Why is your coolant bubbling on your 2000 Ford Expedition?

Bubbling coolant in your 2000 Ford Expedition could indicate several issues, such as overheating, a blown head gasket, or air trapped in the cooling system. Overheating can cause coolant to boil and create bubbles, while a blown head gasket may allow combustion gases to enter the cooling system, leading to bubbling. Additionally, insufficient coolant levels or a malfunctioning thermostat can contribute to this problem. It's important to diagnose the issue promptly to prevent further engine damage.