Hi lucky bro. What’s up?
What you are trying to say here is that the level is low in radiator meaning that it’s low in the expansion tank ( Plastic bottle showing coolant level).
Reasons, if you have recently changed the coolant (and there is no leakage) then the system was not properly “burped” ( air released), which has happened now and you just have to top up.
Always when coolant is replaced, ensure that all air in the system has been vented and the system is free of trapped air. Next, keep an eye on the water level for the next 2 to 3 days every time you drive the car and top up if necessary.
Also, I hope you have operated the A/C heater and flushed the coolant at the heater coil and it’s lines during coolant replacement.
Note: Air trapped at the water pump is bad for the pump and should be released/vented,
Always top up water in expansion tank and maintain it between the upper and lower mark when engine is cold.
If all above have been done and still you find low water level in expansion tank then there is a water leak from the system.