How does a radiator cap work ?
A radiator cap, known as a radiator pressure cap, is part of the radiator included in the engine cooling system. Generally, we can see the radiator cap on top of the radiator. It is attached to the upper tank or in the inlet tank of the radiator. In some cars models, the radiator cap is attached separately, but it has the same function and operation.
For some people, a radiator cap is only a cap. Still, as a system, the radiator cap holds an important function to the cooling system as a whole. The radiator cap has some value printed on the top, such as 0.9 Kpa or 1.0 bar. This value means the maximum pressure can hold by the radiator cap.
When we want to change the radiator cap, we have to see this value and buy the radiator cap with the same pressure value. Getting pressure values above or under the exact value will ruin the cooling system performance. Your engine would be overheating, or some cooling system parts will get overpressure and blown out.
This post will inform you about radiator cap function and how does a radiator cap work? See the detailed information below.
I. Radiator cap function
Before we jump into how a radiator cap works, we should know what the main function of the radiator cap is. So here are the radiator cap function for the entire cooling system.
A. To close the filler hole of the radiator
The first function that we have already known for the radiator cap is to close the filler hole of the radiator. Closing the hole will prevent the amount of the coolant volume, so the coolant is always at the same amount in every condition. On the other side, the radiator cap allows us to check the coolant volume or add and fill the coolant periodically by opening or closing it.
B. To maintain the pressure inside the cooling system
The second function of the radiator cap is to maintain the pressure inside the cooling system (That's why the radiator cap is known as the radiator pressure cap). It is the main function of the radiator cap for the cooling system. The heat generated by the engine will absorb by the coolant.
As the heat rises, the coolant is getting steamed and boiled. If the coolant gets steamed and boiled, the pressure inside the cooling system also arises. The uprising pressure without any control will damage the entire cooling system.
The cooling system needs a well-maintained pressure to reduce the coolant becoming steaming and boiling. By adding a radiator pressure cap, the system could maintain pressure and avoid the coolant becoming boiled or steamed. So how does a radiator cap work?
Read also:II. How does a radiator cap work ?
As we mentioned before, the radiator pressure cap has a main function to maintain the pressure inside the cooling system.
When the pressure is too high, the radiator cap will let the overpressure pass through the reservoir tank. If the pressure is too low, the radiator cap will let the coolant from the reservoir tank flow into the cooling system.
Generally, the radiator pressure cap has two valves as the main part. The first, pressure valve and the second is the vacuum valve.
A radiator cap pressure valve is used to release the overpressure from inside the cooling system to the reservoir tank. We can see the maximum pressure for the pressure valve on top of the radiator cap and printed liked 0.9 Kpa or 1.0 bar. It means the pressure valve can keep the pressure inside from 0 to 0.9 Kpa or 1.0 bar.
When the coolant is getting hot, it raises pressure. Suppose the pressure is over the max pressure on the radiator cap. In that case, the radiator cap pressure valve will open and let the pressure flow over and go through the reservoir tank. See the images below for the opening pressure valve.
Suppose the pressure in the cooling system is going down, or it is below the max pressure of the radiator cap pressure valve. In that case, the valve will close the path of the coolant.
Meanwhile, when cooling systems are less pressure, such as lower coolant volume or a cold outside temperature. As the engine rotation, and the coolant starts to circulate (pumping by a water pump). The cooling system pressure is getting in vacuum condition.
In this condition, the radiator cap vacuum valve will open and suck the coolant inside the reservoir tank. The coolant will flow through the radiator cap vacuum valve and get inside the main cooling system.
With the valves on the radiator cap, the pressure inside the cooling system will maintain at the normal working pressure and ensure the cooling system's good performance.