Typically, the cooling system creates normal conditions for engine operation. The system coolant is stored in the expansion tank. From the state of such a detail as a cover expansion tank vaz 2114, the operation of the engine and other vehicle components often depends.
A bad cap can cause overheating and radiator failure, cooling fan and water pump failure, fan belt breaks, thermostat malfunctions, coolant leaks, and serious damage engine due to overheating.
Jpg" alt="VAZ 2114 expansion tank cap" width="670" height="400" class="lazy lazy-hidden size-full wp-image-5359" srcset="" data-srcset="https://vazremont.com/wp-content/uploads/2018/04/foto-1..jpg 300w, https://vazremont.com/wp-content/uploads/2018/04/foto-1-660x394.jpg 660w" sizes="(max-width: 670px) 100vw, 670px">!} 
Functions
The expansion tank cap has two functions:
- shut-off;
- regulating pressure.
The locking function, as with all covers, is performed to avoid splashing of the coolant and to ensure the tightness of the cooling system.
The pressure regulating function is related to pressure differences in the expansion tank and the prevention of malfunctions and malfunctions.
Device and principle of operation
Structurally, the cover is a locking element, which is equipped with two valves. The first valve is used to reduce pressure, the second - to supply atmospheric air and increase pressure in the tank. The principle of operation of the cover is associated with changes in the density of the coolant when it is heated and cooled.
When the engine starts, the antifreeze heats up and its bulk density increases to 20-25%. Hot antifreeze warms up the air space. The exhaust valve sensor is triggered, it opens, part of the air leaves the tank and the pressure returns to normal. The bleeding process is periodically repeated when the internal pressure of the system exceeds 1.1-1.5 atmospheres.
Jpg" alt="Lid device" width="600" height="312" class="lazy lazy-hidden size-full wp-image-5360" srcset="" data-srcset="https://vazremont.com/wp-content/uploads/2018/04/foto-2..jpg 300w" sizes="(max-width: 600px) 100vw, 600px">!} 
After turning off the engine, the antifreeze cools down, the pressure in the cooling system drops. When it drops below a critical level, it opens inlet valve and fed into the system atmospheric air. The pressure in the system equalizes and the inlet valve closes.
Symptoms
The most critical signs of a bad cap are steam from under the hood (if the engine temperature is not in the red sector, 90% chance that the problem is in the cap) and / or swelling of the expansion tank.
You can also make an assumption about the malfunction of the cover, if any:
- coolant leaks from the reservoir;
- antifreeze leaks at joints;
- gusts and swelling of hoses;
- air locks;
- engine overheating.
Data-lazy-type="image" data-src="https://vazremont.com/wp-content/uploads/2018/04/foto-3.jpg" alt="Broken pipe" width="600" height="416" class="lazy lazy-hidden size-full wp-image-5361" srcset="" data-srcset="https://vazremont.com/wp-content/uploads/2018/04/foto-3..jpg 300w" sizes="(max-width: 600px) 100vw, 600px">!} 
Steam, boiling liquid and leaks are associated with wrong work exhaust valve. Air locks are usually caused by a malfunctioning intake or vacuum valve. Bursting (bulging) hoses can be caused by failures of both the exhaust and intake valves.
Air ingress creates air pockets inside the heater core, thermostat, and radiator hoses. As a result, the engine will start to overheat because the cooling system is not able to maintain a constant temperature.
If there are air pockets, you need to completely drain old fluid and fill with new antifreeze. new liquid pour gradually, in small portions of 100 ml.
If there is reason that the cover may be faulty, how to check the cover of the expansion tank VAZ 2114?
In service centers, the check is performed on special stands with a pump and a pressure gauge. The cover is screwed to the rack and the pump starts to supply air. When the pressure gauge reaches 1.5-1.7 atmospheres, it should work Exhaust valve. The operation of the intake valve is checked in the same way, only the air is pumped out from under the cover. If the valves do not work, the plug of the expansion tank VAZ 2114 is faulty.
How can the cap be tested in the field?
Jpg" alt="Check cover" width="600" height="333" class="lazy lazy-hidden size-full wp-image-5362" srcset="" data-srcset="https://vazremont.com/wp-content/uploads/2018/04/foto-4..jpg 300w" sizes="(max-width: 600px) 100vw, 600px">!} 
First you need to carry out visual inspection. Chips, cracks, gaps and other surface damage are grounds for replacement of the part.
Look at the pressure rating listed for the vehicle and compare it to the pressure rating listed on the part. If they do not match, replace the cover.
Visually inspect the condition of the main seal, pressure seal and back seal. Replace part if seals are cracked, hardened, or damaged.
Both exhaust and vacuum safety valve should be easily pulled up and returned back by a spring after they were released. If there is binding, replace the part.
The operation of the exhaust valve is checked by running engine. You need to wait a few minutes after starting the engine until it warms up.
The cooling system will start to work and the pressure in the expansion tank should change. Unscrew the plug of the expansion tank. If you hear a light pop, as when opening a bottle of sparkling water, this is a sign of increased pressure in the cooling system and a working exhaust valve. If there was no cotton, the exhaust valve is defective.
Usually the intake valve is checked on a cold engine. One of the hoses leading from the tank to the radiator is pinched by hand. After the hose is released, it should slowly equalize in thickness. If the hose does not line up, the inlet valve is faulty.
Always check the radiator and expansion tank when replacing a defective cap. It is possible that a malfunction has led to a dangerous build-up of excess pressure and damage or cracks have appeared.
Refinement of the new cover
Unfortunately, the quality of spare parts for domestic cars leaves much to be desired, and it is better to test the new cover on the stand. If the pressure does not hold or the excess pressure does not bleed, you can cut the springs. To do this, the part is disassembled, sealing gum pry off and remove with a screwdriver. Then the inner cover is carefully removed with a screwdriver and the springs are removed.
The large spring is cut one turn and the small spring two turns. As a result, the exhaust valve will begin to open at a pressure of 1 atmosphere, and not 1.7 atmospheres. The inlet valve must be free to blow when checking.
Jpg" alt="Shortening the plug spring" width="670" height="400" class="lazy lazy-hidden size-full wp-image-5363" srcset="" data-srcset="https://vazremont.com/wp-content/uploads/2018/04/foto-5..jpg 300w, https://vazremont.com/wp-content/uploads/2018/04/foto-5-660x394.jpg 660w" sizes="(max-width: 670px) 100vw, 670px">!} 
Preventive measures
To prevent problems, replace the cover every 2-3 years. You also need to control the level of coolant and the pressure in the expansion tank of the VAZ 2114. Constant topping up of antifreeze prevents the occurrence of system overloads. Planned replacement antifreeze within the time recommended by the manufacturer, contributes to the safety of all elements of the cooling system.
Useful video
Additional useful information you can learn from the video below:
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 so that the coolant does not boil while circulating in the system, its boiling point must be much higher, approximately 130 C. Therefore, coolants are initially created with elevated temperature boiling.
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.
The operating pressure in the OSD of 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 Expansion tank bleed valve 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.
The expansion tank cap at first glance may seem like a very simple detail. But in reality, without it, it is impossible to adjust the pressure in the engine cooling system. A defective cap will cause the engine to overheat or damage one of the cooling system components.
The main function of the tank cap
During work power unit pressure builds up in the cooling system. This is caused by the heating of the coolant. High blood pressure requires constant adjustment. That's what the expansion tank cap is for. Maintaining a consistently high pressure helped shift the moment of boiling liquid in the system. At normal atmospheric pressure, water boils at 100°C and antifreeze at about 120°C. normal temperature for most modern engines came close to these marks.
In some situations, the coolant temperature rises rapidly. To prevent the engine from overheating, an increase in pressure is necessary. This is accompanied by an increase in the boiling point of the liquid. In this regard, the experts came to the conclusion that in order to prevent the liquid from boiling in the engine cooling system during its short but significant heating, it is necessary to maintain stable pressure in the system in the range from 1.1 to 1.5 kgf/cm 2 . This is quite enough, since at higher pressure it will be necessary to equip the engines with more reliable and durable cooling system components.
In this regard, the tank lid must maintain pressure to the required value, after which it releases the air inside the tank.
How an expansion tank works
To create the required pressure on the running engine, the cover must ensure tightness. The pressure relief valve is responsible for reducing the pressure. If the pressure in the system exceeds 1.1–1.5 kgf / cm 2, this valve should open. After the pressure drops to operating values, the valve closes.
Also in the cover is an inlet or vacuum valve. It supplies air to the cooling system. After the engine stops, the temperature of the coolant decreases, and the pressure in the system also drops. The volume of liquid in the tank decreases, which entails a pressure drop in the system. This leads to the fact that there is space for air in the expansion tank. At some point, the pressure in the system becomes equal to atmospheric air pressure. If at this point the temperature of the coolant is higher than the temperature of the outside air, its volume will continue to decrease.
As a result of all this, the so-called vacuum or rarefaction effect is created. outside air will put pressure on system components. If one of the parts of the cooling system is leaky, air will be inside it. This results in an air lock. After starting the engine, it can get into the expansion tank. But a variant of the appearance of problems in the normal circulation of fluid in the system is also possible. Sometimes this leads to overheating of the engine or problems in the operation of the heating system.
Air may be in the cooling system due to a violation of the tightness of the pipes and other parts. To avoid this, the pressure in the system must be equal to atmospheric, for which the inlet valve is responsible. It is included in the work if the vacuum reaches 0.03–0.1 kgf / cm 2. This valve supplies the air that was released by the safety valve during the heating of the fluid. Due to this, the pressure in the system does not differ from atmospheric.
Signs of a malfunctioning expansion tank cap
In most cases, the driver pays attention to the cap in case of coolant boiling without serious reasons. In some cases, liquid may be ejected into engine compartment. If at the same time the engine temperature is within the normal range, the reservoir cap is usually the culprit.
Another one possible reason- failure of the intake valve, resulting in air in the system. He formed a plug, the presence of which prevents the proper circulation of the fluid.
The consequences of a malfunctioning expansion tank cap can be extremely unpleasant:
- pipe damage due to natural wear and tear or Low quality details;
- rupture of the thermostat housing;
- leak in the main radiator or stove radiator;
- expansion tank rupture.
Excessively leads to such troubles high pressure in the cooling system of the power unit. The culprit for this is a faulty cover.
How to check the expansion tank cap and prevent negative consequences?
- At the first stage, a routine inspection of the part is carried out for the absence of mechanical damage. If you bought a new cover, it should also be inspected, as cases of factory marriage are not uncommon.
- If appearance cover does not raise any doubts, we check its performance on a running engine. The cap must be screwed on and the engine warmed up to operating temperature then slowly begin to unscrew it. You should hear a hissing sound of air escaping. This is a sign of a properly functioning lid.
- With the engine running, inspect the thick pipes of the cooling system. If the cover does not work, they may be depressed, which is a sign of too much low pressure in system.
- Another option is to unscrew the tank cap and squeeze one of the thick pipes. Next, screw on the lid and release the pipe. If the cover is working correctly, this place should be restored to its original shape.
- The most effective method is to use a pump with a built-in pressure gauge. It is also necessary to prepare an empty expansion tank from any other car. One of its fittings must be connected to the pump hose (without a tip for the nipple) and securely fixed with a clamp. Other tank fittings must be plugged. After that, the tank must be closed with a stopper, the serviceability of which you check.
You can check the expansion tank cap right on your car. It is not necessary to drain the liquid. It is necessary to disconnect the upper pipe from the tank, designed to remove steam from the system. Connect the pump hose to the tank fitting. The opening of the pipe must be plugged. For this, a bolt of the appropriate diameter is suitable. The pressure will increase, so you need to put a clamp on the hose over the bolt and tighten it well so that the bolt does not fly out in the future.
We begin to increase the pressure in the system using a pump. At a certain point, you will hear characteristic sounds - a click and hiss. This is the sound of air being bled from the reservoir cap valve. If the valve worked at a pressure of about 1.1–1.5 kgf / cm 2, and the addition of air only increases the hiss and does not lead to an increase in pressure, the inlet valve is fully functional. Yes, and the safety valve does its job perfectly.
Bought a new cover and it doesn't work?
If checking a new expansion tank cap showed that one or both valves are faulty, you can try to modify the part. Very often, owners of VAZ 2110 and 2114 cars face this problem. Usually, the valves do not work correctly due to the manufacturer using too stiff springs.
First you need to disassemble the cover with a flat screwdriver and pliers. During disassembly, remember exactly how all components were installed, as springs can fly apart into different sides. After disassembly, it is necessary to reduce the length of the springs. The large spring for the pressure relief valve is shortened by one turn, and the smaller by two.
The safety valve spring (large) must be shortened according to when the valve actuated during the cap check. In this case, the main thing is not to overdo it. But with the second spring, everything is much simpler - it must create at least a minimum pressure on the intake valve at the moment it closes. After finalizing the cover, all components must be assembled in reverse order. The plug test must be repeated to ensure that the valves are operating in a timely manner.
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.
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 pockets can be pushed out directly by the coolant 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 inlet or inlet comes to the rescue lid valve, 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 the safety valve of the tank cap holds pressure, it is enough to unscrew the cap with the engine running, 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 constipation on the 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 after new lid to the store.
