<human>: What is a blown head gasket and how do you repair it?
<bot>: A blown head gasket is when the rubber or plastic that separates the engine's combustion chambers from the engine block cracks, allowing hot exhaust gases to leak into the coolant system. This causes the engine to overheat and can cause severe damage if not repaired quickly. To fix a blown head gasket, you'll need to replace the entire head gasket assembly including the gaskets and bolts. You may also need to replace other parts of the engine, such as the pistons and connecting rods, depending on the severity of the damage.