Human: What is a blown head gasket and how do you repair it? Assistant: 
A blown head gasket is caused by a failure of the engine's head gasket. This can cause serious engine damage, as coolant leaks out of the engine and causes overheating and other issues. The first step to take when diagnosing this issue is to check for any visible signs such as smoke coming from the engine or oil leaking from the engine. If there are no obvious signs, you should consult a mechanic who can inspect your vehicle further and determine if the head gasket needs to be replaced or repaired.