What is a thermostat and what is it for?
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What is a thermostat and what is it for?

The thermostat is one of the elements of the engine cooling system. This device allows you to maintain the operating temperature of the motor while it is started.

Consider what function the thermostat performs, its device, as well as possible malfunctions.

What it is?

In short, a thermostat is a valve that responds to changes in the temperature of the medium in which it is located. In the case of a motor cooling system, this device is installed on a fork in two branches of the trunk. One forms the so-called small circle of circulation, and the other a large one.

What is a thermostat and what is it for?

What is a thermostat for?

Everyone knows that during operation the engine is very hot. To prevent it from malfunctioning due to excessively high temperature, it has a cooling jacket, which is connected by means of pipes to the radiator.

As a result of vehicle downtime, all lubricant gradually drains into the oil pan. It turns out that in a cold motor there is practically no lubrication. Given this factor, when an internal combustion engine is started, it cannot be given heavy loads so that its parts do not wear out faster than usual.

Cold oil in the sump is more viscous than when operating the power unit, so it is more difficult for the pump to pump it to all nodes. To speed up the process, the engine must reach operating temperature as soon as possible. Then the oil will become more fluid and the parts will be lubricated faster.

The first car developers had a difficult task: what should be done so that the engine warms up quickly, but its temperature was stable during operation? For this, the cooling system was modernized, and two circulation circuits appeared in it. One provides fast heating of all parts of the engine (antifreeze or antifreeze is heated from the hot walls of the cylinders and transfers heat to the entire engine body). The second is used to cool the unit when it reaches operating temperature.

What is a thermostat and what is it for?

The thermostat in this system plays the role of a valve, which deactivates the heating of the motor at the right time, and connects the radiator to maintain the internal temperature of the engine. What makes this result possible?

Where is the thermostat in the car?

In most models, the auto thermostat looks almost the same, with the exception of some design features. The thermostat will be located at the junction of the pipes coming from the engine and from the cooling radiator. These elements will be connected to the thermostat housing. If this mechanism does not have a housing, then it will be installed in the engine jacket (cylinder block housing).

Regardless of the location of the thermostat, at least one branch pipe of the cooling system going to the radiator will necessarily depart from it.

The device and principle of operation of the thermostat

The thermostat design includes:

  • Cylinder Basically, its body is made of copper. This metal has good thermal conductivity.
  • Inside it is a filler. Depending on the model of the part, it can be made of water and alcohol, or it can be made of wax mixed with powder of copper, aluminum and graphite. This material has a large coefficient of thermal expansion. While the wax is cold, it is hard. As it expands, it expands.
  • The stem is made of metal. It is placed inside the cylinder.
  • Rubber compressor. This element prevents the filler from entering the coolant and moves the stem.
  • Valve. There are two of these elements in the device - one at the top of the thermostat and the other at the bottom (in some models it is one). They open / close the small and large contours.
  • Body. Both valves and cylinder are fixed on it.
  • Springs provide the necessary resistance to the movement of the rod.
What is a thermostat and what is it for?

The whole structure is placed inside the branch between the small and the big circle. On the one hand, an inlet pipe of a small circuit is connected to the assembly, and on the other, an input of a large one. There is only one way out of the branch.

While the coolant circulates in a small circle, it gradually heats the thermostat cylinder. Gradually, the temperature of the medium rises. When the indicator reaches from 75 to 95 degrees, the wax has already melted (metal granules accelerate the process) and begins to expand. Since he does not have enough space in the cavity, he presses on the rubber stem seal.

When the power unit has warmed up sufficiently, the valve of the large circle begins to open, and antifreeze (or antifreeze) begins to move in a large circle through the radiator. Since the operation of the stem directly depends on the temperature of the liquid in the channel, the device allows you to maintain the optimum temperature of the motor at any time of the year: in the summer it does not allow it to overheat, and in winter it quickly reaches the operating temperature.

Regardless of the thermostat modifications, they all work on the same principle. The only difference between them is the temperature range at which the valve is triggered. This parameter depends on the brand of the engine (each of them has its own operating temperature, so the valve should open in a predetermined range).

Depending on the region in which the car is operated, a thermostat should also be selected. If the main part of the year is hot enough, then you should put a thermostat, which works at a lower temperature. In colder latitudes - on the contrary, so that the motor warms up sufficiently.

What is a thermostat and what is it for?

To prevent the motorist from installing the wrong part, the manufacturer indicates the valve opening parameter on the device’s body.

In addition, all thermostats are different from each other:

  • The number of valves. The simplest design is with one valve. Such modifications are used in older cars. Most modern cars use a two-valve option. In such modifications, the valves are fixed on one stem, which ensures their synchronous movement.
  • One and two steps. Classic cooling systems use single-stage models. If the fluid flows under pressure in the circuit, then two-stage thermostats are installed. In such models, the valve consists of two elements. One of them works with less effort to relieve pressure, and after that the second is activated.
  • With and without housing. Most models are open. To replace it, you need to disassemble the node in which it is installed. To facilitate the task, manufacturers implement some modifications already assembled in a special block. It is enough to connect the corresponding nozzles.What is a thermostat and what is it for?
  • Heated. On some vehicles, thermostats with a temperature sensor and a cylinder heating system are installed. Such devices are controlled by the computer. The main task of such devices is to change the temperature range of valve opening. If the motor works without heavy loads, then the thermostat works as usual. If the unit is under additional load, electronic heating forces the valve to open earlier (the coolant temperature is approximately 10 degrees lower). This modification allows you to save a little fuel.
  • The dimensions. Each cooling system uses pipes not only of different lengths, but also of diameter. In connection with this parameter, the thermostat must be selected, otherwise the antifreeze will freely flow from a small circuit to a large one and vice versa. If a case modification is purchased, then the diameter of the nozzles and their angle of inclination will be indicated in it.
  • Complete set. This setting is vendor specific. Some sellers sell devices with high-quality gaskets, while others put a lower-quality consumable in the kit, but offer to buy a more durable analogue.

Types and types of thermostats

Among all types of thermostats, there are:

  1. Single valve;
  2. Two-stage;
  3. Two-valve;
  4. Electronic.

The key difference between these modifications is in the principle of opening and in the number of valves. The simplest type of thermostat is a single valve. Many models of foreign production are equipped with such a mechanism. The operation of the thermostat boils down to the fact that when a specific temperature is reached, the valve opens a large circulation circuit without closing the small circuit.

Two-stage thermostats are used in systems where the coolant is under high pressure. Structurally, this is the same single-valve model. Its plate consists of two elements of different diameters. First, a small plate is triggered (due to its small diameter, it moves more easily in a circuit with high pressure), and behind it the circle is overlapped by a large plate. So in these systems, the motor cooling circle is turned on.

The two-valve modification of thermostats is used in the device of cooling systems of domestic cars. Two valves are installed on one actuator. One is responsible for the outline of the large circle, and the other for the small one. Depending on the position of the actuator, one of the circulation circles is closed.

What is a thermostat and what is it for?

In electronic thermostats, in addition to the main element that heats up from the coolant temperature, an additional heater is also installed. It connects to the control unit. Such a thermostat is controlled by an ECU, which determines the operating mode of the motor and adjusts the cooling system to this mode.

Checking the thermostat in the car

There are two ways to check the health of a device:

  • By dismantling from the system;
  • Without removing from the car.

The first method is rarely used. Some resort to it to fully verify its performance. Also, this method will allow you to check the performance of the new part, since this cannot be done in the store. To do this, you need to heat the water (boiling water - above 90 degrees). The part is dipped into a container with boiling water.

If after a couple of minutes the valve does not open, then the part is faulty - either something happened to the stem, or to the spring, or maybe something happened to the container in which the wax is located. in this case, the thermostat must be replaced with a new one.

For more details on how to check a new part, see the video:

Checking the car thermostat

How to determine if it works or not?

You don't need to be a leading mechanical expert to test the thermostat on the machine without removing it. It is enough to understand how the device works. During the first minutes of engine operation, the entire cooling system should not heat up. With this in mind, you need to do the following:

  1. Start the engine and let it run.
  2. At this point, you should try the pipes connected to the radiator. If the thermostat is working, the system will not heat up for up to five minutes (depending on the ambient temperature). A cold system indicates that the valve is closed.
  3. Next, look at the dashboard arrow. If it rises quickly and goes far beyond the 90 degree mark, we try the pipes again. A cold system indicates that the valve is not operating.What is a thermostat and what is it for?
  4. Ideally, the following should happen: while the engine warms up, the cooling system is cold. As soon as it reaches the desired temperature, the valve opens and the antifreeze goes along a large circuit. In this case, the bypass is gradually cooled.

If there are irregularities in the operation of the thermostat, it is best to replace it immediately.

Hot and cold thermostat. Opening temperature

When replacing a thermostat, it is recommended to buy a factory analogue. It opens at a coolant temperature of 82 to 88 degrees. But in some cases, a custom thermostat will come in handy.

For example, there are “cold” and “hot” thermostats. The first type of devices open at a temperature of about 76-78 degrees. The second is triggered when the coolant warms up to almost 95 degrees.

A cold thermostat can be installed instead of a standard one in a car, the engine of which warms up very quickly and often reaches the boiling point. Of course, such a modification of the cooling system will not eliminate a similar engine problem, but a poorly warmed up engine will boil a little later.

if the car is operated in northern latitudes, then motorists modify the cooling system towards a higher opening temperature of the thermostat. With the installation of the "hot" option, the engine cooling system will not overcool the internal combustion engine, which will have a positive effect on the operation of the stove.

What are the faults?

Since the thermostat must always respond to temperature changes in the engine cooling system, it must be functional. Consider the main malfunctions of the thermostat in the cooling system. In fact, there are two of them: locked in the closed or open position.

Stuck in fully closed position

If the thermostat stops opening, then while the engine is running, the coolant will circulate only in a small circle. This means that the engine will heat up properly.

What is a thermostat and what is it for?

But due to the fact that the internal combustion engine that has reached the operating temperature does not receive the necessary cooling (antifreeze does not circulate in a large circle, which means that it does not cool in the radiator), it will very quickly reach the critical temperature indicator. Moreover, the internal combustion engine can boil even when it's freezing outside. To eliminate such a malfunction, it is necessary to replace the thermostat with a new one.

 "Hangs" in fully or partially open state

In this case, the coolant in the system from the start of the engine immediately begins to circulate in a large circle. It will take much more time for the internal combustion engine to reach operating temperature (thanks to this, the engine oil will properly warm up and lubricate all parts of the unit with high quality).

If the thermostat fails in winter, then the engine will warm up even worse in the cold. If in summer this is not a particular problem, then in winter it will be impossible to heat up in such a car (the radiator of the stove will be cold).

Is it possible to drive without a thermostat

A similar thought comes to car owners, who in the summer are constantly faced with overheating of the car. They simply remove the thermostat from the system, and the antifreeze immediately goes in a large circle when the internal combustion engine is started. Although this does not immediately disable the motor, it is not recommended to do so (the engineers knowingly invented and installed this element in the car).

What is a thermostat and what is it for?

The reason is that a thermostat in the car is needed to stabilize the temperature of the motor. It does more than just warm up or cool the powertrain. If you remove this element from the cooling system, then the car owner forcibly turns off the internal combustion engine heating circuit. But an open thermostat does not only turn on a large circle of circulation.

At the same time, it blocks the small circulation circle. If you remove the thermostat, then, depending on the type of cooling system, the pump will press the antifreeze immediately in a small circle, even if the thermostat is removed from the system. The reason is that circulation will always follow the path of least resistance. Therefore, wanting to eliminate overheating of the motor, the motorist can arrange local overheating in the system.

But a poorly heated engine can suffer no less than overheating. In a cold engine (and when circulating in a large circle at once, its temperature may not even reach 70 degrees), the air-fuel mixture burns poorly, which will cause carbon deposits in it, spark plugs or glow plugs will fail faster, and lambda will suffer. probe and catalyst.

It is much better, with frequent overheating of the motor, not to remove the thermostat, but to install a cold analogue (it opens earlier). You should also find out why the engine overheats so often. The reason could be a clogged radiator or a poorly functioning fan.

Video - checking work

A broken thermostat is critical to the engine. In addition, read a detailed overview of how the thermostat works as well as the test options:

Questions and answers:

What is a thermostat and what is it for? This is a device that reacts to changes in the temperature of the coolant, and changes the mode of circulation of antifreeze / antifreeze in the cooling system.

What is the thermostat used for? When the motor is cold, it needs to warm up quickly. The thermostat blocks the circulation of coolant in a large circle to maintain the operating temperature of the internal combustion engine (in winter it prevents the engine from freezing).

What is the life of the thermostat? The service life of the thermostat is about two to three years. It depends on the quality of the part itself. If it is not replaced, the motor will overheat or, on the contrary, it will take a very long time to reach the operating temperature.

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