What is Cooling System?- Types, and How it Works

When your engine doesn’t cool down properly, bad things happen. Parts wear out faster, more nasty stuff gets released into the air, and worst of all, your engine becomes less efficient.

That’s why the cooling system is super important. It’s like a superhero that swoops in to save the day by getting your engine toasty and keeping it that way.

The cooling system’s job is to make sure your engine stays at the perfect temperature. If any part of the system fails, your engine can get too hot and that’s when the trouble begins.

Head gaskets explode, engine blocks crack and all that heat can even make the pistons stick to the cylinders. Ouch! Trust me, you don’t want to be in that situation. It’s like saying goodbye to your engine and shelling out for a new one.

So, it’s crucial to take care of your engine cooling system and understand how it works. Treat it right, and it’ll keep your engine cool and happy for miles and miles.

What is a cooling system?

A vehicle’s engine-cooling system not only keeps the engine cool but keeps its temperature warm enough to ensure efficient, clean operation.

System components include a radiator to remove heat, a fan or fans to ensure adequate airflow for radiator cooling and a thermostat valve that opens when the desired operating temperature is reached and circulates coolant through the engine.

To do this a water pump (or coolant pump) is included. and other components. Most vehicles now use an expansion tank that allows coolant to expand and exit the cooling circuit when it is hot, and when the car is stopped and the engine is cold.

The cooling system also includes elements of the cabin ventilation system, as engine heat is used to heat the car interior.

How does a car cooling system work?

The cooling system is a system of parts and fluid that work together to control an engine’s operating temperature for optimal performance.

The system is made up of passages inside the engine block and heads, a water pump and drive belt to circulate the coolant, a thermostat to control the temperature of the coolant, a radiator to cool the coolant, a radiator cap to control the pressure in the system, and hoses to transfer the coolant from the engine to the radiator.

The liquid that flows through a cooling system, antifreeze, or commonly referred to as coolant, withstands extreme hot and cold temperatures and contains rust inhibitors and lubricants to keep the system running smoothly.

Coolant follows a circulation path that begins with the water pump. The water pump’s impeller uses centrifugal force to draw coolant from the radiator and push it into the engine block. Pumps are usually fan, serpentine timing belt, or timing chain driven.

Nowadays, they may even be driven electrically. If the water pump experiences a leak from the seal, a cracked housing, broken impeller or a bearing malfunction, it can compromise the entire cooling system, causing the vehicle to overheat.

As coolant flows through the system, it picks up heat from the engine before arriving at the thermostat. The thermostat is a valve that measures the temperature of the coolant and opens to allow hot fluid to travel to the radiator.

If the thermostat becomes ‘stuck’ and quits working, it will affect the entire cooling system. Once released by the thermostat, hot coolant travels through a hose to be cooled by the radiator. The antifreeze passes through thin tubes in the radiator.

It is cooled as air flow is passed over the outside of the tubes. Depending upon the speed of the vehicle, airflow is provided by the vehicle’s movement down the road (ram air effect) and/or cooling fans. Radiator restrictions can compromise its ability to transfer heat. These can be either external air flow or internal coolant flow restrictions.

A malfunctioning electric cooling fan or fan clutch can limit air flow across the radiator. Check/replace the fan clutch…the life expectancy of water pumps and fan clutches are about the same and share a common shaft.

A failed fan clutch can cause severe damage to the water pump. As coolant temperature increases, so does the pressure in the cooling system. This pressure is regulated by the radiator cap. Correct system pressure is required for proper water pump seal lubrication.

Increasing the cooling system pressure raises the boiling point of the coolant. Each one pound of increased pressure raises the boiling point by 3˚F. If the pressure builds up higher than the set pressure point, a spring-loaded valve in the cap will release the pressure.

If an engine has overheated, the radiator cap and thermostat should be replaced. It is important to regularly inspect the condition of your cooling system’s belts and hoses. Soft hoses, oil soaked belts or cracked belts and hoses can have dire effects on the entire cooling system.

Proper belt tension is also important. Always refer to your manufacturer’s manual to determine the recommended coolant type for your vehicle. This and the proper mixture of coolant and distilled water are the lifeblood towards keeping your system running cool.

Most parts retailers now offer a solution of premixed coolant and distilled water. While it may seem like an unnecessary added expense, the cleanliness of the premixed solution will pay off over time. Mineral deposits and sediments from corroded or malfunctioning parts accumulate in the cooling system.

Before performing a cooling system repair, it is recommended to flush the cooling system prior to installing any new parts. This is a task made even easier by using a flush-fill kit. Failure to flush the system will contaminate the new parts being installed and could lead to premature component failure.

the Parts of Cooling System

The major components of the cooling system are the water pump, freeze plugs, thermostat, radiator, cooling fans, heater core, pressure cap, overflow tank, and hoses.

#1. Cooling Fan.

The cooling fan is located at the very front of the vehicle and is designed to turn on when the coolant (we’ll talk more about this in a minute) begins to get too hot. It will turn back off once the coolant has lowered in temperature.

#2. Radiator.

Heated coolant flows into the radiator inlet, is passed through a series of tubes and fins that effectively dissipate heat from the coolant.

#3. Water Pump.

The water pump is considered the ‘heart’ of the cooling system and is usually located on the front of the cylinder block. A hose carries cooled coolant from the radiator to the water pump.

A belt or chain turns the water pump shaft and coolant enters the center of the pump. The water pump has fan-like blades on an impeller that spins, creating centrifugal force, moving the liquid outward.

Coolant is routed through the engine, cylinder heads and intake manifold by way of water jackets. The coolant then absorbs heat from the engine components and, once hot, leaves the engine and enters the radiator once again to begin the next cooling cycle.

#4. Belts.

Whether it is a timing belt or an accessory drive belt, belts are often the driving link which turns the water pump. Timing chains sometimes perform the job of driving the water pump instead of the belt.

They must always be in good condition and have the proper amount of tension to turn the pump at the correct speed and to avoid engine damage due to misaligned internal engine components.

#5. Radiator Cap.

The radiator cap is responsible for maintaining the proper amount of cooling system pressure. If the amount increases above the set pressure point, a spring-loaded valve in the cap releases extra pressure.

#4. Thermostat.

The thermostat regulates the flow of coolant into the engine keeping it at its optimum operating temperature. The thermostat is closed when the engine is cold. As the engine heats up, the thermostat opens and allows coolant from the radiator to circulate.

#5. Hoses.

Hoses carry coolant to and from the radiator and heater core assembly. Hoses that are spongy to the touch or that have cracks present should always be replaced.

#6. Antifreeze/Coolant

As coolant, or antifreeze, flows through a hot engine, it absorbs engine heat to be dissipated in the radiator.

Most coolant contains anti-rust and corrosion additives that prevent sediment build-up and premature cooling system component failure. Coolant comes in a variety of colors and formulas. Always use the formula and mixture recommended by the vehicle manufacturer.

#7. Fan Clutch.

The fan clutch engages as needed to draw air through the radiator. It allows the fan to free-wheel when air is not needed thus reducing horsepower loss and improving fuel efficiency. Note: not all vehicles are equipped with a fan clutch.

#8. Freeze Plug.

Is actually a steel plug designed to seal holes in the engine block and cylinder head(s) created from the casting process. In freezing weather they may push out if there is not enough anti-freeze protection.

#9. Head Gasket /Timing Cover Gasket.

Seals the major parts of the engine. Prevents oil, anti-freeze and cylinder pressure from mixing together.

#10. Heater Core.

Provides heat to the interior of the car by using heat removed from the antifreeze and blown in by the blower motor. May cause steam, odor or actual dripping inside the car when it leaks.

The Necessity of Cooling System

The cooling system serves three important 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 need of cooling systems in an IC Engine because of the following reason:

• During the operation of an engine, the temperature inside the engine can go up to 2500 degrees centigrade (Source: How Stuff Works), which is above the melting point of the components used to make the engine. So, we need to use the cooling system to dissipate the heat as much as possible.
• As we know, we also need a lubrication system for the proper functioning of the engine, but due to the high heat, the property of lubricating oil can be changed. That result seized the engine. So to avoid that we need to use a cooling system.
• Sometimes due to the enormous heat, thermal stress is built-up inside the engine, so to minimize the stress we need to keep the engine temperature as low as possible.

Types of Engine Cooling Systems

Generally, there are two types of cooling systems, and those are:

• Air Cooling System
• Water Cooling System

1. Air Cooling system

Air cooling is a method of dissipating heat. It works by expanding the surface area or increasing the flow of air over the object to be cooled, or both. The addition of fins to a heat sink increases its total surface area, resulting in greater cooling effectiveness.

An example of the former is to add cooling fins to the surface of the object, either by making them integral or by attaching them tightly to the object’s surface (to ensure efficient heat transfer). In the case of the latter, it is done by using a fan blowing air into or onto the object one wants to cool.

There are two types of cooling pads used in air cooling one is a honeycomb and another one is an excelsior.

In all cases, the air has to be cooler than the object or surface from which it is expected to remove heat. This is due to the second law of thermodynamics, which states that heat will only move spontaneously from a hot reservoir (the heat sink) to a cold reservoir (the air).

When operating in an environment with lower air pressure like high altitude or airplane cabins, the cooling capacity has to be derated compared to that of sea level.

A rule-of-thumb formula 1 – (h/17500) = derating factor. Where h is the height over sea level in meters. And the result is the factor that should be multiplied by the cooling capacity in [W] to get the cooling capacity at the specified height over sea level.

Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures.

In all combustion engines, a great percentage of the heat generated (around 44%) escapes through the exhaust, not through the metal fins of an air-cooled engine (12%).

About 8% of the heat energy is transferred to the oil, which although primarily meant for lubrication, also plays a role in heat dissipation via a cooler.

Air-cooled engines are used generally in applications that would not suit liquid cooling, as such modern air-cooled engines are used in motorcycles, general aviation aircraft, lawnmowers, generators, outboard motors, pump sets, saw benches, and auxiliary power units.

Advantages of Air-Cooling System

These are some advantages of using Air Cooling Systems:

• Light in weight
• No antifreeze is required
• This system can be used where water scarcity is there
• Simple in design
• Require less space
• No tapping up of water, etc.
• Prevents Electronics From Overheating.
• Improves Work Performance

Disadvantages of Air-Cooling System

Air-Cooling Systems also have some disadvantages, and those are:

• More noise in operation.
• The coefficient of heat transfer of air is less, hence less efficient in working.

Examples of Air-Cooled Engines:

It is used in scooters, motorcycles, and tractors.

2. Water Cooling System

This type is the most commonly used type of system.

In a water cooling system, water jackets are provided around the engine cylinder or liners. The circulating water in these jackets absorbs the heat from the cylinder surface and then heated water is cooled by the air passing in the radiator.

The water cooling system consists of water jackets, a water pump, a radiator, a thermostat valve, a fan, a belt, and pulley, etc.

Although, water is the most commonly used cooling agent, special coolants having better and desired properties like corrosion-free, higher boiling point, etc. are also available in the market and recommended also for obtaining and marinating higher engine efficiency.

The water is made to circulate in the water jackets continuously with desired pressure and speed with the help of a water pump driven by a belt. Generally, water pumps are of a centrifugal type and consist of a water inlet and outlet with an impeller which makes the water come out from the pump outlet by a centrifugal force.

The pump inlet is connected to the radiator at the bottom to draw the coolant/water from the radiator. When the engine is cooled, the thermostat valve remains open and the same water/coolant is circulated through the water jackets.

By the time, the water/coolant gets heated, the thermostat valve is opened to make water pass through the radiator to dissipate heat by coming intact with the air passing through the radiator.

The radiator is located in the front of the tractor/vehicle and it consists of a water/coolant tank, tubes, and a pressure cap on the tube. This pressure cap is used to prevent water evaporation and increase the pressure within the cooling system.

The temperature difference between the air outside and water inside the radiator is high, and the heat is dissipated more quickly from water to the air. The air is generated with the help of a fan and also by the forward movement of the tractor.

Generally, the engine operates efficiently in the temperature range of 800C to 900C and it is always desired that the engine temperature should reach this temperature as early as possible in cool weather conditions and remain in this temperature range only under excessive hot weather conditions.

The thermostat is designed to maintain this temperature range by regulating the temperature of water/coolant circulating in the water jackets.

Types of Water Cooling Systems

There are two types of water-cooling systems.

• Thermosyphon
• Pump circulation system

Thermosyphon System

The pump is not fitted in this system. Circulation of water is done due to the difference in densities between hot and cold water.

However, in these cooling systems, the rate of cooling is low. Nowadays its usage is limited because we need to maintain the water to a certain level. It is simple in construction and cheap.

Working of Thermosyphon System

The thermosyphon cooling systems operate on the principle of natural convection. Thermosyphon water cooling system is based on the fact that water becomes light on heating and,

The top and bottom of the radiator are connected to the top and bottom of the cylinder water jacket respectively with the help of pipes. The radiator is cooled by causing air to flow over it. Airflow is achieved by vehicle motion or a fan provided.

The heated water inside the cylinder water jacket becomes light and moves out of the upper connection pipe into the radiator and travels down from the upper tank to the lower tank, rejecting heat as it travels.

This cooled water from the lower tank is passed into the cylinder water jacket and hence circulated again for the process.

The limitation of this system is that this cooling depends only on temperature and is independent of engine speed.

Pump Circulation System

In this cooling system, the circulation of water is done by providing a centrifugal pump. Due to this pump, the rate of flow of water is more. And the pump is driven by a belt from a crankshaft.

Here radiator may be fitted at any place convenient to the designer.

Working of Pump Circulation System

In this system, the direction of cooling water flow is upward from the cylinder head to the top tank of the radiator, then down through the radiator core to the bottom tank. From the bottom tank, it moves through the lower radiator hose to the cylinder block water jackets by the help of the water pump, which circulates the water.

Water enters the engine at the center of the inlet side of the pump. The circulating pump is driven by a belt from the crankshaft. As engine speed increases, the flow of coolant increases.

Advantages of Water-Cooling System

These are some advantages of a Water-Cooling System:

• In these types of cooling, we see a high heat transfer rate.
• This type of cooling system is used where the size or power of the engine is more.
• Thermal Conductivity is more
• Water is easily available
• Liquid has a high enthalpy of vaporization so the efficiency of water cooling is more.

Disadvantages of Water-Cooling System

The disadvantages of Water-Cooling Systems are mentioned below:

• Sometimes corrosion occurs inside the radiator or pipe or storage.
• Due to scaling heat transfer rate goes down after the long run, so it needs regular cleaning and maintenance.

Examples of Water-Cooled Engines:

All the modern engines (Cars, Bus, Trucks, etc.) nowadays use this type of cooling system.

FAQs.