Cracked cylinder head, or more commonly, a corroded head gasket. Coolant gets sucked into a cylinder as it tries to draw in fresh air. The piston pushes the air, fuel, and coolant out through the exhaust valve through the exhaust system, to the tail pipe.
A cylinder leak test can be used to identify which cylinder has the leak. Compressed air is forced into the spark plug hole while that piston is at top dead center. The air will be observed leaking out in one of four places:
1. Tail pipe - exhaust valve
2. Air intake - intake valve
3. Oil fill cap - piston rings
4. Bubbles in radiator - head gasket / cracked head
Sunday, March 7th, 2010 AT 11:54 AM