What if the coolant reservoire is full and it doesnt drain?

If the coolant reservoir is full and does not drain, it could indicate a blockage in the cooling system or a malfunctioning component, such as a stuck thermostat or a failing water pump. This situation can lead to overheating, as the engine may not be receiving the necessary coolant flow. It's essential to inspect the system for any obstructions or defects and address the issue promptly to prevent potential engine damage. Consulting a mechanic for a thorough diagnosis is advisable.