What is the function of the Thermostat?

The thermostat is one of the main components of the cooling system of automobiles and tractors,it is also called Water Bladder. Its main function is to ensure that the engine can be quickly and evenly preheated by controlling the large and small circulation of the engine coolant, thereby greatly reducing the need for starting to normal operating temperature.Time, and will not be too cold or too hot when the vehicle is driving. The thermostat automatically adjusts the amount of water entering the radiator according to the temperature of the cooling water and changes the water circulation range to adjust the heat dissipation capacity of the cooling system to ensure that the engine works within a suitable temperature range. The thermostat must be kept in good technical condition, otherwise it will seriously affect the normal operation of the engine. If the main valve of the thermostat is opened too late, it will cause the engine to overheat; if the main valve is opened too early, the engine warm-up time will be prolonged and the engine temperature will be too low. For example, after the engine is working normally, the temperature of the engine may be too low if there is no thermostat when it is driven in winter. At this time, the engine needs to temporarily stop water non-circulation to ensure that the engine temperature is not too low.

Where is the thermostat installed？

Generally, the coolant of the water cooling system flows in from the body and flows out from the cylinder head. Most thermostats are arranged in the water outlet pipe of the cylinder head. The advantage of this arrangement is that the structure is simple and the bubbles in the water cooling system are easily eliminated; the disadvantage is that the oscillation phenomenon will occur when the thermostat is working. For example, when starting a cold engine in winter, the thermostat valve is closed due to the low coolant temperature. When the coolant is in a small cycle, the temperature rises quickly and the thermostat valve opens. At the same time, the low-temperature coolant in the radiator flows into the body, so that the coolant cools down again, and the thermostat valve closes again. When the coolant temperature rises again, the thermostat valve opens again. Until the temperature of all the coolant is stable, the thermostat valve becomes stable and no longer opens and closes repeatedly. The phenomenon that the thermostat valve repeatedly opens and closes in a short period of time is called thermostat oscillation. When this phenomenon occurs, it will increase the fuel consumption of the car. The thermostat can also be arranged in the water outlet pipeline of the radiator. This arrangement can reduce or eliminate the phenomenon of thermostat oscillation, and can accurately control the temperature of the coolant, but its structure is complicated and the cost is high, and it is mostly used in high-performance cars and cars that often drive at high speeds in winter.

The working principle of Thermostat

The main thermostat used is a wax type thermostat. When the cooling temperature is lower than the specified value, the fine paraffin in the thermostat body is solid, and the thermostat valve closes the engine and the radiator under the action of the spring. The cooling fluid is returned to the engine through the water pump to carry out a small circulation in the engine. When the coolant temperature reaches the specified value, the paraffin wax begins to melt and gradually becomes liquid, and the volume increases and compresses the rubber tube to shrink it. When the rubber tube is contracted, an upward thrust is applied to the push rod, and the push rod has a downward reverse thrust on the valve to open the valve. At this time, the coolant flows through the radiator and the thermostat valve, and then flows back to the engine through the water pump for a large cycle.

Most of the thermostats are arranged in the water outlet pipeline of the cylinder head. The advantage of this is that the structure is simple and it is easy to eliminate air bubbles in the cooling system; the disadvantage is that the thermostat is often opened and closed during operation, causing oscillation.

State judgment of Thermostat

When the engine starts to run cold, if there is still cooling water flowing out of the water inlet pipe of the water tank, it means that the main valve of the thermostat cannot be closed; when the engine cooling water temperature exceeds 70℃, the water tank of the water tank enters If there is no cooling water flowing out of the water pipe, it means that the main valve of the thermostat cannot be opened normally, and repair is required at this time. The thermostat inspection can be carried out on the car, the method is as follows: Inspection after engine start: Open the radiator water filler cap. If the cooling level in the radiator is static, it means that the thermostat is working normally, otherwise, it means that the thermostat is working abnormally. This is because when the water temperature is lower than 70°C, the thermostat expansion cylinder is in a contracted state and the main valve is closed; when the water temperature is higher than 80°C, the expansion cylinder expands, the main valve gradually opens, and the circulating water in the radiator begins to flow. When the water temperature gauge indicates below 70℃, if there is water flowing at the water inlet pipe of the radiator and the water temperature is warm, it means that the main valve of the thermostat is not closed tightly and the cooling water is circulated prematurely. Check after the water temperature rises: the water temperature rises quickly at the beginning of the engine operation; when the water temperature gauge indicates 80, the heating rate slows down, which indicates that the thermostat is working normally. On the contrary, if the water temperature has been rising rapidly, when the internal pressure reaches a certain level, the boiling water suddenly overflows, which indicates that the main valve is stuck and suddenly opened. When the water temperature gauge indicates 70℃-80℃, open the radiator cover and the radiator water release switch, and feel the water temperature with your hands. If they are hot, the thermostat is working normally; if the water temperature at the water inlet of the radiator is low and the radiator is filled with water There is no water or very little water flowing out of the water inlet pipe of the chamber, indicating that the main valve of the thermostat cannot be opened.

Note:

Thermostats that are stuck or not closed tightly should be removed for cleaning or repair, and should not be used.