Coolant leakage may occur due to breakage of the head gasket that seals a cylinder head in an engine, or can be due to cracks in the coolant jacket surrounding the cylinder. Both kinds of leaks may cause the engine to gradually lose coolant and eventually overheat, potentially causing severe damage. In addition, coolant leaks due to cracked gaskets or cylinders can allow coolant to leak into other parts of the motor and damage critical components of the engine.
Coolant leaks due to cylinder or gasket cracks are among the most dreaded types of coolant leaks, since they are not usually externally obvious. This gives the leak the potential to persist long enough to dangerously reduce engine coolant levels and cause overheating before there is any sign of a problem. In addition, fixing a cracked head gasket or cylinder leak is often an expensive proposition due to the extensive labor required to find and fix the problem. However, it is possible to repair some leakage issues caused by small cracks, by using a sealant material containing sodium silicate, also known as liquid glass.
Damage from coolant leaks into the interior of the engine often takes the form of corrosion damage. Which parts of an engine are at risk largely depends on whether the leak is due to a cracked gasket or cracked cylinder. Gasket cracks can allow coolant to dilute oil and foul spark plugs, resulting in white smoke and bearing damage. Cracks in a cylinder cooling jacket can allow coolant to damage the pistons, cylinder rings, or even the crankcase of the engine, depending on the location of the leak.