Diagnostics of the engine cooling system: basic techniques and recommendations

The engine cooling system is designed to, so that the power unit operates in a strictly defined temperature range. In other words, not allowed as overheating, as well as too intense cooling of the motor, which does not allow the internal combustion engine to reach operating temperature.

Next we'll talk about that, how to diagnose the engine cooling system, and also why you should pay attention, if the engine does not reach operating temperature (remains cold) or overheats, there were coolant leaks (OS) etc.. d.

Diagnostics of the engine cooling system

It's not hard to guess, that the main task of the cooling system is first to ensure a quick rise to operating temperatures, after which further maintenance of this temperature and effective removal of excess heat into the atmosphere is implemented.

At the same time, it is not allowed, to keep the engine too cold, since an engine not warmed up to operating temperatures wears out faster under loads, and a severely overheated internal combustion engine can jam.

It becomes clear, that maintaining a certain operating temperature of the engine is necessary for that, so that the gaps between the parts after heating are optimal, the fuel in the cylinders burned completely, the toxicity of exhaust gases decreased, etc. d. The temperature of the coolant should normally be in the range of approx 85-90 ?WITH.

The cooling system on modern cars is a combined type solution, that is, the engine is cooled by liquid, and due to air cooling. With that in mind, that this system includes a number of elements, and a special coolant circulates in a closed circuit (antifreeze or antifreeze), malfunctions often occur during the operation of vehicles.

In practice, it is necessary to check the entire system as part of diagnostics, and not just individual items for various defects or wear. It is still important to consider, that modern cars often have very limited space under the hood.

This means, that the cooling system hoses may have bends, multiple connection points, differ in size and shape. Although the service life of hoses is quite long, even high-quality products wear out over time.

  • so, let's return to diagnostics. First of all, it is necessary to check the level and condition of the coolant in the expansion tank. It is recommended, so that the level is between the "min" and "max" marks on the warmed-up internal combustion engine. On a cold engine, it is quite permissible to reduce the level to the "minimum" mark, since after heating the motor, the level will rise as a result of the expansion of the hot coolant.

It is important to remember, underfilling of antifreeze leads to, that the engine may start to overheat, while a high level often causes coolant to squeeze out through the cap of the expansion tank.

Also turbidity of coolant, the presence of impurities, etc. d. usually indicates that, that antifreeze or antifreeze needs to be changed. Usually, coolants are designed for 2-3 years of service, then there is a loss of useful properties.

  • Let's move on. If noticeable, that the coolant level even after, as was normalized, still goes down pretty fast, the cooling system should be checked for leaks. All connections must be inspected. Usually, antifreeze flows from:
  1. expansion tank;
  2. rubber hoses;
  3. nozzles or pumps;
  4. thermostat;
  5. radiator;

The tank has a tendency to crack, its cover often becomes unusable. Also, leaks in the connection points occur in that case, if the tension clamps weaken. The cooling radiator can also be damaged mechanically, cracks appear in it, etc. d. Coolant often leaks from under the thermostat housing, leaks can also be detected in the installation area of ​​the water pump of the cooling system.

In any case, on a silenced internal combustion engine, the tightness of the cooling system is determined by supplying air to the system. Also, a device is placed instead of the radiator cover, through which the air is pumped to 100 kPa. A drop in pressure will indicate depressurization.

After detecting the location of the leak (depending on the problematic element) the corresponding nozzles are changed, the radiator is being repaired, the pump is replaced, expansion tank or its cover, thermostat or thermostat housing, etc. d.

  • Now let's imagine, that the system is airtight, the condition of the coolant is normal, antifreeze does not work, however, the thermal mode of operation of the internal combustion engine is still violated. In a similar situation, the motor may overheat, and do not reach the working temperature.

Usually such problems are related to the thermostat. Its quick check can be performed directly on the machine without removal. First, a cold diesel engine is started, then the engine should be allowed to work at XX. If the thermostat is normal, the lower radiator tank will also begin to heat up as the power plant warms up. That says it all, that when heating the coolant to 80-85 ?The thermostat works.

However, we should not forget, that the thermostat can work, but with glitches. We are talking about wedging the device. Example, after heating the coolant to the set temperature (the thermostat opens, to pass liquid from a small circle to a large one. At the same time, the opening is not complete. As a result, the nozzles of the large circle heat up, however, the engine is still prone to overheating, since the coolant cannot circulate in a large circle in full.

Problems arise in that case as well, if the thermostat does not close when cooling the coolant. This is manifested by a long warm-up of the internal combustion engine, the engine warms up, but only partially or the engine remains cold all the time. These signs indicate that, that the thermostat is open all the time, the coolant constantly circulates in a large circle through the radiator.

As in the first, and in the second case, the thermostat needs to be changed, or place the device in a hot liquid, after which measure the temperature of its opening and determine the efficiency of the element.

We also recommend reading the article about it, how to eliminate the flow of antifreeze or antifreeze from the cooling system. In this article you will learn about it, What shall I do, if antifreeze or antifreeze is flowing, the coolant level in the tank decreases, as well as how to find the cause and identify the location of the leak.

By the way, if the thermostat still turns out to be working, then the problem of overheating or underheating of the motor may lie in the problems of the fan of the cooling system or the temperature sensor (the radiator fan may not turn on, and work constantly, triggering may occur late, etc).

  • The water pump deserves special attention when diagnosing the cooling system (pump) and the state of the element. Problems with the pump are usually indicated by the following symptoms:
  1. A rapid increase in the temperature of a cold engine after starting;
  2. The appearance of extraneous noises during the operation of the internal combustion engine in the area of ​​the pump;
  3. Visible axial and radial runout of the pump shaft during rotation;
  4. The appearance of a leak through the seals of the water pump.

Usually, the noisy operation of the pump indicates that, that the water pump bearing has failed. Rapid heating of the engine is a sign of this, that if no other reasons are found, the pump may not work (there is no coolant circulation). Malfunctions can be related to both the pump drive, and with the destruction of its impeller.

Leaks in the water pump installation area will indicate that, that the seal or stuffing box has failed. Anyhow, experts recommend regularly checking the condition of the water pump drive. It is also better to immediately replace the pump with a new one in that case, if there are any problems with the water pump of the cooling system.


pay attention, that not always a decrease in the level of antifreeze or antifreeze indicates problems with the cooling system. The coolant can go directly into the cylinders in that case, if there is damage to the cylinder head gasket, cracks appeared in the head or in the block, etc. d.

In a similar situation, the engine often emits white smoke, since OR in the form of steam comes out through the release. In this case, the head or block must be removed, as part of diagnostics, the block head is pressed. Then a decision is made to repair the cylinder head or replace the element. Also, antifreeze or antifreeze can flow in that case, if there are problems with the plugs of the engine block. Leaks through the plugs will indicate the need to replace the engine plugs.

  • It should be added, that with the onset of the cold season, it is very important not only to have an OR, poured strictly according to the level, but also the density of antifreeze. Remember, if during operation it was necessary to add distilled water, the density of the solution decreases. In simple words, when the temperature drops, the liquid may freeze. Freezing often results in damage to elements of the cooling system, as well as the internal combustion engine itself.

The density of the coolant is measured with a hydrometer, if necessary, the concentration of antifreeze should be increased by topping up the concentrate. At the same time, it is strongly not recommended to mix antifreeze and antifreeze of different brands.

It is also important to remember, that OJ concentrate is a strong poison! Do not allow the substance to come into contact with the skin, in the eyes, do not take internally!

  • Let's note once again, that antifreezes or antifreezes based on ethylene glycol contain a package of active additives, which prevent the formation of corrosion, have antioxidant and anti-foaming properties. However, over time, additives are triggered and stop working.

As a result, the pump impeller is destroyed, the radiator "eats" from the inside, the channels in the BC and cylinder head are rusting. Also, the breakdown products of the coolant combined with general pollution can clog the channels of the system, disrupt the operation of the thermostat, etc. d. For this reason, the performance of the cooling system deteriorates, the resource of its constituent elements is significantly reduced. In some cases, corrosion destroys the channels of the engine cooling jacket, antifreeze or antifreeze enters the cylinders or the lubrication system.

To prevent possible consequences and avoid a number of problems, the coolant must be changed once in 2 years. This is especially true, if we are talking about Tosol. It is desirable to carry out the replacement with flushing of the cooling system. Also, today there are new generation antifreezes of the G12+ type, which are designed for 3-4 years of service.

  • If there are doubts about the efficiency of the system, and also under suspicion thermostat, etc. d., during initial diagnostics, an infrared thermometer allows you to measure the temperature of hoses and nozzles. For a quick check, it is enough to turn on the stove in the cabin, then the temperature of the inlet and outlet hoses of the heater is measured. The temperature should be almost at the same mark. If obvious deviations are visible, this may indicate the need for repair.

We also recommend reading the article about it, why engine oil gets into the tank of the engine cooling system. From this article, you will learn about the various reasons why engine oil gets into antifreeze or antifreeze.

Finally, note, that the hoses, when placed in the underhood space, must be checked for kinks. First of all, example, after replacing the nozzles, you should make sure, that the hose does not bend. It is also important, that the hose does not touch hot surfaces, did not touch the elements, moving or sharp edges.

Bends worsen the circulation of coolant, which can cause overheating under load. As for mechanical damage, moving parts can rub the hose, sharp edges cause cuts, contact with heated surfaces causes accelerated cracking of the nozzles. The result is a coolant leak, which can cause overheating of the internal combustion engine.

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