With what and how to flush the engine cooling system

Advice from experienced car owners than to flush the engine cooling system from rust and scale


Flushing the engine cooling system is a mandatory procedure for every motorist. Scale, dirt, rust left inside will eventually clog radiator ducts, the pump, the sockets.

To prevent this, it is important to determine the moment when the structure needs cleaning and choose a suitable remedy. Both folk and special cleaners are used to remove deposits.

This article will tell you what to flush the engine cooling system from rust and scale at home.

When is flushing necessary?

It is recommended to perform internal cleaning at least once a year. It is best to do it after the end of winter. The light indicator with the image of the radiator helps to determine the exact time. In addition, there are other signs by which you can judge the need for cleaning.

These include:


  1. Systematic engine overheating and failure to start the engine.
  2. Rheostat inertia, sluggish response to its signal.
  3. High temperature readings on the coolant sensor.
  4. Intermittent pump operation, signaling a problem in the system.
  5. Changes in the hue and odor of the refrigerant in the expansion tank.

What do I need to know before the procedure?

Flushing the cooling system is a serious procedure that requires car maintenance skills. Improperly performed cleaning can turn into problems, so before starting the procedure, you need to become familiar not only with the mechanism, but also with the rules of cleaning.

The cooling system includes parts made of different materials. They differ in their resistance to chemical reagents. Ignoring this fact can lead to the corrosion of some components and cause even more serious consequences.

For example, if the condenser of the conditioner is made of aluminum, the application of citric acid can cause its walls to thin. At the same time the cast-iron and steel parts keep their integrity completely.

The design of the cooling system should also be taken into consideration. Thin channels can be damaged if during cleaning fragments of a thick film of old toluene, pieces of rust or scale are torn off. If the channel is clogged, engine overheating will begin.

To avoid the problems that arise from radical cleaning, it is recommended to carry out prevention, use the original composition of antifreeze and change it in time.

Remedies for use at home

With competent care and compliance with the preventive regime, cleaning the cooling system is not difficult. Before starting the procedure, it is necessary to prepare it:


  1. The engine is cooled, if it was running before.
  2. A container for the old antifreeze is placed under the drain.
  3. Unscrew the plugs from the bottom of the radiator and cylinders.
  4. Wait until the fluid is completely drained from the system.
  5. The drain plugs are screwed back in.
  6. Fill the expansion tank with cleaner.
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Distilled water

If the car has been kept in order for the last few years, maintenance flushes have been carried out, then the use of distilled water is considered sufficient.

It is poured into an empty expansion tank . The amount of distillate must correspond to the volume of the tank. After that start the engine for 10-25 minutes.

For better effect it is recommended to make test drive. After switching off the car wait for time for cooling and drain water from the tank.

If the poured out distillate contains flakes or rusty sediment, cleaning is repeated. When the poured out water shows that there are no impurities, pour in fresh coolant.

Citric Acid


This remedy helps to cope with a small degree of contamination. To prepare a working solution, citric acid is dissolved in water .

The standard proportion is 30-40 g per 1 liter. To enhance the effect prepare a more concentrated solution, increasing the dose of powder to 80-100 g. Optimal pH value of the lemon reagent is 3.

After the cleaner is poured into a tank, switch on the engine and warm it up for 15-25 minutes. Leave the reagent in the system for 5-12 hours. When draining the solution visually check the degree of contamination. If necessary this cleaning procedure is repeated.

To learn more about the use of citric acid in the fight against rust, click here.

On how to flush the cooling system with citric acid, a video will tell you:


For washing take vinegar, which has a concentration of 9% . For 5 liters of water you need a glass of acid (250 ml). This cleaner is used by analogy with citric acid.

Vinegar reagent is poured into a container, from which the antifreeze has been previously drained. Fill the tank with the prepared solution, start the engine for 20-30 minutes. Vinegar liquid is drained after 8-12 hours. Flush the system with distillate and fill in with new coolant.

You can learn more about the use of vinegar in the fight against rust from this article.

Milk whey

For the work use store or home whey . In the latter case, the liquid must be filtered through several layers of gauze, so that no curd inclusions remain in it. Whey is not diluted with water before use.

Pour the liquid into the system, start the engine for 30-40 minutes and make a test run, preferably without stopping. For removal of traces of serum after its pouring out the tank is filled with distilled water and the car is started again.


Washing solution is prepared from calcined (8-10%) and caustic soda (3%).

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Powder is diluted with water, its amount in solution should be 85-90%. After filling the tank with the soda reagent the vehicle is driven 50-100 km. Then the cleaner is drained and the distillate is run through several times.

Soda solution should not be left in the cooling system for a long time. The maximum time is 24 hours.

The drink contains orthophosphoric acid, which dissolves deposits of salts and rust. However, the method is not considered the safest, as the acid has a negative effect on rubber spigots, and sugar – on metal surfaces.

If the choice does settle on this cleaner, then first the carbon dioxide is removed from the drink. After pouring, the engine is left running for a maximum of 15-20 minutes. After removing the Coca-Cola, the system is cleaned with distilled water. Read more about the use of Coca-Cola against rust here.

Specialty Compounds

Prepared chemical cleaners are divided into four groups:

  • neutral,
  • acidic,
  • alkaline,
  • combined.

To choose the right liquid, you need to determine the degree of contamination of the cooling structure and the type of deposits.

For preventive treatment, neutral compositions are purchased. Acidic agents are suitable for the removal of inorganic impurities. Organics are removed with alkalis. Two-component ones are used as universal remedies for all kinds of contaminants.

The line of effective chemical washes includes:


  1. LAVR. Russian-made foam raskoksovka is designed for trucks and cars. For flushing purposes, first pour the liquid from the bottle #1 and water. Start the engine for a quarter of an hour. Drain the first reagent and pour the liquid from the bottle No. 2, adding water. Once again leave the car with the engine running for 15-20 minutes. Flush the system two or three times with distillate. A set consisting of two bottles costs on average 500 rubles.
  2. Hi-Gear Radiator Flush . The remedy, which is produced in the United States. It is suitable for passenger car brands. The formula contains no acids, so the cleaner is safe for rubber elements.

The product is poured into the tank when the engine is cold, having previously mixed the entire volume of the bottle with 4-5 liters of water. Start the engine for 7 minutes at rpm 1500-2500 rpm.


When cleaning the cooling system, it is recommended to follow the instructions supplied with the selected cleaner. It is also useful to remember some important points:

  • After cleaning, the system is thoroughly rinsed with distilled water;
  • If the system is heavily contaminated with rust and scale, the cleaning should be repeated;
  • If the cleaner is poured into a still warm system, it must also be warm;
  • When selecting a chemical, the area of application should be considered.

The cooling system should not be filled with household chemicals designed to remove limescale and grease on plumbing fixtures and utensils.

All the most useful and important information about the ways and methods of removing rust from a car – here.


Both folk and special rust and scale remedies help to flush the engine cooling system.

To reduce the frequency of cleaning, it is recommended to change the refrigerant in the system in a timely manner and carry out preventive measures. In this case, the cooling system will work properly and will not create problems with engine overheating.

Flushing the engine cooling system yourself

The internal combustion engine needs timely cooling. If something is wrong with the cooling system, the car will not have long to drive. That is why the driver is obliged to monitor the condition of this system and flush it periodically. Is it possible to do it yourself? Yes. Let’s figure out how to do it.

Why do you need to flush the cooling system?

The main element of the cooling system is the radiator. Several hoses are connected to it. Through them, the antifreeze flows into the engine jacket, which is a set of small channels. By circulating through them, the antifreeze takes the heat away from the rubbing parts of the engine and returns to the radiator, where it gradually cools down.

Result of the coolant system flushing

If the antifreeze circulation is interrupted, the engine overheats and seizes up. An overhaul will be required to correct such a breakdown. Timely flushing of the cooling system allows to avoid violation of antifreeze circulation and protects the engine from overheating. Flushing of the system is recommended every 2,000 km.

Why is the cooling system dirty

Here are the most common causes of contamination of the cooling system:

  • scale. Antifreeze circulating in the engine heats up to very high temperatures. Sometimes it even boils. When this happens, a layer of scale appears on the walls of the radiator tubes, which becomes thicker every year and eventually begins to interfere with the normal circulation of the coolant;
  • Poor quality antifreeze. About half of the coolants on the shelves today are fakes. More often counterfeited antifreeze of well-known brands, and only an expert can distinguish the fake. Fake antifreeze contains a lot of foreign impurities, clogging the cooling system;
  • antifreeze aging. Even the high-quality coolant may exhaust its resource. With time it accumulates the smallest particles of metal from rubbing parts of the engine, which leads to changes in its chemical composition. After that it can no longer effectively remove heat from the engine. The only solution is to replace it, having previously flushed the system;
  • breach of tightness. As mentioned above, there are a lot of hoses and pipes in the cooling system. Over time, the hoses can crack or burst in the cold. The steel tubing in the radiator is often corroded. As a result, the tightness of the system is violated, and through the cracks in it gets dirt, which changes the chemical properties of antifreeze and interferes with its circulation.

General scheme of flushing the engine cooling system

The scheme of flushing the cooling system is always the same. The only differences are in the used flushing compositions and the time of their effect on the system.

  1. The car starts and runs for 5-10 minutes. Then the engine is allowed to cool down for 20-30 minutes.
  2. The drainage hole is opened, the antifreeze is poured into a substituted container. Drain the coolant only after the engine has cooled down. Otherwise you can get a serious chemical burn.
  3. The system is filled with the selected cleaning fluid. The engine is re-started and runs for 10-20 minutes (the running time depends on the selected cleaner). Then the engine is turned off, cools down, and the detergent is drained out.
  4. Distilled water is poured in its place to wash out the remaining detergent. Probably one portion of water will not be enough and the operation will have to be repeated several times until the water drained from the system is completely clean.
  5. A new batch of antifreeze is poured into the flushed system.

Citric Acid

Experienced car enthusiasts successfully flush cooling systems with ordinary citric acid.

Citric acid

It is good at dissolving rust and scale, without causing corrosion of the tubes:

  • Prepare a solution in the proportions of 1 kilogram of acid per 10-liter bucket of distilled water. If the system is not heavily contaminated, the acid content can be reduced to 900 grams;
  • the engine with acid in the cooling system runs for 15 minutes. But after it cools down, the acid is not drained out. It is left in the system for about an hour. This allows for maximum effect.


You can also wash the system with ordinary table vinegar:

  • the remedy is prepared as follows: for 10 liters of distilled water take 500 ml of vinegar;
  • This solution is poured into the system, the car is started and runs for 10 minutes;
  • engine is shut down, the vinegar solution is drained only after 24 hours.
Video: flushing the system with vinegar

Caustic soda

Caustic soda is an extremely aggressive substance that quickly corrodes the hoses in the system. Therefore, only radiators are washed with it, having previously removed them from the car. And the radiator must be copper.

Caustic soda

If it is made of aluminum, you cannot wash it with caustic soda. Here’s how it’s done:

  • solution proportions: 60 grams of soda per 1 liter of distilled water;
  • all the holes in the radiator are closed with rubber plugs, the composition is poured inside and drained after a day.

Lactic acid

The most exotic option of flushing. It is not easy to get lactic acid for an average motorist: it is not available for free sale. It comes in the form of powder 36% concentrate, from which it is necessary to get a 6% acid solution. To receive it, 1 kg of powder is dissolved in 5 liters of distilled water. The solution is poured into the system, and the driver drives the car for 7-10 km. Then the composition is drained and the system is flushed with distilled water.


Whey is not a bad alternative to lactic acid. Because it is much easier to obtain. Whey is not diluted in any way. It is simply filtered through several layers of gauze.

Whey straining

You have to strain 5 liters. Then whey is poured into a cooling system, and a driver drives 10-15 km with this “antifreeze”. After that the system is flushed.


Coca-Cola contains orthophosphoric acid, which perfectly dissolves limescale and the most persistent impurities:

    The drink is poured into the system, the engine is started and runs for 3-4 minutes, no more;

Coca-Cola flushing

Specialty Compounds

Domestic motorists generally prefer to flush the cooling system with LAVR compositions.

LAVR formulations

Firstly, you can find them in any store, and secondly, their price/quality ratio is optimal. Flushing is carried out according to the general scheme and instructions on the package of the product.

What is prohibited to flush the cooling system

Here is what is categorically not recommended to pour into the system:

  • tap water. This water contains mineral salts, which form lime scale. Any attempt to flush the system with tap water will cause even more clogging;
  • vinegar essence. Above we were talking about 9% table vinegar. But concentrated acetic acid should not be poured into the system categorically. It quickly corrodes hoses, gaskets and other rubber elements, and the system will lose its tightness.

How to avoid system contamination

The engine cooling system will get contaminated in any case. The car owner can only postpone this moment. For this purpose, it is necessary to use only qualitative antifreeze, bought in a certified store. Yes, such liquid will cost more. But it is the only way to avoid premature clogging of the system.

So, if a driver wants the engine of his car to work properly, he has to watch thoroughly the cleanliness of engine cooling system. If this is not done, the normal operation of the car can be forgotten.

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