The quality of the engine's cooling system will affect the overall reliability of the vehicle and the length of the engine's life. Through the operation of various parts of the cooling system, the heat generated by combustion or friction inside the engine and gearbox will be taken away and released into the atmosphere.
What is an Engine Cooling System?
The engine is a complex component. When the engine is started, it is necessary to heat the engine very quickly, but when it is driven under a high load, the engine must be kept cool. When the engine is too cold, it is easy to cause wear and tear inside the engine during operation, and it will also become more energy-intensive, and water and sludge will easily accumulate in the crankcase. When the engine overheats, it will cause the engine to produce pre-ignition, knocking, and other damage to the engine. So, the cooling system of the car is important for the engine.
Although the engine has been improved for many years, the efficiency of the engine is still not high in the process of converting chemical energy into mechanical kinetic energy. About 70% of the gasoline will be converted into heat, and the heat is dissipated by the vehicle cooling system. task. If the engine heats up, it wears out components faster, making the engine less efficient and emitting more waste and pollutants. Therefore, the important role of the cooling system is to heat the engine as soon as possible and keep it at a constant temperature. Most of the heat generated during the combustion process is expelled from the exhaust pipe, but some of the heat remains trapped in the engine, causing it to heat up. The engine runs optimally when the coolant temperature is about 93°C.
The quality of the engine's cooling system will affect the overall reliability of the vehicle and the length of the engine's life. Through the operation of various parts of the cooling system, the heat generated by combustion or friction inside the engine and gearbox will be taken away and released into the atmosphere. The pressure generated by the pump will drive the cooling water to circulate in the water channel inside the engine, and the cooling water will absorb the waste heat of the engine during the flow, and then flow to the radiator to dissipate the heat into the atmosphere through heat exchange. The cooling system also includes a thermostat, whose openings can be changed in size to regulate the flow of cooling water, keeping the water temperature stable and making the engine run more efficiently.
The main factor affecting the replacement of cooling system parts is the frequency of regular maintenance. Most vehicles should have their cooling water replaced once a year. The flushing of the cooling system and the replacement of the cooling water are the basic work of the cooling system maintenance because the new antifreeze absorbs heat better, which can make the engine temperature easier to maintain at a lower range. At the same time, thorough flushing can remove the deposits in the cooling system and avoid damage to related parts due to the accumulation of deposits over time.
In addition, the cooling water level should also be checked regularly. The inspection method is simple, just observe the scale on the plastic water tank next to the water tank. If there is no water in the water storage tank, when you need to open the water tank cover to check, it must be done after the car is cold or the engine is cooled down. Otherwise, you may be scalded by the hot water and steam in the water tank. If the cooling water is insufficient and needs to be added, you can mix half of the antifreeze and distilled water. The driver can visually check whether the appearance of the water pipes, belts, and water tanks is abnormal, the water tank is leaking, the water pipes are swollen and deformed, the belts are cracked or there are burrs due to wear, etc., which are all signs that the cooling system needs maintenance.
Function and Method Category of the Cooling System:
Keep the engine at normal operating temperature without overcooling or overheating the engine, resulting in wasted fuel or damage to engine parts.
- Air-cooled: Use a cooling fan to force air to cool the engine, but its cooling effect is poor.
- Water-cooled type: It uses water as the cooling medium, and the cooling effect is good. Generally, it is used in automobile engines.
Engine cooling principle:
- The pistons are primarily cooled by oil sprayed, or thrown from the crankshaft to the bottom of the pistons.
- Whether it is air-cooled, oil-cooled, or water-cooled, it is the same design. The engine of the locomotive is air-cooled, only the engine of the jet ski is water-cooled.
What is an Air-cooled Engine?
Advantages of air-cooled engines:
- The cylinder of an air-cooled engine transfers most of the heat to the air directly. The metal parts of the engine and is cooled by direct contact with the air.
- Many fins are designed on the cylinder body to increase the surface area of the engine body in contact with the air so that the heat of the engine can be dissipated and then taken away with the air passing through the fins.
- Forced air cooling design: An additional fan is installed next to the heat sink to force an increase in air flow to take away heat.
Disadvantages of air-cooled engines:
- There are a few parts, the structure is simple and not complicated, and the weight is relatively light.
- The cooling system will not fail.
- There is no pump for cooling, so it will not eat up horsepower, which is the most simple and effective design.
- Low cost and convenient maintenance in the future.
- It is difficult to control the ideal working temperature of the engine: the temperature is high when waiting for a red light, and the cooling is fast during travel, resulting in a large temperature difference between the engine's working temperature, so the gap between the parts should be larger to reserve space for thermal expansion and contraction.
- Uneven heat dissipation, this situation is most obvious in multi-cylinder engines.
- Air-cooled engines are limited by the small heat dissipation area. So that higher-performance engines cannot be made.
- When the engine continues to run at a higher temperature, it is more likely that the engine oil will deteriorate faster and the engine parts will be easily worn. Because the air-cooled type must be exposed, the engine noise is also higher than that of the water-cooled type covered by a water jacket. loud.
What is an Oil-cooled Engine?
Disadvantages of oil-cooled engines:
- In addition to air cooling, the original oil is used to enhance the heat dissipation effect of insufficient air cooling.
- The air-cooled engine and the oil-cooled engine with large displacement seem to have only the difference in the size of the oil-cooled exhaust.
- Oil-cooled engines have two sets of oil circuits.
- The structure of the lubricating oil circuit is the same as that of a general engine.
- The cooling oil circuit is dedicated to cooling around the spark plug, and the two brown objects in the cylinder head are where the cooling oil circuit cools the top of the combustion chamber.
- Because there is a cooling oil circuit, it is called an oil-cooled engine, which is essentially an air-cooled engine.
- Using the original oil and oil pump, without adding too much weight, you can get a better heat dissipation effect than an air-cooled engine.
- The heat dissipation effect is obvious, the failure rate is low, and the low temperature of the oil can reduce the viscosity of the oil at high temperatures.
- Disadvantages of oil-cooled engines.
- There is a limit to the amount of engine oil, and the oil radiator should not be too large. Excessive oil will flood into the oil radiator and cause insufficient lubrication at the bottom of the engine.
What is a Water-cooled Engine?
Advantages of water-cooled engines:
- Water's large specific heat, heat conduction properties, viscosity, stability, cost, etc., are suitable as a cooling medium in fluids.
- In the water-cooled engine, the design of cooling water channels is added around and above the combustion chamber. Water is used as the transfer medium to transfer the heat to the cooling water tank, and finally to the air.
- The focus of increasing the heat dissipation area is the heat dissipation water tank.
- The heat dissipation water tank is densely covered with heat sinks. The advanced water tank even uses copper, which has a better heat conduction effect and maximizes the efficiency of heat conduction and heat convection.
- No matter what the form of the engine is, if the cooling water tank is properly designed and placed in the most ideal position against the wind, it can achieve an average and efficient cooling effect.
- The water-cooling system is mostly designed with thermostats, auxiliary fans, and other equipment to maintain a relatively average water temperature, which can keep the engine operating temperature within the most appropriate range.
Disadvantages of water-cooled engines:
- Good cooling effect.
- The shape design of the cooling water tank has a high degree of freedom, and it also gives more flexibility to the design of the model.
- Maintain the engine operating temperature in the most appropriate range, suitable for high-performance engines.
- The cost is high, the structure is complex, and the failure rate is high because the external water tank occupies a large space.
- The water pump, cooling water tank, pipeline, cooling water, etc. increase the complexity and weight of the machine parts, making the water-cooling system have many possibilities of failure.
The Structure of the Engine Cooling System:
- Water tank cover: It is a pressure type, which can increase the boiling point of cooling water without causing vapor resistance and affecting the circulation of cooling water. Check whether the rubber gasket of the water tank cover cannot be hardened and damaged and whether the pressure spring can function normally.
- Anti-rust agent: It can prevent rust in the water jacket and the water tank, and prevent the cooling water in the water tank from freezing and breaking the water tank when the weather is hot and cold. When using, pay attention to the instructions, because some rust inhibitors are not suitable for aluminum alloy cylinder heads or engines. The general color is green, which is convenient for driving to check whether there is water leakage.
- Water tank: The water tank core and heat sink are made of copper and platinum. When the cooling water flows through the water tank core, the air flows through the heat sink to take away the heat by convection.
- Water pump: Driven by the engine mechanically, it forces the cooling water to flow, and presses the cooling water in the water jacket of the engine to the water tank to achieve heat dissipation.
- Thermostat: It is installed on the water outlet of the cylinder head, which can control whether the circulation of cooling water flows through the water tank. When the water temperature reaches the working temperature, it will start to circulate the water, so that the cold engine can quickly reach the working temperature.
Several Engine and Cooling System Issues that Drivers Should be Aware of:
- What are the possible reasons for the overheating of gasoline engines?
Engines often overheat, what could be the cause?
- The cooling system does not work well.
- The ignition timing is not accurate.
- Improper use of hot and cold types of spark plugs.
- Poor engine oil.
- The mixture is too lean.
- Carbon deposits in the combustion chamber.
- The exhaust system is blocked.
- Failures other than the engine part
The cooling water in the water tank will be lost and it needs to be replenished frequently. Is it normal?
- The ignition timing of the engine is incorrect.
- Insufficient cooling water.
- The fan belt slips or breaks.
- The core of the water tank and the heat sink is covered with sand, dry leaves, insect corpses, etc., which will affect the airflow.
- The thermostat fails to open normally.
- Excessive accumulation of scale in the water tank and water jacket affects the cooling water circulation.
- Water pump failure.
- The exhaust pipe is blocked.
- Insufficient oil.
The circulation of cooling water in the water tank is closed, so there is little chance of loss. When the temperature of the engine increases, the pressure and volume of the cooling water in the water tank will increase, and the cooling water will overflow from the overflow next to the water tank cover. The pipe flows into the auxiliary water tank. When the temperature of the engine decreases, the cooling water shrinks, a vacuum is generated in the water tank, and the water in the auxiliary water tank is sucked into the water tank. This is a constant effect. Therefore, only the auxiliary water tank can evaporate. But the amount is small. If it is abnormal to replenish cooling water frequently, it means that there is leakage in the cooling system, and should be checked in detail to find out the location of the leakage and repair it.