What is the purpose of a thermostat in an engine?


The thermostat is a valve that controls the flow path of the engine coolant. The part automatically adjusts the amount of water entering the radiator according to the temperature of the cooling water to ensure that the engine works in a suitable temperature range and can save energy consumption. Because the engine is very fuel-intensive at low temperatures, the damage to the car is larger, including easily producing carbon deposits and bringing a series of problems. Therefore, the thermostat must be kept in good working condition, otherwise, it will seriously affect the normal operation of the engine.


Working principle of thermostat

To understand the working principle of the thermostat, we must first understand the structure of the thermostat.

There are two kinds of temperature savers: spring box type and wax type. We widely use wax type temperature saver, which is installed at the water outlet of the cylinder head. Wax thermal sensitive material has the characteristics of accurate temperature control, stable work, heat, pressure, frost resistance, long service life and so on. It is mainly composed of a main valve, auxiliary valve, support, spring, and induction body.


The induction body is a rigid sealed space composed of the induction body shell and cover. The upper end of the guide rod is connected to the main valve, and the lower end is covered with a rubber tube. The annular space formed by the rubber tube and the induction shell is filled with low-melting ash and paraffin wax or a mixture of aluminum powder and paraffin wax. One end of the spring is supported on the housing, and the other end is pressed on the spring seat on the main valve, and the main and auxiliary valves are linked with the guide rod.


The operation of the thermostat

When the outlet temperature is lower than 80℃, the main valve is closed and the auxiliary valve is fully opened. Cooling water does not go through the radiator, directly back to the pump for small circulation. When the outlet temperature is higher than 84℃, the paraffin mixture begins to melt, and the volume expansion extrusion hose produces an axial component force on the guide rod cone, forcing the guide rod compression spring to move upward, and the main valve opened and the small auxiliary valve is closed.


As the water temperature continues to rise, the main valve gradually opens, and the auxiliary valve gradually closes. There are big cycles and small cycles. When the outlet temperature reaches 95℃, the main valve is fully opened, the auxiliary valve is fully closed, and the cooling water is circulated. For accurate measurement, the thermostat can be removed and placed in water, and gradually heated, with a thermometer to measure the water temperature observe the opening and closing of the main and secondary valves of the thermostat, and measure the lift. If not reached the technical indicators should be replaced.


The fault of the thermostat

Under normal circumstances, when the engine starts, the working temperature is very low, to make the temperature rise faster, then through the thermostat control (thermostat main valve closed), so that the coolant by the liquid pump into the water pipe, the coolant does not flow through the radiator, this is a small cycle when the temperature of the coolant reaches 87 degrees (Bora thermostat open temperature of 87 degrees, After that, the thermostat valve opens, the coolant begins to flow through the radiator, and the cooling system enters a large cycle. Generally speaking, about five minutes after the car starts, the coolant temperature can reach the normal temperature of 85~105 degrees, if the normal working temperature has not been reached for a long time, or the temperature has risen more than 110 degrees, it should be suspected whether the thermostat is faulty.



When do I need to replace the thermostat?

The safe life of the wax thermostat is generally 50,00km, so it is required to replace it regularly according to its safe life. Check the method of thermostat in the temperature adjustable thermostat heating equipment check the opening temperature of the thermostat main valve, full open temperature, and lift, one of which does not meet the standard set value, the thermostat should be replaced.

For example, in the thermostat of the Santana JV engine, the opening temperature of the main valve is 87 ℃plus or minus 2℃, the full opening temperature is 102℃ plus or minus 3℃, and the full opening lift is > 7mm.



The secret of the thermostat is the small cylinder located on the engine side of the device. The cylinder is filled with wax and begins to melt at about 180 degrees Fahrenheit. Different thermostats turn on at different temperatures, but 180 F /82℃ is a common temperature. The rod attached to the valve is pressed into the wax. When the wax melts, it expands significantly and pushes the rod out of the cylinder, opening the valve. If you need a thermostat, you can contact us, we will provide you with high-quality products.



What are the signs that a thermostat is malfunctioning?

Signs include very high-temperature readings, engine overheating, coolant leaks, and temperature instability.


What happens if I drive my car without a thermostat?

A car without a thermostat will not allow the engine to operate at optimum temperature. It can also cause the heater to emit cold air.

Relating reading:

How to judge engine Cylinder Head Gasket ablation failure? What are the precautions for replacing the Cylinder Head Gasket?


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