* Head Gasket Failure: The head gasket seals the combustion chambers from the coolant passages. If it fails, coolant can leak into the cylinders. When the engine combusts, the pressurized mixture pushes the coolant into the exhaust system.
* Cracked Cylinder Head: A crack in the cylinder head can also allow coolant to mix with combustion gases, leading to the same result – coolant exiting the exhaust.
Less likely, but possible causes include:
* Cracked Engine Block: Although less common, a crack in the engine block could also allow coolant into the combustion chambers. This is a much more serious and expensive problem than a head gasket or cracked head.
* Improper Coolant Mixture: While unlikely to cause a significant leak *into* the exhaust, a severely improper coolant mixture (too much or too little antifreeze) could lead to overheating and potentially damage that would exacerbate a pre-existing problem (like a hairline crack in the head or block).
In short: Seeing antifreeze in the exhaust is a serious problem requiring immediate attention. Continuing to drive the car will cause significant engine damage. You should have a mechanic diagnose the exact cause (head gasket, cracked head, etc.) and perform the necessary repairs.
