Car thermostat.
Product action
The thermostat must be kept in good working condition, otherwise it will seriously affect the normal operation of the engine. If the thermostat opens (here are the main valve of the knuckle thermostat) too late or even can not open, it will cause the engine to overheat; Open too early, the engine preheating time is extended, so that the engine temperature is too low.
Working principle
Thermostat (Thermostat) is a kind of automatic temperature control device, usually contains temperature sensing components, by expansion or contraction to open, turn off the flow of coolant, that is, according to the temperature of the cooling liquid automatically adjust the water into the radiator, change the coolant circulation range, to adjust the cooling system's cooling capacity.
The thermostat used by the engine is mainly a wax thermostat, which is controlled by the paraffin wax inside the coolant circulation through the principle of thermal expansion and cold contraction. When the cooling temperature is lower than the specified value, the refined paraffin in the temperature sensing body of the thermostat is solid, the thermostat valve closes the channel between the engine and the radiator under the action of the spring, and the coolant returns to the engine through the water pump for small circulation in the engine. When the coolant temperature reaches the specified value, the paraffin begins to melt and gradually become a liquid, the volume increases and presses the rubber tube to shrink, while the rubber tube shrinks, the push rod acts on the upward thrust, and the push rod has the 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 pump for large circulation. Most of the thermostat is arranged in the cylinder head outlet pipe, which has the advantage of simple structure and easy discharge of bubbles in the cooling system; The disadvantage is that the thermostat often opens and closes when working, resulting in oscillation.
When the engine operating temperature is low (below 70°C), the thermostat automatically closes the path to the radiator, and opens the path to the pump, the cooling water flowing from the jacket directly through the hose into the pump, and the pump into the jacket for circulation, because the cooling water does not dissipate by the radiator, can make the engine operating temperature rise rapidly, this cycle route is called small cycle. When the engine operating temperature is high (80°C or more), the thermostat automatically closes the path leading to the pump, and opens the path leading to the radiator, the cooling water flowing from the jacket is cooled by the radiator and then sent to the jacket by the pump, improving the cooling intensity to prevent the engine from overheating, this cycle route is called the large cycle. When the engine operating temperature is between 70 and 80°C, large and small cycles exist at the same time, that is, part of the cooling water for large circulation, while the other part of the cooling water for small circulation.
The role of the car thermostat is to shut down before the temperature of the car has not reached the normal temperature, and the coolant of the engine is returned to the engine by the water pump to carry out small circulation in the engine, so that the engine can heat up rapidly. When the normal temperature is exceeded, it can be opened to allow the coolant to circulate through the radiator circuit of the entire tank for rapid heat dissipation.
Product inspection
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 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, the thermostat of the Santana JV engine, the opening temperature of the main valve is 87 ° C plus or minus 2 ° C, the full opening temperature is 102 ° C plus or minus 3 ° C, and the full opening lift is > 7mm.
Fault phenomenon
Under normal circumstances, when the engine starts, the working temperature is very low, in order 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.
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