Risk of Scalding: When the engine is running, the coolant in the radiator is at high temperatures. Opening the radiator cap while the engine is running can cause the hot coolant to erupt and spray out, scalding you or bystanders.
Overfilling: If you attempt to fill the radiator when the engine is running, it's more likely to overflow. As the engine runs, the temperature of the coolant rises, causing expansion. If the radiator is already full when the engine starts, the expanding coolant has nowhere to go and will overflow from the radiator cap.
Air Pockets: Adding coolant while the engine is running can introduce air pockets into the cooling system. Air pockets can cause the system to become less efficient at cooling the engine, potentially leading to overheating.
Correct Procedure: The recommended procedure for refilling the radiator or adding coolant is to turn off the engine and allow it to cool down completely. Once it has cooled down, remove the radiator cap (be careful of residual pressure that might cause a small burst of hot coolant) and slowly add the coolant or water according to the manufacturer's guidelines.
Additionally, it's important to check your vehicle's owner's manual or consult a qualified mechanic for specific instructions and recommendations regarding the cooling system and coolant refilling process for your specific vehicle.
By following these guidelines, you can safely and effectively maintain the cooling system of your vehicle.
