What is a car expansion kettle
The car expansion tank (also known as the auxiliary water tank) is an important component of the cooling system, mainly used for storing excess coolant, balancing system pressure, separating gases and preventing cavitation, etc. Youdaoplaceholder0
Core function
Storage of coolant: When the coolant expands and contracts due to temperature changes, the expansion tank can hold the excess liquid to prevent abnormal system pressure.
Pressure regulation: Release excessive pressure through a pressure relief valve to prevent damage to the cooling system.
Gas separation: Collect the gas in the coolant to prevent poor heat dissipation or water hammer (cavitation) caused by gas blockage.
Structure and Usage
It is usually connected to the water tank, engine water channel and water pump, and there are liquid level scale lines inside.
The liquid level check should be carried out when the vehicle is cold to avoid misjudgment at high temperatures.
Precautions
The coolant level should be maintained between the upper and lower limits. Both excessive and insufficient levels may cause problems.
Some models are equipped with liquid level sensors, which will trigger an alarm when the liquid level is low.
The main function of the car expansion kettle (expansion water bottle) is to regulate the pressure of the cooling system, accommodate the excess liquid produced by the thermal expansion and contraction of the coolant, and separate the gas in the system to ensure the engine 's heat dissipation efficiency . The following are the specific functions:
Regulate the system pressure
When the cooling system is in closed operation, the heat generated by the engine's operation will cause the coolant to expand and the internal pressure of the system to rise. The expansion kettle prevents excessive pressure from damaging pipelines or water tanks by absorbing excess liquid and gas.
Accommodate liquids that expand and contract due to temperature changes
When the coolant expands due to heat, some of the liquid flows into the expansion tank. When the temperature drops, the liquid in the expansion kettle is sucked back into the cooling system to maintain a stable liquid level.
Gas separation and cavitation prevention
Gases produced in the cooling system (such as bubbles) can clog the heat dissipation pipes, causing the water temperature to rise or cavitation (when bubbles burst and impact the metal surface). The expansion flask can separate gases and reduce the risk of cavitation.
Pressure relief protection
The lid of the pot is equipped with a pressure relief valve. When the system pressure is too high (such as when the pot boils), it will automatically release the pressure to prevent it from bursting.
Liquid level monitoring
The pot body is marked with scale lines, which is convenient for users to check whether the coolant is sufficient.
Tightening the cap of the car expansion tank too tightly can lead to leakage. The main reason is that excessive tightening will impede the normal operation of the pressure relief valve inside the cap, preventing the normal release of pressure in the cooling system. Eventually, when the pressure is too high, leakage will occur from the weak seal .
The principle of leakage caused by tightening too much
The expansion kettle cap is not an ordinary sealed cap. It is designed with a pressure relief valve (pressure valve) inside, which is used to automatically release the excess pressure in the cooling system when the engine is at high temperature. When the lid is tightened too much:
Youdaoplaceholder0 Pressure relief valve jamming : Over-tightening may deform the spring or gasket of the pressure relief valve, causing the valve to fail to open normally at the preset pressure (typically 1.1-1.4 bar).
Youdaoplaceholder0 Pressure accumulation : When the coolant expands due to heat, the pressure cannot be released through the pressure relief valve and continues to rise until it exceeds the tolerance limit of the kettle or pipeline, forcing the coolant to leak from weak points such as the edge of the kettle lid, the seams of the kettle body, or the pipe joints.
Correct operation and inspection methods
To avoid leakage caused by improper operation, the following steps should be followed:
Youdaoplaceholder0 Moderate tightening force : When installing the lid, simply tighten it by hand until you feel resistance, then rotate it about 1/4 turn. There is no need to over-tighten it with tools.
Youdaoplaceholder0 check the location of the leak :
If the leakage occurs at the edge of the kettle lid and the coolant is turbid with bubbles, it may be due to the failure of the pressure relief valve or the damage of the cylinder gasket, causing high pressure in the system.
If the leakage comes from the seams of the teapot body, it is necessary to check whether the teapot body is aged or cracked.
Youdaoplaceholder0 Test system pressure : When the engine water temperature is normal, press the thickest inlet and outlet water pipes. If the water pipe expands severely and cannot be squeezed, it indicates that the system pressure is too high. It is necessary to check the pressure relief valve or cylinder gasket.
The potential risk of leakage
Long-term neglect of the leakage of the expansion kettle cap may lead to:
Youdaoplaceholder0 engine overheating : After the coolant is lost, the heat dissipation efficiency drops, causing serious faults such as "boiling over" or even cylinder pulling.
Youdaoplaceholder0 kettle burst : Under extreme pressure, the expansion kettle may be damaged, causing coolant to splash and pollute the environment.
Therefore, once leakage is detected, the lid or sealing gasket of the kettle should be replaced in a timely manner, and it is necessary to ensure that accessories that match the vehicle model are selected.
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