How much interesting articles written about thermostats, pumps, radiators ... But the expansion tank bothered to pay attention only in passing. But when you are desperately fighting air congestion in the winter to get the stove working in the car, or wondering why the arrow on the engine temperature gauge is desperately approaching the red border, do you think about why this happens and what is the reason ... Therefore today we will talk about what troubles are hidden in the expansion tank, and how to avoid them.
What is an expansion tank
This is a plastic container with rubber hoses, with or without a coolant level sensor, and a pressure bypass valve built into the plastic cover. It is with this most insignificant detail at first glance, like a cover with a valve, that we will deal.
Why is she needed at all? And it's all about the coolant (coolant). Engine operating temperature domestic manufacturers, as a rule, is equal to 90-95 C, and in order for the coolant not to boil while circulating in the system, its boiling point must be much higher, about 130 C. Therefore, coolants are initially created with an increased boiling point.
Also very an important factor is to maintain an increased pressure in the engine cooling system (OSD), greater than atmospheric pressure, since pressure is a necessary condition for increasing the boiling point.
Working pressure in OSD domestic cars is, as a rule, 1.0 kgf/cm2, and imported cars– about 1.5 kgf/cm2. Since the efficiency and operating temperature of imported car engines are higher and equal to approximately 100-105 C, then the pressure in the system should be greater.
“And what exactly does a cap in an expansion tank have to do with pressure?” - you ask. The most direct...
The principle of operation of the cap of the expansion tank
When the engine heats up, the coolant also heats up. At the same time, since the SOD is absolutely hermetic, excess pressure is created. All SOD begins to expand, and excess air accumulates at its highest point - the expansion tank. Further, under the influence compressed air Exhaust valve expansion tank opens and excess air escapes.
When the engine cools down, reverse process. The pressure in the system drops, and in order to avoid decompensation, that is, a decrease in the pressure level in the tank below atmospheric pressure, the inlet valve opens and sucks air into the system.
Highlights a large number of heat. At the same time, it is important to keep the temperature of the unit within the specified limits for the most efficient combustion of fuel, reducing the level of exhaust toxicity, increasing the resource, etc.
In other words, it is impossible to cool the motor as much as to allow it to overheat. To maintain the required operating temperature in the device modern engines a combined system is used, which combines liquid and air cooling.
In the device of a liquid cooling system, an important element is the expansion tank. Next, we'll talk about what an expansion tank is for, what is its main purpose, and also what malfunctions of the expansion tank of the engine cooling system are most common.
What is the purpose of and where is the expansion tank of the engine cooling system
So, it is enough to open the hood to find the indicated tank. Usually, given element always in sight so that the driver can easily control the coolant level, as well as top up if necessary. On different cars tank can be mounted to the left or right of power unit, closer to the motor shield or farther from it.
The main function of the tank is to compensate for the changing coolant volume. This effect occurs as a result of a change in the temperature of the liquid. The device of the cooling system may differ, in some cases the tank is a simple container for excess liquid, while in others it is a whole device capable of regulating the pressure in the system.
Expansion tank needed liquid system on modern internal combustion engines. The fact is that coolants (antifreeze, antifreeze) are an aqueous solution based on ethylene or propylene glycol. Such a liquid has a higher coefficient of thermal expansion compared to water.
Simply put, by pouring such a liquid into the radiator, after heating the internal combustion engine and reaching operating temperatures, the liquid will also heat up and expand. It turns out that surpluses are actually formed, there is an increase in pressure, etc.
If you turn off the engine, after the coolant cools down, the volume of liquid again decreases, and a vacuum is created in the system. This leads to the fact that through the valve in the radiator cap is sucked outside air. It is quite obvious that in this case there will be air locks, which cause a violation of heat transfer, incorrect operation of the cooling system, etc.
In order to prevent this from happening, a separate container (cooling system tank) is installed, where excess hot coolant from the radiator gets. Also, the presence of liquid in the tank avoids the creation of vacuum and the formation of air pockets, since when the volume decreases as a result of cooling, the liquid from the tank fills the voids.
Today, designers have gone even further, moving bypass valve, which used to be in the radiator cap, onto the expansion tank cap. It turns out that the release of pressure and excess antifreeze during boiling occurs through the tank lid. In other words, the tank took over the function of the top of the radiator and ceased to be a simple reservoir.
As mentioned above, the tank can be installed in different places V engine compartment, however, the place of its installation must be realized in such a way as to achieve the effect of communicating vessels. The tank and the radiator are connected by pipes.
This solution allows access for excess hot antifreeze to the expansion tank. When the coolant cools, it is also possible to compensate for the missing volume in the system by receiving fluid from the tank. This scheme eliminates the ingress of air into the radiator and the formation of air pockets in the system.
Expansion tank device
Structurally, this container is very simple. The material of manufacture is translucent plastic. Also, a sensor can be additionally built into the tank, which signals the driver about a critical decrease in the coolant level.
On top of the tank is closed with a lid, in which a valve is installed to regulate the pressure. If the pressure in the system rises, then the valve is activated.
Also on the wall of the tank there is a level indicator in the form of "minimum" and "maximum" marks, allowing you to control the liquid level. It is important to understand that on a cold engine, the level should not fall below the minimum. It is also not allowed to exceed the maximum level.
As for the tank lid with a valve, it hermetically closes the container on a cold ICE. However, when the engine starts operating temperature and the coolant is heated, in the cooling system and in the tank the pressure naturally increases.
If the pressure rise reaches an average of 120 kPa, the valve opens. When the pressure drops to an average of about 83.4 kPa, the valve closes. Such valve operation is necessary in order to avoid rupture of pipes, damage to the radiator, etc.
In parallel with this, after the engine cools down, the pressure in the system begins to drop, the coolant volume decreases and a vacuum is created. When the pressure drops, on average, below the mark of 3 kPa, the opening occurs inlet valve expansion tank for air intake. As a result, the pressure difference is leveled, and the missing volume of liquid is compensated from the tank.
Common faults
As a rule, most problems are not related to the capacity itself. Not so often there are cases when the tank itself cracks and starts to flow for no apparent reason. However, even taking into account the simple design, the cap of the expansion tank of the engine cooling system may well be the problematic part.
The valve built into the cover may fail. Also, insufficient sealing can occur due to deformation of the rubber ring. As a result of such malfunctions, the cover may begin to leak antifreeze, the system becomes airy, etc.
If the valve in the cap starts to work incorrectly, then in such a case inevitable deviations in the operation of the system internal combustion engine cooling. In addition to the formation of air pockets, this situation in some cases leads to a critical increase in pressure and rupture of the expansion tank. IN similar situation tank needs to be replaced with a new one. It is not recommended to attempt to restore a damaged container by soldering cracks.
If we talk about the cover, its damage and defects, as well as malfunctions of the valves due to clogging or exhaustion, are the reason for replacing the cover. In some cases, the cover is cleaned in an attempt to restore functionality, but this method does not always work. Given the low cost, it is better to replace the element immediately.
What is the result
As you can see, the device modern car to the engine cooling system and its correct operation increased demands are made. For this reason, a special tank is additionally used in the design for effective functioning.
You also need to know if the specified expansion tank of the engine cooling system is involved in the circuit, that it is highly desirable to fill the system with only antifreeze or antifreeze, and not water. As for breakdowns, if pressure builds up in the cooling system or air locks form, special attention must be paid to the expansion tank cap.
Violation of the valves in the cover often leads to the fact that the pipes are damaged, the thermostat fails faster, the pump suffers, the engine may overheat, etc.
Drivers know that coolant is stored in the expansion tank of the car, without which the engine will not work for a long time. On top of the expansion tank is a neck through which antifreeze is poured. So that it does not spill out when the car is moving, the neck is closed with a lid. It may seem that its device and tasks are quite simple, but this is not entirely true. bottle cap extremely important element a motor that needs to be monitored so that expensive engine components do not fail.
Table of contents:Tasks of the expansion tank cap
The operation of the engine is accompanied by heating, which is quite natural, given what processes take place in it. With the heating of the engine units, the coolant also heats up, which takes away part of the heat. An increase in the temperature of a liquid is accompanied by its expansion and an increase in pressure. Accordingly, the more the engine warms up, the more pressure occurs in the cooling system, where antifreeze or antifreeze is located. To prevent rupture of pipes, radiator, pipes and other elements of the cooling system when the pressure rises, an expansion tank cap is needed, which performs not only locking functions, but also acts as a valve.
A warm engine runs at different temperatures. For some cars, the normal indicator is 95-100 degrees Celsius, for others, the value reaches 125-130 degrees, and these figures are also not limiting. At such temperatures, the coolant expands by about 20-30%, respectively, there is a serious overpressure. It is generally accepted that the normal pressure in the cooling system of a car is at a level of 1.1-1.5 atmospheres, and if it is exceeded, problems can begin. Unpleasant situations also arise with reduced car pressure, which are manifested by the creation of a vacuum inside the system and the compression of pipes, hoses and other elements.
A well-functioning expansion tank cap eliminates the possibility of creating a high and low pressure in the system, due to which it remains at the required level.
How the expansion tank cap is arranged and works
Since the main tasks of the cover is to create required pressure in the system and retaining the coolant in it, it must fit snugly against the edges of the tank, on which it is wound.
A pressure regulating valve is built into the direct cover. It plunges into the expansion tank and performs the task of bleeding or pressurizing, depending on the need.
Note: In modern foreign cars, one physical valve is responsible for the functions of bleeding and pressurizing, while on old Russian cars there are two valves, each of which copes with its task.
As long as the pressure in the cooling system is within normal limits, the valves on the cap of the expansion tank do not work. As soon as the pressure goes beyond the limit values, they perform one function or another.
Signs of a malfunctioning expansion tank cap
It is quite difficult to identify a malfunction of the expansion tank cap, and due to problems in the operation of the valve, serious malfunctions with engine units. The following main symptoms of a malfunction can be distinguished:
- Smoke from under the hood. Most often, it appears when coolant enters a hot intake manifold. In this situation, the temperature of the motor will be at a normal level. The problem manifests itself when the valve malfunctions, which should lower the pressure when it is exceeded. It begins to release pressure earlier than peak values, which leads to a splash of antifreeze;
- Overheating of the engine with cold air from the stove. If there is such a symptom, it indicates the failure of the low pressure valve. Due to problems with it, air jams will occur in the cooling system, which will lead to engine overheating.
Also, symptoms of a malfunction of the expansion tank cap can be considered a breakdown of the clamps, rupture of pipes, a radiator and other elements of the cooling system, including the tank itself. If traces of coolant begin to appear on the connecting elements, this indicates an excess of pressure in the system and the need to replace the expansion tank cap.
How to check the expansion tank cap
Expansion tank cap check - enough complicated procedure, given that its work directly depends on pressure, which is not so easy to create. IN service centers there are pressure pumps capable of pumping the required amount of atmospheres, after which it is checked whether the valve works or not.
Concerning self check expansion tank cap, it is less accurate in terms of results, but allows you to detect a malfunction in most cases. The lid is checked as follows:
Another way to check the expansion tank cap, which can not always be applied due to different engine designs and places where the cooling system hoses run. It consists in unscrewing the cap and compressing one of the thick hoses. After that, the lid is screwed into place. The hose compression is released, and if it returns to its original shape, then there is no problem with the valve in the cap.
Many people know that the car heats up during engine operation, it is required constant cooling especially during the hot season. Absolutely every car has a cooling system. An integral part of this system is the expansion tank. It serves to ensure that excess and spent pairs go into it. Through the tank cap, you can add coolant and monitor its condition if there is no special sensor.
What is this tank
First you need to determine what an expansion tank is, and what it is like in a car. Most often it is a plastic container with hoses coming out of it. Often equipped with a sensor that shows the level of coolant. This plastic container is screwed on with a lid in which a valve is installed.
The valve is used to regulate the pressure in. The fact is that this system is completely sealed and when heated, increased pressure is created, which accumulates in the expansion tank, because it is the highest point of the entire system.
During pressure build-up, a valve installed in the lid releases excess air. When the car cools, the pressure decreases, and the same valve sucks the right amount of air into the system.
You should properly care for this cover, otherwise it will work worse.
The main functions of the tank
The main function of the reservoir is to drain excess coolant and excess pressure for storage while the engine is warming up. This happens due to the fact that during heating, the volume of liquid and pressure in the entire system increase. As the liquid heats up, it expands, the pressure increases, and begins to rise into the top point systems on the same principle as in heating system Houses.
The top point of the system, as already mentioned, is this very expansion tank. It should be noted that the liquid increases only for the time of the state heated from the engine, after it cools again after the engine stops, it will drain all into the radiator. In order not to pour the liquid, there are special marks on the body of this plastic container. You need to fill in according to the following principle. Above the maximum mark and below the minimum mark, liquid cannot be filled in, this can lead to various problems.
The second function of this device is the removal of steam, which accumulates as a result of the evaporation of the liquid. This is done by the lid, which has a special valve that, if necessary, releases and sucks in air.
There are also cooling systems in which the radiator cap is responsible for bleeding air and excess heated antifreeze or antifreeze. In such engine cooling systems, the expansion tank is not considered an important part.
Tank malfunctions and their elimination
The most basic malfunction is the leakage of this tank. There may be several reasons for this error.
- Often dripping at the junction of hoses. In order to eliminate this malfunction, you only need to replace the clamp or the entire hose. In order to replace the clamp, it will not take much effort, and this can be done even in the yard, but in the case of a hose it will be a little more difficult.
- The second reason for the leakage of fluid can be a broken tank. A hole in the tank may occur due to improper handling or impact of the body. Also, the body of the tank could be pierced in the case when the lid does not work properly and does not release air, due to which the tank expanded and cracked either along the seam or in weak point. In order to eliminate this malfunction, you need to purchase a new tank and install it. It is worth paying attention to the fact that if you solder the expansion tank, then the next time the same thing will happen to the system, only with more sad consequences.
The second malfunction is considered to be an inoperative valve in the cap, this can only be corrected by replacing it with a new one. In order to replace it does not take much effort and time, you just need to purchase new cover and screw it in place of the old one.
It is worth paying attention to the fact that this should only be done on a cooled car, otherwise you can get burned.
Summing up
After reading this article, you can learn a few lessons for yourself and not repeat the mistakes that other car owners made. The main thing to know is that new coolant should be poured only on a cooled engine, otherwise it may lead to deformation of the engine itself or the cooling system.
It is also worth constantly paying attention to the cooling system and constantly looking at the readings of the sensors, and if there are none, then often unscrew the tank cap and monitor the pressure. Proper care and constant monitoring of the performance of all vehicle components can contribute to rare visits to a car service and spare parts stores. There is no principle of communicating vessels here, so the liquid rises up.
The expansion tank has become a common part of a car from the moment it was actively used antifreeze liquids, including antifreezes and antifreezes, however, given the specifics in which it functions, such a problem as “how to glue the expansion tank” becomes relevant over time.
In order to understand this issue, you should delve a little into the specifics.
So, the basis of the liquids used by the expansion tank is aqueous solutions dihydric alcohol(ethylene glycol), their feature is an increased coefficient determined for thermal expansion (compared to water).
Given this, the liquid poured into the system undergoes expansion during engine warm-up, which leads to its extrusion out through the safety valve located in the radiator cap.
When the engine is turned off, which begins to gradually cool down, the volume of liquid decreases, which leads to a vacuum in the cooling system.
Naturally, in this case, the cover valve is activated, which leads to air being sucked into the radiator, this leads to a violation in the process of heat removal, and everyone knows what danger overheating is.
In order to get inside not air, but liquid, an additional reservoir is required, which, in fact, is the expansion tank.
It, through the use of a hose, was connected directly to filler neck in the radiator, positioning it so that the middle approximately coincides with the level of the upper edge of the radiator.
This design squeezes the excess of heated fluid into the tank, in the process of cooling the engine, it refills the system with itself, while air ingress is excluded.
By the way, due to the installation of an expansion tank, the problem associated with environmental pollution was also solved at the same time.
Returning now directly to our question of how to seal the expansion tank, it can be noted that only its replacement will save the situation.
This is explained by the fact that not a single glue is able to withstand the pressure exerted by a liquid brought to a temperature of a hundred degrees.
In addition, some car models keep the operating temperature exactly within the specified temperature, or even higher.
Accordingly, for antifreeze and antifreeze, the boiling point is determined at almost 103 ° C, while due to the tightness that characterizes the cooling system as a whole, in the process of increasing pressure in it, the liquid may not boil even at 115 ° C.
Given this, if there is a crack, then the liquid will not only begin to flow out, but also, due to depressurization, its boiling point will drop significantly.
Radiator and expansion tank repair
In this article I want to tell you what to do if a radiator or expansion tank is leaking. First you need to understand why this happened. Almost all cooling systems have pressure, it can be up to 2 atmospheres, depending on the brand of car. Excessive pressure should be relieved by the cap of the expansion tank (or radiator). If the lid is soured, then the pressure begins to rise, as a result of which the plastic cracks. and sometimes honeycombs in the radiator. In newer car models, it is almost impossible to check the expansion tank cap. the valve itself is rolled in a plastic case, and not every car service can find a special pressure gauge for checking pressure in cooling systems. Therefore, if the expansion tank (or radiator) cracked by itself (without mechanical impact) the first thing I advise is to replace the cover. It costs around $ 5, although there are not very cheap exceptions.
Now about the repair itself. The plastics from which expansion tanks and radiators are made do not react with more than one glue, so it will not be possible to glue them with high quality. If you need to eliminate the leak for a while, you can clean the crack with sandpaper, degrease it with a solvent and fill it with poxypol or close it with cold welding. If everything is done qualitatively enough for several months. The whole problem is that the plastic in the cooling system, due to temperature differences, narrows and expands. Therefore, no matter how well you glued it over time, it will still flow.
The most reliable, in my opinion, the only way to repair plastic in the cooling system is welding. Almost all expansion tanks are made of PP polypropylene or PE polyethylene. They cook very well, in my practice, not one has not dripped after repair. As a donor, it is better to take not a bumper, but something more rigid, such as fender liner. It is more difficult with radiators, they are made from pa66. It is one of the hardest and most refractory plastics. The repair of such plastic must be approached very carefully, otherwise it will have to be redone. Below there will be a video of repairing an expansion tank from pa66, these are very rare and do not differ from radiators in the complexity of the repair. As a donor, I took the case from a broken drill.
