Cool It! How Your Car’s Cooling System Works
Ever wonder why your vehicle needs a cooling system? (Sure you do—along with all those other deep philosophical questions we ponder from time to time….)
We all know and love our AC, especially in temps like we’ve been having lately. But your car’s cooling system has nothing to do with its air conditioning. That’s a different type of cooling system.
While your AC is cooling you inside the car, the job of the cooling system is to dissipate the enormous amount of heat generated by the burning of the gasoline. The cooling system on a car driving down the highway, for example, cools enough thermal energy to heat two average-sized houses!
So the cooling system’s job is to keep your engine from overheating by transferring this heat to the air. And it has several other jobs as well, including allowing the engine to heat up as quickly as possible and then keep it at a constant temperature, to ensure that the combustion chamber is hot enough to completely vaporize the fuel. This provides better combustion, reduces emissions, and keeps the oil at a lower viscosity (i.e., thinner, so it lubricates better, engine parts move more freely, the engine wastes less power moving its components, and those parts sustain less wear).
There are two types of cooling systems found on vehicles: liquid-cooled and air-cooled.
Let’s start at the pump and work our way through the entire system.
• Pump — Sends the fluid into the engine block.
• Engine block — Passes fluid to passages in the engine around the cylinders.
• Cylinder head — After the fluid is dispersed in the engine block, it returns to the cylinder head.
• Thermostat — The plumbing around the thermostat, where the fluid leaves the engine, sends the fluid directly back to the pump if it’s closed. If open, the fluid then goes through the radiator first and back to the pump. It allows the engine to heat up quickly, and then it keeps the engine at a constant temperature by regulating the amount of water that goes through the radiator. At low temperatures, the radiator’s outlet is completely blocked, and all the coolant is recirculated back through the engine.
• Radiator — a type of heat exchanger designed to transfer the heat from the hot coolant that flows through it to the air blown through it by the fan.
• Cooling fan — Like the thermostat, this component must be controlled so it allows the engine to maintain a constant temperature. Fans are controlled either with a thermostatic switch or by the engine computer. They turn on when the coolant temperature goes above a set point and turn back off when it drops below that point.
• Water pump — a simple centrifugal pump driven by a belt connected to the engine’s crankshaft that circulates fluid whenever the engine is running.
In addition to these primary components of your vehicle’s cooling system, there are also a couple of additional parts important to the overall system.
The radiator cap, which sits on top of the radiator, increases the coolant’s boiling point by about 45 degrees Fahrenheit (25 Celsius). It works the way a pressure cooker does, by increasing the boiling temperature of water. When placed under pressure, the boiling point of water increases. The cap serves as a pressure release valve, thus allowing you to safely release the pressure built up in the radiator by the extreme heat. (Note: Never remove a radiator cap when the radiator is hot, or you’ll get a faceful of boiling hot water and anti-freeze.)
The heater core, located in the dashboard, is like a small radiator. The heater fan blows air through the heater core and into the passenger compartment.
Temperatures in the combustion chamber of the engine can reach up to 4,500 F (2,500 C). So cooling the areas around the cylinders and the exhaust valves is critical. And most of the space inside the cylinder head around the valves not needed for structure is filled with coolant. If the engine goes for too long without cooling, it can seize up—which means that the metal has actually gotten so hot that the piston welds itself to the cylinder. This will usually result in the complete destruction of the engine.
So as you can see, your vehicle’s cooling system plays a vital role in the proper functioning of the engine. Without this complex system of engineering and design principles in place, you’d basically be driving around (not for long) in a thermal mass of metal just waiting to boil over, melt down, and explode. Making sure you have enough coolant is only the first step in responsible cooling system maintenance. Periodic system flushes at regularly scheduled intervals, as well as routine inspection of the components, will keep you driving safely and soundly without any worries.
Have any questions about your cooling system or any other automotive issues? You know who to call. (No, not Ghostbusters — Quality Automotive!)