The combustion engine relies on its coolant system to function properly. When it doesn’t, the cylinder head can crack due to heat stress, the differential thermal expansion of metal. Naturally, the fracture occurs between the hot area (combustion exhaust) and cold areas of the cylinder. When the metal cracks between these two areas, coolant can then leak into the cylinder to be combusted along with the fuel mix. The result: white smoke and a new engine. In one of our cases, an engine was being “modified” for racing. The modification somehow failed to account for the purpose of the coolant system as it actually decreased the volume rather than increasing it to absorb the increased heat generated by the higher-powered engine. As a result: insufficient cooling of the cylinders, cracking, and an engineer sent by the insurance company to opine on the matter.