. It is necessary to drain the water from the primary flush and also make a new composition. The motor runs at idle speed for 30 minutes, after the waste liquid is drained, we fill the system with clean water and let it run for another 15 minutes.

The effect is the most clean cooling system, no corrosion, support of the resource included in the new antifreeze.

Replacing the coolant: step by step instructions

Replacing the coolant. When to change

To replace the coolant, we need:

  • minimal set of tools;
  • container for waste liquid;
  • new fluid in the required volume;
  • a set of flushing if necessary;
  • distilled water 5 liters for flushing;
  • hydrometer;

The replacement procedure is as follows:

  • follow the instructions on how to drain the old liquid;
  • if necessary, flush the system as indicated above;
  • draining the old fluid, checking the reliability of the connections of the cooling pipes and the tightness of the tap;
  • if you purchased a concentrate and distilled water, then the required proportion is mixed, which you check with a hydrometer. Upon reaching the desired mark on the freezing limit, proceed further;
  • open the cover of the expansion tank and fill in liquid to the maximum mark;
  • close the lid, start the engine, turn on the stove to maximum, let it run at idle and medium speed, but not allowing the temperature to rise more than 60 °;
  • open the lid and top up to the maximum mark, repeat the procedure, and when the liquid stops leaving the tank, the system is full.

When replacing the coolant, the system is air-filled; to remove air, it is required to press the upper cooling pipe with the tank or radiator cap open. You will see how air bubbles come out of the "cooler", and the absence of air will be indicated by dense pipes that are difficult to squeeze through.

Optimal proportions

Replacing the coolant. When to change

The manufacturer of coolants, namely concentrates, indicates the characteristics of the coolant in accordance with the proportion with water. How much water do you need for antifreeze? So much so that the freezing point is with a margin of 10 degrees than is possible in your area.



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