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Cover of a broad tank: why it is necessary also what will be at its malfunction?

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Long evolution of internal combustion engine could not change the main thing: it and remained the thermal car, and therefore a lot of things depend on serviceability of its cooling system. Touching upon subject of the main reasons for escapes of antifreeze, we remembered among probable options and cap of expansion chamber. Sometimes this small detail spoils life to many motorists and their cars much more, than it is possible to imagine. Today we will understand in detail what role it plays in the cooling system and that can occur at its misoperation and also how to buy qualitative cap of expansion chamber and even to repair it.

Why the cap of expansion chamber is necessary?
The expansion chamber carries out role of compensatory: heating up, the cooling fluid considerably extends in volume. In very old cars the separate expansion chamber was not, and its role was played by radiator.

The radiator stopper at the same time carried out the same task, as by modern cars: thanks to existence in a design of the steam discharge (final) valve it supported let and the small, but excessive pressure (0.45-0.55 kgfs/cm2) in a system that allowed water to begin to boil only at 109-112 degrees.

Also the air valve adjusted on depression (0.01-0.10 kgfs/cm2) was provided in a cover of a radiator. Its task was opposite – not to allow creations of too low pressure in a system

The modern cover of a broad tank though looks differently, than the “vintage” stopper of a radiator, but is arranged probably. As a rule, in the plastic case two valves – final and inlet are provided.

Problem of the first – “to pit” pressure if it reached the limit provided by the producer. As modern motors have more high working temperatures, than at engines of former generations, final valves of a cover of a tank at them can open with a pressure up to 1.5 kgfs/cm2, and this parameter is strictly regulated for each concrete motor.

The inlet valve opens at 0.03-0.13 kgfs/cm2 that allows to avoid excessive depression in a system. Some producers structurally unite two valves in one, but their essence from it does not change.

Why it is necessary to control yes sir pressure in the cooling system?
Maintenance of the necessary pressure in a system is important for two reasons. First, it should not be too low that antifreeze could begin to boil at more high temperature, than it occurs with an atmospheric pressure. Many modern motors in operating time can heat up to 120 degrees and more while the majority of cooling liquids under normal conditions begins to boil already at 110 degrees. Elevated pressure allows to avoid overheating and boiling of antifreeze even at high temperatures.

And secondly, pressure in the cooling system should not be too high to avoid leak of antifreeze and ruptures of rubber branch pipes and a plastic broad tank – that is, to keep the system of tight. By the way, maintaining tightness is quite often prevented by not only low-quality operation of valves of a cover of a tank, but also the landing surfaces of a jellied mouth or a carving on the cover: if they are badly processed – wait for leaks.

It is possible to see similar quality of processing the of the planes on the tanks which are on sale in shops for Lada seldom presently – and therefore the ideal tightness of connections should not wait

What covers happen?
Let’s consider several different covers of a broad tank on the example of front-wheel Lada. For it on sale it is possible to meet nearly ten covers of the most different producers. They can differ considerably in color of the case, inscriptions, a carving and “stuffing”, but the essence from it does not change: the final valve has to work at 1.1 atmospheres (so usually in common people call pressure parameter a kilogram force on square centimeter).

Unfortunately, the covers which are found on sale are good and bad, that is qualitative and not really. And it means that they can allow excessive pressure in a system much above normal – 1.3-1.5 kgfs/cm2 and even above!

Some covers can dump pressure to demanded, but do it too long and reluctantly. And still the cover can not hold and half from the necessary excessive pressure, opening the final valve already at 0.5-0.6 atmospheres.

Both, and the third is almost equally bad. In the first two cases excessive pressure in a system will keep at higher level, in the third – not to reach the required parameter. That is, in the first two cases the driver can learn about malfunction of a cover only after a rupture of a branch pipe or a broad tank, and in the second the car can “boil”, exhausting through a tank cover even if on the street not hot.

What will be at failure of valves in cap?
The most frequent option – the wedged or incorrectly working outlet valve. In this case in system the excessive excessive pressure which victim many elements – expansion chamber, branch pipes, radiators can fall is created … If you saw the cars standing in hot day on the road with open cowl and pool under them, the cap with faulty outlet valve could be the cause of emergence of this pool.

One of visual signs of failure of outlet valve – excessively inflated tank. Unfortunately, it can be defined not on all cars as at many cars tanks are made of opaque and not too elastic material. Also high pressure leads to antifreeze after dribble in joints even if they are rather strongly tightened.

Malfunction of the inlet valve is expressed that branch pipes, especially large, and sometimes and a tank visually contract. Excessive depression in a system also does not add durability to its details.

How to choose and check a cover of a broad tank?
It is visually impossible to define correctness of settings of valves in a cover. Also the simple, but special stand with the manometer on which the cover is wound is for this purpose necessary let. Then in installation the excessive pressure, and then depression is created at first. The received figures compare to factory parameters in the table.
In reality there are no test devices in shops usually, and the role of the test stand carries out already engine. That is, when choosing a cover in shop it is possible to be guided only by indirect indicators – the price, the producer and visual quality of production. And after replacement of a cover it is necessary to observe whether she creates excessive pressure in a system. Some of signs of it can consider maintenance of normal operating temperature without signs of boiling of cooling liquid: if the engine long works, and from under a cover there are no couples, then everything is all right. Some car owners check pressure in a system, slightly priotkruchivy a cover at the heated-up engine: in this case hissing which speaks about pressure release which is supported by a serviceable cover has to sound. Such check is effective, but is unsafe: if suddenly breaks a cover, the boiling cooling liquid can strike with the fountain from a tank and burn hands and a face.

One more essential occasion to think of serviceability of a cover – loss of tightness of a system or a serial output out of operation its details: tank, radiators, heater crane and so on. At last, excessively heated engine at a clean radiator and the serviceable thermostat is also a reason for survey of a cover

And “approximately” to be convinced of serviceability of the inlet valve, it is possible to turn off a cover and to squeeze one of thick branch pipes then again to twirl it. If the branch pipe takes the former form, then in a system excessive depression is not created.

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