Now that we are in the middle of the dog days of summer, and temperatures are reaching all-time highs in most of the northern hemisphere it is a good time to touch on the classic car cooling system basics.
The car cooling system serves three essential functions. First, it removes excess heat from the engine; second, it maintains the engine operating temperature where it works most efficiently; and finally, it brings the engine up to the right operating temperature as quickly as possible.
The engine in your car works best at a reasonably high temperature. When the engine is cold, components wear out easily, emits more pollutants, and the engine becomes less efficient. Thus, another important task of the cooling system is to allow the engine to warm up as quickly as possible, and then to maintain a constant engine temperature. The main function of a cooling system is to ensure that the engine runs at its optimum operating temperature. If the cooling system or any part of it fails, it will overheat the engine, which can lead to many serious issues.
Have you ever imagined what would happen if your engine cooling system did not work properly? Overheating can cause cylinder head gaskets to explode and even crack engine blocks if the problem is serious enough. And all this heat must be fought. If the heat cannot be removed from the engine, the pistons are welded to the inside of the cylinders. Then you just must throw the engine away and buy a new one. So, you should take care of your engine cooling system and learn how it works as it is more than just adding fluids to your radiator.
The Radiator as The Primary Part of the Car Cooling System
A radiator is a type of heat exchanger. It is designed to transfer heat from the hot fluid that flows through it to the air blown through it by the fan.
Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant fluid flows from the inlet to the outlet through many tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.
The tubes sometimes have a type of fin inserted into them called a turbulator, which increases the turbulence of the fluid flowing through the tubes. If the fluid flowed very smoothly through the tubes, only the fluid touching the tubes would be cooled directly. The amount of heat transferred to the tubes from the fluid running through them depends on the difference in temperature between the tube and the fluid touching it. So, if the fluid that is in contact with the tube cools down quickly, less heat will be transferred. By creating turbulence inside the tube, all the fluid mixes together, keeping the temperature of the fluid touching the tubes up so that more heat can be extracted, and all the fluid inside the tube is used effectively.
Radiators usually have a tank on each side, and inside the tank is a transmission cooler. In the picture above, you can see the inlet and outlet where the oil from the transmission enters the cooler. The transmission cooler is like a radiator within a radiator, except instead of exchanging heat with the air, the oil exchanges heat with the fluid in the radiator.
How Does a Car Radiator Work?
A radiator has a number of flat and thin pipes arranged horizontally one below the other, or vertically in the older vintage cars. Water flows through these pipes along their length. But how does the fluid flow through these pipes gets cool so fast? So, to increase the heat exchange from liquid coolant to air, we have fins brazed between the flat surfaces of these pipes. These fins between the pipes look like a dense sine wave (trigonometric function). Thus, increasing the surface area that encounters air and increasing the heat exchange.
Is it all we have in a radiator to exchange heat? Then no, we are not done yet.
High-end car radiators are a bit more sophisticated; we have fins like structures inside the radiator pipes. These are added to create turbulence in the water flowing through them. The water flowing through pipes without internal fins is streamline. Thus, the heat exchange will be between the outer layer of coolant and the air. As the outer layer of water gets cooler, it is reducing the temperature difference between air and coolant as a result, the rate of heat exchange will decrease.
Whereas in the radiator pipes with internal fins, water molecules that exchange heat with air get mixed up with hot coolant, due to turbulence created by these fins. Thus, keeping the temperature of the whole coolant uniform and high. In this way, a greater amount of heat could be exchanged, and coolant gets cooler at a really very fast pace. The key to moving air across your radiator for cooling is the fan your car uses to pull or push the air thru your classic car’s radiator.
What Is the Function of a Pressure Cap On a Radiator?
Temperature of engine goes much higher than 100 degrees centigrade, and water is used as a coolant in cars. But the water starts boiling at 100 degrees and gets converted into steam. And steam does not exchange heat at a good pace. So how water can be used as a coolant.
To solve this problem pressure caps are introduced in a radiator. Pressure cap does not allow the pressure formed in the radiator to escape created by hot water coming from the engine. Thus, there is an increase in pressure inside radiator as water gets hotter. And as we know that the boiling point of a liquid increases if it is heated at a higher pressure. So, pressure cap increases the boiling point of water and keeps it in liquid state even at temperatures higher than 100 degrees centigrade.
Imagine if pressure in the radiator goes on increasing it could bust the radiator pipes, to short out this problem, pressure cap is equipped with a spring at its bottom, which gets lifted up as the pressure reaches around 15psi, so pressure cap acts as a valve and releases the pressure to overflow tank when it exceeds the limit of 15 psi.
We have discussed the types of engine coolant (anti-freeze) that are available and the importance of keeping the proper level as well as the proper mix in your cooling system to prevent your car from over-heating. By utilizing the proper coolant additive to your cooling system, the boiling point is again increased to improve the cooling capability of the cooling system at work.
Transmission Fuid Cooling
Ever heard of transmission oil used in gearbox and power-steering going into the radiator. In high payload vehicles, we must cool down the transmission oil and we use our radiator to remove the heat from this oil. The side of the inlet port of the radiator is called hot side as hot fluid from the engine enters from this side, as liquid coolant moves through pipes and gets cool and gets out of the radiator through outlet port called cold side. So, we have a cylindrical structure on the cool side of the radiator through which transmission oil circulates thus exchanges its heat with cold fluid.
What Happens Inside Cooling Systems at Work?
The cooling system works by constantly passing coolant fluid through channels in the engine block. Coolant, driven by a water pump, is pushed through the cylinder block. As the solution passes through these channels, it absorbs heat from the engine.
Leaving the engine, this heated fluid enters the radiator, where it is cooled by the air flow entering through the car’s radiator grill. The fluid will cool as it passes through the radiator, returning to the engine again to pick up more engine heat and carry it away.
There is a thermostat between the radiator and engine. Depending on the temperature, the thermostat regulates what happens to the liquid. If the fluid temperature drops below a certain level, the solution bypasses the radiator and is instead directed back to the engine block. The fluid will continue to circulate until it reaches a certain temperature and opens the valve on the thermostat, allowing it to pass through the radiator again for cooling.
It seems that due to the very high engine temperature, the coolant can easily reach its boiling point. However, the system is under pressure to prevent this from happening. When the system is under pressure, it is much more difficult for the coolant to reach its boiling point. Occasionally, however, pressure builds up and must be relieved before it can deflate the hose or gasket. The radiator cap relieves excess pressure and fluid by accumulating in the reserve tank. After the liquid in the storage tank has cooled to an acceptable temperature, it is returned to the cooling system for re-circulation.
Finally
Keeping the car cooling system in top shape will ensure a longer life for your classic car’s engine. Understanding how the car engine’s coolant system works as well as regular inspections and maintenance are important part of the classic car care ritual. Even though you may not drive your classic car regularly it is important to keep your car cooling system in prime shape. It will also ensure that you will not find yourself stranded on the road with steam gushing from under the hood.
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