Inside the car engine, there are usually four to six separate cylinders inside which gasoline is constantly burning with oxygen as the spark plugs ignite the fuel in each cylinder to propel the vehicle down the road.
The temperature will be around 2500°C. This is a very high temperature and may result into burning of oil film between the moving parts, and can cause head gaskets to blow and even engine blocks to crack.
So, this temperature must be reduced to about 150-200°C at which the engine will work most efficiently.
It’s the job of the cooling system to take care of that heat and keep the engine from overheating by transferring heat from the engine into the vehicles interior or the atmosphere using heat exchangers called radiators.
The cooling system must work in all operating conditions, adjusting to changes in engine load, vehicle speed and outside temperatures to keep the engine at a constant temperature.
In this article we will see how a car engine cooling system works
Working Principles of the Cooling System
The modern cooling system has not changed much from the ones used in the earlier cars back in the ’20s. It has become more reliable and efficient at doing its job, but the basic principles are still the same.
Although Air cooled engines can be found on a few older cars, almost all automobiles’ internal combustion engines are fluid cooled using a liquid coolant that runs through a radiator cooled by air.
By passing the liquid coolant continually through the passages in the engine block, it absorbs heat from the engine. The heated liquid then travels to the radiator, where it is cooled by the air stream entering the grille of the car.
Cooling System Parts
1) Water Pump
Water pump is the heart of the cooling system which pumps the coolant, and as explained in a previous article, the main components of a water pump include housing, hub, bearings, gasket, impeller, and seals.
Water pump uses an engine-driven impeller to draw the coolant from the radiator and pump it into a safe passage through which the coolant can flow without entering into the cylinder or mixing up with the oil. This passage is known as water jacket.
As the coolant moves through the engine, heat from combustion transfers into the coolant, reducing combustion chamber temperature
The coolant in today’s cars is a mixture of ethylene glycol (antifreeze) and water, with a recommended ratio of one part antifreeze and one part water. This is the minimum recommended for use in automobile engines.
The coolant helps prevent corrosion in the cooling system, and also carries away the engine’s waste heat.
A radiator, consisting of many small tubes equipped with a honeycomb of fins to radiate heat rapidly, receives and cools hot liquid from the engine; it acts as a heat exchanger to dissipate engine heat from the coolant to the air, sending excessive heat into the outside air.
The radiator has an inlet port, an outlet port, a drain plug, and a radiator pressure cap. The radiator cap is designed to release pressure if it reaches the specified upper limit that the system can handle.
Radiators are prone to leaking after years of use
The Thermostat is a temperature controlled valve. When the engine is cold, the thermostat stays closed to prevent coolant flow. As the engine warms up, the thermostat opens to allow coolant flow and controls flow to maintain a target temperature.
Since the 70s, thermostats have been calibrated to keep the temperature of the coolant above 192 to 195 degrees.
The thermostat needs to be replaced from time to time. It’s easy to diagnose a failed thermostat and is inexpensive to replace.
Cooling system hoses provide a path for the coolant as it travels between different parts. They use rubber and fabric construction to help isolate engine vibration from the external components. Because of this, hoses require regular inspection for wear, leaks, and damage.
6) Radiator Fan
Mounted on the back of the radiator, on the side closest to the engine, is one or two electric fans inside a housing that is designed to protect fingers and to direct air flow.
Radiator fan turns on when the temperature of the coolant goes above a set point and turns back off when the temperature drops below that point.
Front-wheel drive cars have electric radiator fans that are controlled by the engine computer, while rear-wheel drive cars usually have engine-driven cooling fans that have a thermostatically controlled viscous clutch.
How Often Should I Check My Cooling System?
Cooling systems fail more often than any other mechanical system – usually because of neglect, but if you take care of your cooling system it can keep working for the life of your car.
Common signs of a cooling system issue include white smoke coming from under the hood, the dashboard temp gauge rising or a visible coolant leak. The most important maintenance item is to flush and refill the coolant periodically.