Why does the water tank freeze?
Use tap water as the heat transfer medium for the truck's cooling system. Since the freezing point of water is 0℃, when the temperature drops below 
zero, the water tank and other parts of the cooling system are prone to freezing.
To ensure that vehicles can operate normally in winter, antifreeze coolant is now added, which is a type of coolant with antifreeze function. It is generally composed of water, antifreeze and additives. Among them, the largest proportion is still water, because water has a large specific heat capacity and fast heat conduction, and it is easy to dissipate heat after absorbing it. However, after adding a certain amount of antifreeze, the freezing point of the coolant can be lowered.
But sometimes, even though antifreeze coolant with a sufficiently low freezing point has been added, why does the radiator still freeze? This problem is actually quite easy to explain. Coolant is bound to evaporate during daily use, and this is more obvious in the hot summer. Some truck drivers, upon noticing that the coolant level is insufficient, will add some tap water as an emergency measure. However, when water is added to the coolant, its concentration will become thinner. Over time, the anti-freezing performance will be somewhat lost, which will cause the freezing point of the coolant to rise and it will be unable to withstand severe cold weather, unless the car is never turned off.
What should be done if the coolant freezes?
If this situation occurs, first of all, we cannot start the engine, because the freezing of the radiator means that the coolant in the entire cooling system pipeline has solidified. Starting the vehicle rashly can damage the water pump and belt, causing the cooling system to fail to work properly. A malfunction of the cooling system will subsequently cause the engine to overheat and result in cylinder sticking.
Then, it is necessary to carefully inspect the condition of the water tank and pipelines. If the freezing is severe and causes the water tank and pipelines to burst, it is necessary to call maintenance personnel to replace the parts. If all components are found to be in good condition after inspection, the coolant can be thawed by yourself.
The simplest way to defrost the coolant is to "expose it to the sun". Place the vehicle under the sun and let the sunlight shine naturally. After the coolant absorbs heat and its temperature rises, it will return to a liquid state. But what if you are in a hurry to use a car, or if it's still dark and the sun 
hasn't risen yet? At this point, you can pour warm water over the outside of the water tank, wrap the cooling pipes with a hot towel, and heat the frozen coolant.
When the coolant thaws and the engine and cooling system can operate normally, it doesn't mean the problem has been solved. If the coolant with a lower freezing point and a higher grade is not replaced in time, the vehicle will still freeze after being parked and turned off in extremely cold weather.
To prevent the recurrence of coolant freezing, we should replace the coolant in a timely manner that is suitable for the local ambient temperature before winter comes. If we wait until the coolant freezes to replace it, the repair cost of the damaged parts is likely to be higher. Under normal circumstances, the type of coolant is selected based on the temperature of the area where it is located. It is recommended to choose a coolant with a freezing point 5℃ to 10℃ lower than the lowest temperature of the area.
