Final answer:
It is generally not safe to add coolant to a coolant recovery tank or overflow tank while the engine is at operating temperature. When the engine is running, the coolant is hot and under pressure. It is recommended to wait until the engine cools down before adding coolant.
Step-by-step explanation:
It is generally not safe to add coolant to a coolant recovery tank or overflow tank while the engine is at operating temperature. When the engine is running, the coolant is hot and under pressure. Opening the coolant reservoir cap while the engine is hot can cause a sudden release of hot coolant, resulting in burns or injuries. It is recommended to wait until the engine cools down before adding coolant to the tank.
Adding coolant to a hot engine can also cause thermal shock to the engine components, such as the radiator and engine block. This can lead to cracking or damage to these components. It is best to follow the manufacturer's guidelines on when and how to add coolant to the system.