The function of the car thermostat
The main function of the car thermostat is to automatically adjust the circulation path of the coolant based on the engine temperature, ensuring that the engine operates within the optimal temperature range.
Quick heating: When the engine is cold-started, the thermostat closes the path to the radiator, and the coolant only circulates within the engine (a small circulation), helping the engine quickly reach the normal operating temperature.
Preventing overheating: When the engine temperature rises, the thermostat opens, and the coolant flows through the radiator for a large circulation, dissipating heat in time to prevent the engine from overheating.
Optimizing performance: By maintaining an appropriate temperature, the thermostat helps improve fuel economy, reduce wear, and extend the engine lifespan.
A damaged car thermostat can cause the engine temperature to be out of control. Specifically, it manifests as the engine overheating or failing to reach the normal operating temperature, thereby triggering a series of performance and durability issues.
Core impact and specific manifestations
Thermostat damage can be divided into two states: stuck in the fully open position or stuck in the fully closed position. The effects on the vehicle are completely different.
Thermostat fully open (engine unable to heat up)
Fuel consumption significantly increases: When the engine operates at a low temperature for a long time, the fuel is not atomized properly, and the computer will increase the fuel injection volume to maintain operation. The fuel consumption may increase by 10%-15%.
Heating and warming system failure or extremely poor performance: As the heat is continuously dissipated in the large circulation of the coolant, the air outlet temperature of the heating system is low, seriously affecting the comfort of driving and riding in winter.
Increased engine wear and reduced power: At low temperatures, the engine oil has high viscosity, and the lubrication effect is reduced. The friction resistance of internal parts increases, accelerating wear and resulting in insufficient power output. At the same time, low combustion efficiency also directly weakens power.
Thermostat fully closed (engine overheating)
High risk of engine damage: The coolant cannot enter the large circulation for heat dissipation, and the heat accumulates, easily causing the engine to "boil" (the coolant boiling), which may result in cylinder liner damage, piston pulling, and even engine.
Power loss and emission： Overheating may cause components such as valves to become stuck， resulting in abnormal operation； at the same time， high temperature may cause the emission control devices such as the three-way catalytic converter to fail， leading to excessive exhaust emissions.
Related system chain damage： Persistent high temperature also damages the fuel system， lubrication system， etc.， significantly increasing the subsequent maintenance costs and complexity.
Identification methods for faults
In addition to observing abnormal readings on the water temperature gauge (long-term low temperature or rapid rise to the red line)， the following methods can be used to preliminarily determine：
Touch the temperature difference of the radiator water pipes： After the engine starts for 3-5 minutes， touch the upper and lower water pipes of the radiator. Under normal circumstances， the upper pipe is hotter first， and the lower pipe is hotter later. If the temperatures of both pipes are always the same or the temperature difference is extremely large (more than 15°C)， the thermostat may be faulty.
Pay attention to the changes in heating and fuel consumption： If the heating system does not heat for a long time in winter， or the fuel consumption suddenly increases by 5%-10% recently， accompanied by unstable idle， it can be used as an auxiliary clue for judgment.
Listen for abnormal sounds： There may be a "gurgling" sound or metal friction sound during the coolant circulation.
Recommendations for repair and maintenance
The impact of thermostat failure has progressive and interrelated effects， ranging from performance decline to core component damage. Therefore：
Timely inspection and replacement： Once the above signs are observed， it is necessary to check immediately. The replacement cost of the thermostat itself is usually not high， but delaying the repair may lead to major engine repairs， resulting in huge costs.
Perform preventive inspections： It is recommended to conduct special inspections of the cooling system and thermostat when the vehicle has traveled 8-100，000 kilometers to prevent problems before they occur. Do not attempt to remove it yourself: Removing the thermostat will cause the engine temperature to completely lose control. Cold starts will be extremely slow to heat up, and at high temperatures, it is prone to overheating, which will significantly increase fuel consumption, power loss and engine wear, and severely shorten the engine's lifespan.
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