Q: antifeeze to come out of the O2 sensor

Hello, thank you for writing in. When coolant leaks into the engine from a blown head gasket, cracked head, crank case, intake manifold, or simply dripping down the engine. If there is actual coolant dripping from the O2 sensor, and none coming from the tail pipe, then you can assume your catalytic converter is likely going to fail soon. It is absorbing the extra coolant and is going to fail soon. This can be a serious issue, and you need to make sure if the vehicle must be driven that it has coolant or water in the cooling system. In winter months, do not keep water in the engine. You must find the source of the coolant leak.