By Bradley F.N. Robinson

Heat is a natural byproduct of burning fuel, and due to the heat created by the internal combustion engine it is important that an efficient form of cooling system is in place. This will ensure

the best power and fue; economy is achieved, as well as preventing damage to the engine components by overheating. The cooling system is designed to keep the engine operating at

a given temperature and prevents the engine from seizing.

In this assignment you will find research on:

The types of cooling systems of the internal combustion engine.

The components that make up the cooling system. The function of these components. Information about servicing the cooling systems. The safety issues concerning the cooling system and

components.

Contence:

Page 1: Ttle page

Page 2: Introduction & contense

Page 3 - 4: The liquid cooling system

Page 4 – 8: Cooling system components

Page 9 – 10: The air cooling system

Page 10 – 12: AntiFreeze/Coolant & Safety

Page 13 – 14: References

Liquid cooling system

A liquid cooling system uses coolant to remove excess heat from an engine. It also uses a heat-sensitive valve to control circulation to help an engine heat up and maintain its operating temperature. The cooling system of a water-cooled engine consists of: the engine's water jacket, a thermostat, a water pump, a radiator and radiator cap, a cooling fan (electric or belt-driven), hoses, the heater core, and usually an expansion (overflow) tank.

In this liquid-cooling system, a coolant is stored in a radiator, and in the engine.

A water pump forces coolant from the radiator, through the bottom hose, through passages called waterjackets in the engine block (see cooling jackets in above diagram). It collects

heat by conduction, and becomes hot itself. Heated coolant then returns to the radiator for cooling.

And the cycle is repeated. Heat is removed from the engine, and dispersed. Preventing overheating is one function of the cooling system. It also helps the engine reach its best operating temperature as soon as possible. Every engine has a temperature at which it operates best. Below this temperature, ignition and combustion can be difficult.

Cooling system Components

- Cooling fans

In a vehicle moving at high speed, airflow through the radiator cools the coolant, but at low speed or when the engine is idling, extra airflow comes from a fan.

Fans can be driven in different ways. More and more modern vehicles now use an electric fan. Air-conditioned cars often have extra fans. Electric fans can be behind the radiator, in front, or both. This arrangement would be difficult with a belt-driven fan. Some fans can be driven from the crankshaft.

When an engine is mounted longitudinally, its fan is usually mounted on the water pump shaft. The drive belt then turns the water pump and fan. Some use a hydraulic link from the power steering system. Fan blades can be rigid or flexible. Rigid blades tend to be noisy and use more energy. This noise can be reduced by using irregular spacing of the fan blades.

Some vehicles use a shroud to direct all of the air that the fan moves, through the radiator core. At high speeds, plenty of air is already flowing through the radiator. If the fan is always working at full speed, it’s a waste of energy. And since the engine drives the fan, it’s a waste of fuel too. What’s needed is some way to control the fan. A heat-sensitive switch in contact with the coolant can work like a thermostat, and turn the fan on and off according to coolant temperature.

Another way to alter the speed of the fan is with a viscous hub. This type of fan slips when it is cold, but as the engine heats up, it grips more and more.

- Radiator

The radiator is a device designed to dissipate the heat which the coolant has absorbed from the engine. It is constructed to hold a large amount of water in tubes or passages which provide a large area in contact with the atmosphere. It usually consists of a radiator core, with its water-carrying tubes and large cooling area, which are connected to a receiving tank (end cap) at the top and to a dispensing tank at the bottom. Side flow radiators have their "endcaps" on the sides, which allows a lower hood line (getting more common in modern vehicles).

In operation, water is pumped from the engine to the top (receiving) tank, where it spreads over the tops of the tubes. As the water passes down through the tubes, it loses its heat to the airstream which passes around the outside of the tubes. To help spread the heated water over the top of all the tubes, a baffle plate is often placed in the upper tank, directly under the inlet hose from the engine.

- Radiator cap

The radiator cap acts as more than just a "lid" for your radiator; it keeps your engine cool by sealing and pressurizing the coolant inside it.

What makes the radiator cap special is that it is designed to hold the coolant in your radiator under a predetermined amount of pressure. If the coolant was not kept under pressure, it would start to boil, and soon you would have boiled all of your coolant away.

The radiator filler neck has an overflow tube right between the two sealing surfaces. If the pressure in the cooling system exceeds the preset rating of your cap, its pressure relief valve allows the lower seal to be lifted from its seat. Then the excess pressure (coolant,air) can squish through the overflow tube to the ground or the coolant reservoir.Once enough pressure has been released (the caps preset rating), the pressure relief valve is again closed by the spring.

- Expansion (overflow) tank

Several cooling systems make use of a clear plastic container, which is connected to the overflow tube from the radiator. This container provides extra storage space for the coolant when it expands and is called the expansion, or overflow tank. It is also known as the coolant reservoir, or overflow canister.

As the engine heats up, the coolant inside it expands. Without the expansion tank, the coolant would flow out of the overflow tube and be lost from the cooling system onto the street. Instead, the coolant flows into the expansion tank.

Since a vacuum is created in the cooling system when the engine cools, the vacuum causes some of the coolant in the expansion tube to be sucked back into the system. Because a cooling system with an expansion tank is virtually a closed system, the coolant can flow between the system and the expansion tank as it expands and contracts. This way, no coolant is lost if the system is functioning properly.Another function of the expansion tank is to remove air bubbles from the cooling system. Coolant without air-bubbles is much more efficient than coolant with air bubbles, because it absorbs heat much faster.

- Radiator & coolant hoses

Cooling system hoses are flexible to allow for movement, and molded to fit the shape needed. Most hoses are made of rubber, and reinforced with a layer of fabric.

Coolant is transferred throughout the cooling system by hoses.

Most vehicles have the engine mounted on flexible mountings to reduce noise and vibration. Since the radiator is mounted to the vehicle body, flexible hoses are needed. Coolant is also carried to the heating system which is usually inside the cabin of the vehicle.

Coolant hoses vary in diameter depending on the volume of coolant that passes through them. Heater hoses carry a smaller volume.

Most hoses are made of rubber, and since they are subject to pressure, they are reinforced with a layer of fabric. They are

moulded to a special shape to suit the model and make of vehicle. Some heater coolant hoses also have special shapes. All hoses are subject to hot coolant and high under-bonnet temperatures, and they can deteriorate and fail.

- Thermostat

There is a thermostat in place to shorten the warming-up period. It operates according to coolant temperature. When coolant is cold, it is closed. When a cold engine starts, coolant circulates within the engine block and cylinder head and through a coolant bypass to the water pump inlet. It can’t get to the radiator. As the engine warms up, the coolant trapped in the engine gets hotter and hotter. This starts to open the thermostat, allowing hot coolant to flow to the radiator.

- Water pump

The water pump is normally bolted to the front of the engine block. The bottom radiator hose comes from the radiator and is connected to the water pump inlet.

The water pump is driven by the engine via a fan or drive belt.

As the coolant leaves the outlet of the radiator, which has removed much of its heat, the water pump forces it through the water jackets by the action of the impeller in the pump.

Air cooled cooling system

Air cooling is a method of dissipating heat. It works by making the object to be cooled have a larger surface area or/and have an increased flow of air over its surface. An example of larger surface area is to add 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 increased air flow, it is done by using a fan blowing air into or onto the object one wants to cool. In many cases the addition of fins adds to the total surface area making a heatsink that makes for greater efficiency in cooling.

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).

Air-cooling is common on smaller internal combustion engines. They may be small but they still generate a lot of heat. It’s the air that does the work of keeping them cool, so an air-cooling system is usually simple. That’s useful on an engine where weight is important. And it works best on the engine that’s exposed to a high airflow. Almost all motorcycles used to be air-cooled but modern motorcycles are larger and more complex, and some are now liquid-cooled.

Some engines use what are called cooling fins. Their design makes the exposed surface area as large as possible, which allows more heat energy to radiate away, and be carried off in convection currents in the air. More air flows over the fins and more heat is carried away. For a vehicle moving at speed, airflow over the engine is high. At low speeds or during idling, heat builds up. Then the engine can use some help. Air should always be able to flow over the engine effectively. One way to remove heat is to use a fan, with shrouds and ducts to direct air to the cylinders.

There are many places to mount a fan and many ways to drive it. For instance, in some engines it’s on the flywheel, driven by fan-belts off the crankshaft.

Antifreeze/Coolant

Coolant prevents an engine from overheating in use and from freezing when idle.

The amount of heat generated by an engine is the equivalent of that required to heat a large house in winter in very cold climates. As engines and vehicles become smaller and more powerful they generate even more heat in a confined space, and aerodynamically efficient body designs tend to direct air away from, rather than into, the engine bay.

When an engine stands idle in cold weather, water in the cooling system will expand as it freezes, and this can have sufficient force to crack the engine block or radiator.

An effective coolant must therefore contain good heat transfer properties, have a higher boiling point and lower freezing point than water, prevent corrosion and erosion, resist foaming, be compatible with cooling system component materials, be compatible with hard water, resist sedimentation, and be as chemically stable as possible.

A concentrate, usually made of Ethylene Glycol together with some protective additives, is mixed with water to produce coolant. Propylene Glycol, which is non-toxic, is sometimes used in the mixture, as well as, or even instead of, the more toxic Ethylene Glycol. Glycol does not absorb heat as effectively as water, but when added to water it has the ability to lower the fluid’s freezing point as well as raise its boiling point.

A common Glycol to water ratio used is 50:50. This will lower the freezing point of the fluid to minus 39°C and raise the boiling point to 108°C. Manufacturers can recommend other specific mixture ratios, but below 33% Glycol the coolant will give inadequate freeze protection, and above 65% Glycol the mixture has inadequate heat absorption.

A fully formulated coolant is comprised of a careful balance of ethylene or propylene glycol with rust inhibitors, corrosion inhibitors, scale inhibitors, pH buffers for the acid to alkali balance, anti foaming agents, and reserve alkalinity additives.

Coolant should be changed at recommended intervals, because some of the additives will age and deteriorate over time, reducing the effectiveness of the coolant. While some coolants are compatible with others, changing the chemical balance in the cooling system can affect coolant performance, so mixing different types of coolant is not recommended.

Safety precautions

PRECAUTIONS MUST BE TAKEN WHEN DEALING WITH THE RADIATOR OR SERIOUS BURNS CAN RESULT.

Here are a few pointers for dealing with an overheated radiator:

Turn off the A/C. If the car is not seriously overheating, this will reduce the engine's temperature. The AC evaporator is located in front of the radiator, and it adds heat to the air going to your engine. The hotter the incoming air is, the less efficient the radiator will be.

Turn on your heater (set on highest temperature setting, with blower on highest setting). This will be uncomfortable

for you, but it will cool the engine by transferring the heat to the air. Roll down the windows, and remember how 'hot' you'll get if your engine needs replacement!

If you're stuck in traffic, pull over and stop. Unless you're moving, very little cool air reaches the radiator. Open the hood and let the engine cool off. This takes time, so be patient. Use the time to go get a jug of water or antifreeze.

Check the overflow tank coolant level. If it's empty, the radiator is probably low on coolant.

Check the pressure of the system by wrapping a cloth around the upper radiator hose and squeezing it. If it's still under pressure (hot) it will not squeeze easily. Wait until it does.

Place a large cloth over the radiator cap, and CAREFULLY release the pressure.

DANGER: SERIOUS BURNS CAN RESULT FROM THE HOT COOLANT. IF IN DOUBT, WAIT UNTIL THE ENGINE COOLS

COMPLETELY.

If the coolant is low, start the engine, and slowly add the water or coolant necessary to fill it up. THE ENGINE MUST BE RUNNING. ADDING COOLANT TO A WARM ENGINE CAN CRACK THE BLOCK. By running the engine, the coolant keeps moving and reduces the chances of this type of damage occurring.

Ethylene glycol antifreeze has a sweet taste that can contribute to its accidental ingestion or its deliberate use as a murder weapon, as attributed by the many sensational media reports concerning it. Symptoms of antifreeze poisoning include severe diarrhea and vomiting; usually farther into the intoxication, signs of delirium, paranoia and intense hallucinations manifest. Antifreeze poisoning can be identified from the growth of calcium oxalate crystals in the kidneys. An embittering agent such as denatonium can be added to ethylene glycol to help discourage either accidental or deliberate poisoning.

Ethylene glycol is toxic to many animals, including cats and dogs, so waste antifreeze should be disposed properly or recycled. In some places, it is permitted to pour moderate amounts down the toilet, but there are also places where it can be taken for processing.

References

Sami Garage WebPage:

http://www.samigarage.com/images/suzuki_cooling_system.jpg

Google images

Wkikpedia (online incyclopedia)

http://en.wikipedia.org/wiki/Air_cooling

http://en.wikipedia.org/wiki/Water_cooling

http://en.wikipedia.org/wiki/Antifreeze

CDXGlobal (online automotive resource)

http://www.cdxetextbook.com/engines

ATV Mad Blog (motorcycle web sight)

http://out2win.com/catalog/images/Sudam125.jpg

Muscle car club. Com (online muscle car web sight)

http://www.musclecarclub.com/library/tech/cooling.shtml

Samarians.com (Automotive illustrated glossary)

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Automotive Mechanics Vol. 1, 8th edition (Automotive mechanics textbook) – By Ed May & Lez Simpson

2CarPros.com (online automotive questions and answers)

http://www.2carpros.com/first_things/images/engine_therrmostat.jpg

Nengun Performance ( performance car web sight)

http://image.nengun.com/catalogue/original/nengun-1564-00-arc-radiator_cap.jpg

AutoZone - Pro Care (Automotive reference library)

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jagsthatrun.com (radiator hose specialists websight)

http://www.jagsthatrun.com/Pages/images/Hose-Splicing-Kit.jpg