Signs of a blown head gasket include engine misfire, motor overheating, and oil in the coolant or coolant in the oil. A blown head gasket does not necessarily manifest all of these symptoms.
Signs of a blown head gasket differ depending on the area in which the gasket is failing. For example, if it is failing between cylinders, the motor may misfire or idle roughly, but the motor does not overheat and no coolant would be present in the oil or the other way around. Symptoms of a blown head gasket can also be an indication of other problems, so additional troubleshooting may be necessary to determine if the head gasket is really blown.