After a surprisingly short period of time, I found out what happened to my car when it broke down a couple of days ago.
As it turned out, the thermostat which regulates the cooling system went bad. What happened was that the thermostat erroneously decided to start reading MAXTEMP (which would mean that the engine block was about to melt down); it dutifully sent these messages to the microprocessor controlling the engine. The CPU erroneously decided that the cooling system had fouled up in some unspecified manner and commanded the water pump to start feeding coolant to an overflow bottle in an attempt to lower the amount of coolant circulating, thus relieving internal pressure (which didn't actually exist). When the coolant overflow bottle filled up an emergency valve began flapping open and closed, spraying water, coolant, and who knows what else all over the inside of the engine compartment. Due to the fact that a MAXTEMP situation wasn't actually happening, this only served to drain the cooling system, which impaired the engine's efficiency (because it started to overheat due to the lack of coolant) and caused a breakdown. The garage replaced a gasket and the thermostat, refilled the coolant, and so far as I can tell, all is operating normally.