The expansion tank cap is one of the most simple mechanisms machine, but the breakdown of which can lead to global violations of its entire well-established system.
What can break in it, because a lid and a lid, you say. But this is only at first glance. Even the most early models machines were equipped with reliable constipation made of metal. The curious dismantled them and were surprised - at first glance, the usual cap for the expansion tank contained not only a spring, but also inlet and outlet valves. Why such difficulties in order to tightly close just a coolant reservoir?
To deal with this issue, it is necessary to fully understand how the entire cooling system of a car works, and how antifreeze or antifreeze circulates in it.
The operating mode of the car engine assumes natural heating, respectively, in order to correct this heating and cool the engine, they pour into the cooling system special liquid, the boiling point of which is slightly higher than standard water (100 degrees).
So for antifreezes, a temperature of 105 degrees is typical, and for antifreezes, this threshold can sometimes be around 125 degrees. Appropriate viscosity and additional additives allow you to effectively deal with boiling.
But that is not all. Remembering the school physics course, it can be noted that any liquid substance expands when heated, which means it increases in volume. Accordingly, the pressure of this fluid on the system will increase, therefore, an additional discharge is necessary for it, otherwise there is a threat of a rush important nodes car.
But how can excess discharges be achieved when the cooling system, as you know, must be completely sealed, because the slightest ingress of air into it can lead to air locks and the circulation of the liquid will be disrupted, which will immediately affect engine cooling. It is for this question that the small inconspicuous plug of the expansion tank is responsible.
How is the expansion tank cap arranged and how does it work?
The critical red pressure mark in the cooling system provides from 1.1 to 1.5 kgf / cm2, it all depends on the model of the machine, year of manufacture and engine modification along with the cooling system. When the critical pressure limit is passed, the excess is discharged by means of a safety valve, which is located directly in the cap of the expansion tank. Such valves are also called exhaust valves. As soon as the critical parameter is eliminated and the pressure in the cooling system returns to normal, the exhaust valve closes immediately, while there is no mixture with air, since the system is completely sealed and works only with internal pressure, regulating it.
But how then does pressure build up, because when the car is at rest and cools down, the temperature of the coolant begins to drop, which means the liquid is compressed and does not create required pressure for work?
Moreover, when the coolant leaves the system, then free space remains in the expansion tank, which can be occupied by air, which, in fact, should not be there. small air locks can push out the coolant directly when starting the car. A large number of air is associated with more serious malfunctions that will require careful diagnosis and repair of failed components.
Returning to the pressure in the system, it is worth noting that when the pressure mark drops to values from 0.03 to 0.1 kgf / cm2, again, depending on the model of the car and the modification of the engines, along with other aggregate units, then the input or inlet valve cover, which begins to pump air into the expansion barrel, letting it in from the atmosphere. Upon reaching the optimum values for operation, the valve closes automatically.
How to check the operation of the cover for malfunctions?
1. Visual inspection. In order to assess the condition of the cover of the expansion barrel as a whole, it is necessary to carefully inspect it. If cracks, chips, dents, scratches are visible to the eye, then the cork must be replaced with a new one. If the top cover is covered with rust, scale and dirt, then first you should clean it and then continue the inspection.
2. Inspection of the safety valve. In order to understand how much safety valve tank lid holds pressure, it is enough to unscrew the lid when running engine, - after which a characteristic hissing sound should be heard. But what kind of pressure at that moment was in the system by eye cannot be determined, for this you need special device- a pump with a pressure gauge, which will need to be installed on the system (screwed to the fitting) and repeat the procedure.
By the way, this can be done both with the coolant drained from the tank, and with a filled tank. In the second case, it will be necessary to plug the disconnected branch pipe to the steam outlet, since it will be the pressure gauge fitting that will be installed instead.
If the pressure in the pressure in the system when pumped by the pump does not exceed 1.1 - 1.5 kgf / cm2, and the operation is accompanied by a characteristic hiss, then the safety valve has been fixed and the problem should be looked for elsewhere.
3. Relief valve— breakage of this small unit is practically excluded. The main problem in relieving excess pressure lies not in the valve, but in the tight spring of the expansion tank cap. To do this, it is recommended to carefully disassemble the mechanism and shorten the spring by at least one turn, then assemble everything again and check the operation of the lock on expansion tank.
Important feature
When disassembling the cap of the expansion tank, two springs may fly out, one small and the other large. So, do not immediately "bite" both. Spend a little more time collecting, disassembling and checking, thus you will ensure the quality of the entire system. It is often found in the recommendations that you need to shorten a large spring by one turn, and a small one by two, but all this is conditional and purely individual. Therefore, it is better to proceed in stages, spending a little more time than going to the store for a new cover.
The modern auto industry dictates its own rules in the technical component, if earlier some node was practically “invisible” (insignificant). Now, almost the performance of the entire power unit as a whole may depend on it. Ask - "what is this, for an insignificant part?" YES, at least the expansion tank cap. Moreover, on hot engines, it can be the cause of his "wedge". And most importantly, it must be checked correctly! However, everything is in order (from simple to complex), and of course, the video version at the end ...
I won’t tell you in detail now, I already have a whole detailed article about this. In this article I will try to tell you how to check it correctly.
Old motors and cork
I would like to say a few words about old engines, and why NOT the expansion tank cap. It’s just that earlier it was on the radiator (not on the tank) - it was nominal (that is, little depended on it). Often, the motors worked at atmospheric pressure, that is, the engine cooling system (ODS), did not need any pressure and sealing (no, maybe there was pressure, but not so much), and before that, water was often poured into the system, and not .
This happened because power units they used to have thick walls (often made of cast iron), worked at relatively low speeds, and if at some kind of rise (say in the mountains) your radiator started to soar, then you could just stop, wait until the car cools down and move on. The margin of safety was enormous.
New engines and cover
Now everything is completely different, as I already wrote (link above), the plug is now a valve high pressure. Which works for about from 1.1 to 1.4 ATM (it all depends on the manufacturer).
How it works? Yes, everything is simple. The expansion tank plug closes the cooling system, making it airtight. When the coolant warms up, then, according to the laws of physics, it expands, the pressure increases accordingly, and since the system is closed, here you have 1.1 - 1.4 ATM. But if the injection continues, the lid should open! IT IS IMPORTANT.
Why is this being done, in the sense of building up pressure? Again, everything is simple - in order for the coolant to boil as high as possible at high temperatures.
Now modern antifreezes can boil at 105 - 110 degrees Celsius, and if they are locked at 1.4 ATM, they will boil at 120 - 130 degrees!
BUT WHY SO MUCH? And here is a simple explanation - often modern engines, such as CHEVROLET, OPEL, BMW, MERCEDES, VOLKSWAGEN, etc., operate at high temperatures. Often at 110 degrees Celsius (CHEVROLET doesn't even have a temperature scale on dashboard so as not to shock you)!
They are called - "hot engines" , this is facilitated by both the design (for example, an increase in the compression ratio, an increase in speed, now it is not uncommon even on ATMO - 6 - 7000), and the installation of TURBINES. And in order not to overheat them, they need to be effectively cooled (this is not an ancient SOD for you), otherwise they will quickly become unusable.
Now the power units are thin-walled (they cut metal from wherever possible), TURBATED, with an increased compression ratio. And if they overheat, the head of the block can lead, or the block itself (maybe even jam the pistons), or “blow out” the head gasket
Well, what happens at the end. YES what the expansion tank cap is now part of this complex system. It should control both low pressure and high pressure (so that it does not grow unnecessarily), a little more
Cork as a regulator
There are only two types of expansion tank plug failure:
- no pressure . In a modern (hot engine), the cover MUST contribute to the injection of atmospheres (from 1.1 to 1.4). Otherwise, let's boil! Think for yourself - the motor runs at 110 degrees, but the cork does not hold, and creates atmospheric pressure in the system, the antifreeze boils very quickly, it can, at least, be thrown out of the tank. As much as possible, overheat the engine, with all the consequences.
- Excessive pressure . When the cork holds more than 1.4 ATM, for example 2.0 or even higher! It is also dangerous, you can throw off hoses and pipes from the cooling system, break radiators (and they are now made with plastic walls). This again can lead to depressurization of the system and its overheating.
Therefore, it is very important, especially for modern motors check expansion tank cap.
Verification methods
Now I will not climb into the jungle and tell you how you can check at the service station. We will use only folk methods:
- Status check . From long mileage, from water poured into the SOD, the plug can fail (yes, it corny rots - the valve rusts). First things first, you need to unscrew the cork and see its condition visually. IMPORTANT! This is done on a cold engine, because there is pressure in the system in a hot one, and you run the risk of pouring hot antifreeze over it. If the cork does not work, it “wedges” from rust, then it is better to replace it.
- Do not mix antifreeze . Especially the ones that don't mix. For example, G13 mixes only with its own kind (even if different companies). But with G11 and G12, it does not change at all, they have different additives and a base (for some). When mixing, though not immediately, a precipitate may form. You will hammer not only the plug of the expansion tank, but also the SOD.
- Do not use sealants to fix leaks . It has already been proven that they do not help well, but they clog the system STRONGLY!
AND THE MOST ACCURATE CHECK . This is to make a stand. When I worked at a service station, our VAZs often came to us, especially KALINA, VAZ 2114, 2110, etc. Their stoves often leaked, and often the problem was precisely in the plug of the expansion tank ( high blood pressure).
So, we made a simple but very effective stand, removed the expansion tank from the car. It has three entrances. Two were jammed, and the third was pressurized from a pump with a pressure gauge (usual for tires).
They screwed the plug in place. The pump was turned on and pressure was created in the tank. If it does not hold any pressure at all, IT IS NOT WORKING, you can throw it away. If it holds above 1.3 - 1.4 ATM, say 2.0 ATM, then it is also not working!
But if the pump starts to pump, it reaches 1.4 ATM, then the valve opens and excess pressure is released, hissing appears (but 1.3-1.4 ATM keeps even after you turn off the pump) - then it can be put on the machine working. THIS IS 100% VERIFIED!
Now the video version, watch
And this is where I end, I think my materials helped you. Sincerely yours AUTOBLOGGER
To be honest, none of us attach any serious importance to this device. Well, the cover - what to take from it - it is suitable only so that the coolant does not splash out! That's what 90 percent of motorists think. Although this is fundamentally not true, if this "plug" on the expansion tank of your car fails, at a minimum, the coolant will constantly splash out, and at the maximum it can provoke a series unpleasant breakdowns. So you need to know how it works and the basic principles of its device. As you guessed, today I will talk about it ...
First, a little definition
tank cover - this is a locking element that has two valves in its structure, high and low pressure. This element protects the cooling system (CO) of the car from damage, and also normalizes operation.
In fact, to call it a lid or a cork - the tongue does not turn, I would say so - this is a pressure control sensor, only with a cork on top!
Tank lid task
As you know, when the engine warms up, the coolant also heats up - it expands. Accordingly, this creates an increased pressure, which is greater than atmospheric pressure, this is natural. It should be noted that a slightly increased pressure in CO is neither bad nor good for the engine by and large- doesn't matter! The main thing is that it is enough for the functioning of the system. It must also be sealed.
If you want, it can be compared to a house heating boiler. The boiler is the engine, the pipes are pipes, there is an expansion tank here and there.
The hotter it gets, the more pressure builds up in the system. It should be noted - that many old units operate at temperatures of 90 - 95 degrees. But modern engines have great performance, so it is not uncommon to work at 100 - 110 degrees Celsius, for example, my AVEO is a high-temperature motor, its normal figure is about 115 degrees. As you understand, these are average figures, but at peaks they can reach even higher values of 120 - 125. Coolant at such temperatures can increase by 20, sometimes even by 25% - that's excess pressure for you.
In order not to break the tubes, radiators, pipes and the expansion tank itself, a special valve was invented, which is located in the lid.
normal pressure in various systems, on warm engines should be in the range from 1.1 to 1.5 (bar) atmospheres. More is dangerous.
Even if the pressure rises much higher, the cooling system can be damaged, in simple terms, just break all your hoses or even worse radiators.
This is where the cap of the expansion tank comes into play, it “bleeds” excessive pressure, bringing it to the norm, say, 1.1 atmospheres. This way, all your pipes and hoses remain unharmed.
Low pressure is also dangerous!
Just imagine - you went on business in the winter, and then you put the car on a joke (to spend the night in the parking lot), the antifreeze will begin to cool and decrease in size, that is, “settle down”. And the pressure will also begin to fall (after all, the valve threw off the excess and closed), so the decrease in pressure will begin to create a slight vacuum. Hoses and pipes will shrink inward - which is also not good.
Again, the cap of the expansion tank starts to work, it also has a low pressure valve, that is, if a vacuum begins to be created, then the system opens and replenishes with air. The hoses expand - to a normal level.
Thus, the cap of the expansion tank works both in one (high pressure) side and in the other (low). It is very smart and very desired element systems, despite their simplicity.
Very often, first of all, it saves radiators from damage (after all, they are expensive on foreign cars).
The device, the principle of operation of the tank lid
As I already pointed out from above, the task of the lid is to keep the pressure up to a certain limit. It becomes clear that it should sweaty adjoin the tank and not allow the pressure to bleed, up to a certain limit - 1.1 - 1.5 atmospheres.
The cover itself holds practically nothing, it is only needed to press the high-low pressure valve, which is immersed in the neck of the expansion tank.
As a rule, there are one or two sealing gaskets on the valve body, which act as a kind of glands. In many foreign cars, there is only one valve, it is also inlet and outlet, that is, it can bleed and build up pressure.
Worth noting for many domestic VAZ, the cover is arranged differently, there are physically two valves here, one, you guessed it, works only to relieve pressure, the other to pump it (normalize) to normal.
These valves are named:
- Safety - from high rates
- Vacuum - from low values
But while the pressure in the system is normal, both are closed - they do not work, this is the norm! However, the cover often breaks, it is very difficult for a simple motorist to determine (and it is very difficult for a beginner), although this entails quite expensive breakdowns. Now a few words about the signs of such a malfunction.
Signs of a malfunctioning expansion tank cap
Often the high pressure valve fails, it simply starts to throw off the antifreeze at a normal rate, or does not take it off at all.
- When normal pressure drops off (when the engine is warm), a splash of antifreeze or antifreeze occurs and, accordingly, its decrease. Often, steam can pour out from under the hood, because the liquid enters the hot exhaust manifold. Moreover, the engine temperature is not in the red zone, that is, it is working, which means 90% cover.
- If the vacuum valve fails, completely different signs will appear. This is how air jams often occur in the system - this leads to the following, the engine overheats, and from the stove is coming cold air.
To be honest, there can be a lot of reasons, for example, another of the signs is when the tubes break or the clamps break. YES, and the tank itself can burst - this means that the high-pressure valve does not relieve "excess" and it begins to exceed 1.5 atmospheres, by the way, it can damage the radiators themselves, let me remind you of their two main and stoves (in the cabin).
So if you have started to “snot”, connecting clamps or other connections, hoses often knock out - change the cover.
How to check the work yourself?
To be honest, this is a little problematic, the valve-cover needs to create either increased pressure or reduced pressure.
However, first you need to inspect it visually, if you notice cracks, abrasions, rupture of gaskets, or other mechanical damage, then this is most likely a cover. Also, from time to time they can become unusable and internal elements valves, some manufacturers recommend changing these plugs every two to three years, then there will be no problems.
Now a few simple ways fault definitions:
- Start the engine, warm it up, then carefully start unscrewing the cover, if a “puff” occurs, then it keeps its “atmospheres”, most likely working.
- We look at thick hoses, if they are severely deformed, as if squeezed, then the vacuum valve does not work - the cover is for replacement.
- There is another way, but it is not always possible to use it. We unscrew the lid from the tank, strongly squeeze one of the thick hoses, then, without releasing the hose, we twist the lid - if they take their original forms, then our cork is working. If not, change. The only downside is that many modern foreign cars it is rather difficult to do so.
Of course, at many stations there are special pressure pumps, to which the lids from the tank are screwed and pumped - 1.5 atmospheres, after this critical indicator is crossed, the valve should open, if this does not happen, then it is faulty.
In conclusion, I would like to say that on many foreign cars the lid breaks when unscrewed, the valve itself remains inside the tank, and does not come out of there. This suggests that the vacuum that has been created inside does not allow her to leave! A replacement is needed, not because it is broken, but because the valve is “dead”.
This is how the article turned out, for those who are lazy, we watch the video version.
This concludes, I think it was interesting, read our AUTOBLOG.
The role of the engine cooling system is difficult to overestimate. It is believed that the most important parts of this system are the pump and the radiator. But is it really so? For example, what secrets does the usual small cap on the neck of the expansion tank hide?
What is an expansion tank cap
To tell the truth, few drivers give great attention such a part of your car as the cap on the expansion tank. 90% of car owners believe that the cover acts as a locking device, that is, it simply prevents the coolant from splashing while driving. However, this is the opinion of amateurs.
The tank lid is indeed a locking device, but this is not its only function. Inside the cover there are two valves that stabilize the pressure in the cooling system and protect the engine from high temperatures.
The lid fits snugly to the edge of the tank, due to which conditions are created for the complete sealing of the cooling system
Device and functions
So, the cover in its composition contains the following elements:
housing made of hard plastic alloys;
rubberized gasket that acts as a seal;
two valves, one of which lowers the high pressure in the system, and the other raises, if necessary.
Included in lids different models cars can include from one to three springs In fact, the cap of the expansion tank is a pressure control sensor. After all, when the engine warms up, the temperature of the coolant also rises, and therefore its volume increases. The more antifreeze or antifreeze warms up, the higher the pressure in the cooling system. At peak temperatures, the amount of coolant can increase by 20% due to expansion. Of course, under such loads, both the tank itself and the pipes suitable for it can burst. To prevent this from happening, a safety valve is built into the tank lid, which gradually relieves excess pressure.
The second valve is called the vacuum valve, since its main task is to increase the pressure in the system. He works primarily in winter time year, when the car is parked overnight in open areas. During parking, the coolant cools quickly and begins to decrease in volume. Accordingly, the pressure in the system drops rapidly. When the driver starts the engine, antifreeze cannot cool it well. To stabilize the pressure of the coolant, a vacuum is installed in the reservoir cap. valve train.
If the lid has lost its tightness, it can fly out of the neck of the tank under the influence of high pressure That is, the expansion tank cap on cars works "in both directions" - it can both lower and increase pressure. Despite its apparent simplicity, the cover does the job of paramount importance and, one might say, protects the hoses and the radiator from damage.
How the coolant reservoir cap works
System internal combustion engine cooling completely sealed. However, due to the fact that the coolant is made on the basis of methyl alcohol, it can increase in volume during the heating process.
Therefore, excess liquid, as well as compressed air, enters when heated into reserve capacity- expansion tank. If the air in the system is highly compressed due to an increase in the volume of liquid, then the exhaust valve in the lid is activated: it opens slightly, and excess air comes out.
Next, when the machine for a long time stands, the reverse reaction occurs: the motor and the liquid cool down, due to which the volume of antifreeze is sharply reduced. Accordingly, air jams appear in the system. Thanks to the inlet valve, these plugs are quickly removed from the system.
The valves in the cover maintain the necessary pressure in the system How to check the operation of the valves
Self-checking the cap of the expansion tank is difficult because without a special device it is impossible to know whether there is pressure in the system or not. Therefore, in service centers use instruments equipped with a pump and a pressure gauge, which give an accurate assessment of the performance of the cover and each valve separately.
To diagnose the tank cap, a special device is used, which includes a pump and a pressure gauge However, there is an easy way to check the reservoir cap:
On a cold engine, unscrew the cap from the reservoir neck.
Inspect the product from all sides: for cracks, dents, chips, breaks.
If mechanical damage no, screw the cap back on.
With the engine running, carefully unscrew the cap.
At some point, gases should escape from under it - this indicates that the valve mechanism is in good condition.
Assess the condition of the connected hoses. If they are severely deformed, crumpled or swollen, then the pressure relief valve is definitely not working.
When checking, it is important to slowly open the cap, as the coolant can escape from the reservoir under high pressure. By completing these simple steps, you can determine whether the valves on the tank cap are working or not.
Malfunction symptoms
The failure of the high pressure valve is usually accompanied by the fact that coolant begins to be ejected from the system even at normal pressure. Or, with strong heating of the antifreeze, pressure does not bleed. The driver can notice this problem by puffs of steam from under the hood. While driving, the engine starts to warm up, the temperature of the coolant also rises. Antifreeze emissions fall on intake manifold, because of which it begins to quickly evaporate the liquid.
If the problem lies in the vacuum valve, then completely different signs of a malfunction will be observed. Air locks occur in the pipes of the cooling system, since the valve does not equalize the pressure. Because of this, failures may occur in the operation of the motor, since the low pressure of the coolant does not allow the cylinders to move correctly. In this case, the first symptom of this malfunction is hot motor and cold air from the stove at the same time.
Another symptom of a malfunction of the expansion tank cap are hose ruptures or tearing of pipe clamps. In addition, due to the destabilization of the internal pressure, all connections of the hoses and pipes of the system may fail. Therefore, at the first sign of expansion (indentation) of the hoses, you should immediately change the cap of the expansion tank on the car.
Pipe deformation is clear sign expansion tank cap failure Do-it-yourself expansion tank cap repair
Repair work on the tank lid is so simple that even a child can do it. This is due to the fact that the cover design itself is simplified to a minimum. So, in order to repair the cover and valves in it, you must perform the following steps:
Unscrew the cap from the neck of the tank.
Pry off the rubber seal inside the cover with a flat screwdriver and remove.
Under it is a small valve device - you need to pry it with a screwdriver and pull it out. Nearby is the second valve - it is pulled out following the example of the first.
After that, clean out all the dirt that has accumulated in the lid. It is best to use ordinary soap solution and cotton swabs.
Screw the cap onto the neck of the tank and check the tightness of the system after warming up the engine.
After cleaning and installing the elements, the cover must perform its functions in full What are the consequences of a defective lid
As mentioned above, the cap on the expansion tank is designed to stabilize the pressure of the coolant in the system. Accordingly, if the valve mechanism does not work, there will be no bleeding of excess pressure - this threatens to rupture both the hoses and the radiator. In rare cases, due to the high pressure of antifreeze, the tank itself gives a crack.
Low pressure in the system is dangerous because air pockets form. Because of them, the motor is not cooled to the right extent and may boil.
Therefore, the condition of the cap of the expansion tank must be checked periodically. Driving practice shows that replacing the cap every two or three years completely eliminates the occurrence of problems with the valves.
The most serious consequence of a tank cap failure is engine overheating. The driver of any car needs to know about the purpose and functions of such a small element of the cooling system as the expansion tank cap. Engine cooling jokes never end well, so better times buy in two years new cover than to install a radiator or new pipes due to breaks.
Expansion tank cap - an important spare part in the cooling system car engine but not everyone knows about it. Improper operation of the expansion tank cap can lead to rapid boiling of antifreeze or antifreeze, which causes further leakage in the cooling system. How to check the RB cap for suitability?
To make sure that the cover is intact, you first need to check it for cracks, scratches, other flaws and breakages. Visually examine it from all sides. The cover consists of 3 elements: springs, fasteners and a metal top. It is important to check the spring, it should not lose its properties. And, therefore, when compressed, it should not be easily squeezed, it plays the function of a pressure holder, in this state the spring can skip it.
If the valve in the cover is working properly, then the cooling system is maintained the right pressure, which is higher than atmospheric, so the boiling point of antifreeze is higher than it should be. Important: use antifreeze, not antifreeze.
