What Happens if Your Car Runs Out of Coolant

January 27, 2012

Almost all car engines these days are liquid cooled, meaning that keeping your engine full of coolant is integral to its smooth operation. Letting the coolant level in your car get too low can result in disastrous consequences, so it is important that you keep your coolant level in check regularly. Most cars will help you do this via a gauge on the dashboard.

Cars use engines for power, and engines work at high RPMs to produce that power. High RPMs means more motion and, as elementary physics teaches us, more motion means more heat generated. In order to generate the kind of power needed to move the car, the engine needs to work at a rate that produces higher temperatures than the metal of the engine can handle. If left unchecked, the heat in the engine will build and reach a tipping point, after which the engine is liable to overheat and break down. This is why cooling systems are necessary.

Engines are cooled by a combination of two different methods. One of them is engine oil, which flows through the engine, lubricating and cooling moving parts like the pistons and rods. The other is the coolant system, which cools the cylinder and cylinder heads and parts of the exhaust system. This is the system we will focus on.

The coolant system is basically a big loop through which fluid, usually a mix of water and antifreeze, is  pumped. Regular water would actually do the job sufficiently, but since cars are designed to operate in sub-freezing temperatures, antifreeze is added to prevent the water from freezing and cracking the piping system. The mixture of water and antifreeze is called coolant. Up until several yeas ago coolant came undiluted, and it was the driver or mechanic's job to mix it with water. Nowadays coolant comes pre-mixed.

The job of coolant is to absorb the heat generate by the engine and transport it away, thus keeping the engine cool. In order to avoid creating steam, the coolant must be pumped very quickly. Once the coolant has absorbed heat, it flows to the radiator where it is cooled down. Most cars (rear-engined cars like Porsches and the Toyota MR-2 being exceptions) have the radiator in the front of the car, right behind the grill. The forward movement of the car forces air through the radiator, helping to cool the coolant inside of it so that it can be recirculated. A lower-than-normal level of coolant means that the coolant has less time to cool in the radiator before being pumped through the system again, resulting in inefficient engine cooling.

A radiator full of coolant can mean the difference between getting to your destination safely and breaking down on a country road in the middle of nowhere. As cars get older they may start to leak coolant, and it is important that you regularly check your coolant level. This is one system of your car you want to have in good condition at all times.

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