Why is your anti-freeze overflow full and your radiator empty on your Pontiac Montana?

If the anti-freeze overflow is full while the radiator is empty, it could indicate a leak in the cooling system, possibly due to a damaged radiator, hose, or water pump. Another possibility is that the system may have air trapped in it, preventing proper flow and causing the radiator to drain. Additionally, a blown head gasket could lead to coolant being pushed into the overflow. It's important to diagnose the issue promptly to avoid engine overheating or damage.