Have you ever considered the thousands of times explosions occur in your engine? If you’re like most people, that thought never enters your mind. Every time a spark plug fires, the fuel and air mixture in that cylinder blows up. It happens hundreds of times per cylinder per minute. Can you imagine how much heat that generates?
Those explosions are relatively small, but in sheer quantity they produce extreme heat. Consider an ambient air temperature of 70 degrees. If an engine is 70 degrees “cold,” how long after it’s started is the whole engine at running temperature? It only takes a few minutes of idling. How do you get rid of the excess heat created in the combustion process?
Your car engine must be cooled continuously to avoid overheating. There are several methods of doing this. The first and most common of them is the liquid coolant system. This works by circulating coolant, which is usually a mixture of water and anti-freeze, through special cooling passages. Whatever coolant is used, liquid cooling systems have the engine block and cylinder head connected by cooling channels. At the top of the cylinder head, all of the cooling channels end up at a single outlet, which then seeps into the engine. As the used up, hot coolant is pumped out of the engine and into the radiator, where it is taken and cooled again. Thus the cycle repeats.
The pressure in the engine is regulated by the radiator cap, which features a built-in pressure valve. Once that mechanism is tripped, the added coolant creating the pressure is pumped through an overflow pipe. In newer cars, that coolant is sent to a reservoir expansion tank where it cools, and is sucked back into the engine to be re-used in the cycle.
In a nutshell, the water pump pulls coolant from the radiator and pushes it through the system to the engine. The coolant flows through the engine, picking up the heat that the engine is giving off. From there it goes through the thermostat (which controls the amount of flow of coolant) into the radiator. As the coolant flows through the radiator, it is spread out, and has air blown on it by the fan. The liquid is now cool again, sent back to the water pump, and the whole process begins again. Depending on the system, coolant will also flow through the heater core during the cycle to provide heat to the cabin of the vehicle. This does not affect the engine cooling process.
When this process breaks down, the engine will start to overheat. If ignored, the engine will seize and do major damage. Essentially, the vehicle will need a new engine. In older cars, it is often not worth fixing. Needless to say, overheating the engine is one of the worst things you can do to your vehicle.