Yesterday afternoon, I took the car out and after driving a few minutes noticed the air over the bonnet shimmering and undulating like in a mirage. I have seen this before and it's not good news. The last time I saw this sign, the car burst into flames, the birds flew away, the sky clouded up and I heard the devil. I quickly parked the car and took a look inside the bonnet. The engine had overheated and was hissing and puffing at the seams. I clearly remember adding any coolant, about four months ago. Understandably, the engine was unhappy about it. when I opened the coolant chamber lid scalding hot fluid gushed out barely missing making a hot meal of my fingers. Luckily a bottle of water I carry for emergencies was at hand. I emptied it into the coolant chamber standing as far away from the car as possible, and watched in fascination as the water went in and came right out, and kept doing this for a few times. A geyser.
I no longer have a car (I gave mine up several years ago after moving to a city in France where I simply don't need one), but when I did have one, that happened to me once. In my case, also a disaster. The headgasket blew. The cause was the thermostat had broken, so there was no indication of the temperature; hence, the fan to cool to the water in the radiator never turned on. As far as I can recall, there was no warning before the geyser, albeit afterwards the "oil" idiot light was lit (probably due to losing oil through the blown head gasket). Bletch...!