Handout Activity: HA1045

Transcription

1 Basic cooling system components HA Handout Activity: HA1045 Basic cooling system components The primary components in a vehicle cooling system are: radiator, thermostat & housing, water pump, cooling fan, radiator hoses and heater hoses. Cooling system components The primary components in a vehicle cooling system are: Radiator Thermostat & Housing Water Pump Cooling Fan Radiator Hoses Heater Hoses Radiator The radiator is located in a convenient position under the hood of the vehicle. Its actual location under the hood depends on the engine configuration, available space and the shape or line of the hood itself. The radiator consists of top and bottom tanks, and a core. The radiator core allows the coolant to pass through it in either a vertical down or horizontal cross flow direction. In addition, the radiator core serves as a good conductor of heat away from the engine Page 1

2 Basic cooling system components HA Cooling system header tank or reservoir The header tank, or reservoir, can be mounted separately from the radiator. It has a supply of coolant and is located higher than the top of the radiator. The reservoirs are usually made of hardened plastic, which allows for a visual checking of the fluid level through the plastic. Pressurized radiator cap On some tanks, a pressurized radiator cap may have been fitted. The pressurized radiator cap is used to increase the boiling point of the coolant. It can be located directly on the top of the radiator or on the header (or surge) tank Page 2

3 Basic cooling system components HA Thermostat & housing Cooling system thermostat and housing The thermostat is located under the thermostat housing. The thermostat regulates the flow of coolant, allowing a circulation of coolant to flow from the engine to the radiator when the engine is running at its operating temperature. But it is closed when the engine is cold to allow the engine to warm up more rapidly. The thermostat housing is normally located on the outlet side of the coolant flow from the engine. The majority of thermostat housings used today are made from an aluminum alloy, and will corrode away instead of the engine or cylinder head. This is known as a sacrificial component. Water pump Cooling system 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 Page

4 Basic cooling system components HA Cooling fan The cooling fan can be located on the water pump shaft, or it may be attached directly to the engine crankshaft. In most cases, this requires some engine power to drive the fan. The blades of the cooling fan can be made of steel or plastic. The blades draw cooling air through the radiator core, thus lowering the temperature of the coolant. Radiator hoses On most vehicles there are two radiator hoses. A top radiator hose is attached to the thermostat housing, which allows the heated coolant to enter the top or inlet side of the radiator. The bottom or lower radiator hose is connected between the outlet of the radiator and the inlet of the water pump. Radiator hose clamps The radiator hoses and by-pass hoses are held in position by clamps attached to the engine block or radiator assembly. These can be spring clamps, or wire wound clamps, or worm drive clamps Page 4

5 Basic cooling system components HA Heater hoses The heater hoses are normally pre-shaped for the particular make and model of vehicle you are servicing. The construction of the heater hose is the same as the radiator hose, with a reinforcing material embedded into it. The hot coolant comes in through the hose attached to the thermostat circuit, and as it sheds some of its heat into the vehicle, it cools down and returns to the engine via the water pump inlet. 1. The primary components in a vehicle cooling system are: Radiator Thermostat & Housing Radiator Cooling Fan Water Pump Heater Hoses 2. The majority of thermostat housings used today are made from an aluminum alloy, and will corrode away instead of the engine or cylinder head. This is known as a component. 3. The radiator consists of top and bottom tanks, and a. 4. The hot coolant comes in through the hose attached to the circuit, and as it sheds some of its heat into the vehicle, it cools down and returns to the engine via the water pump inlet. 5. The cooling fan can be located on the water pump shaft, or it may be attached directly to the engine. Score / Page 5

6 Radiator Handout Activity: HA227 HA227-2 Radiator Many radiators are mounted at the front of the vehicle in the path of greatest airflow. The air carries heat away, cooling the liquid before it returns to absorb more heat from the engine. Many radiators are mounted at the front of the vehicle in the path of greatest airflow. The air carries heat away, cooling the liquid before it returns to absorb more heat from the engine. Where a radiator is mounted also depends on space - how the engine is mounted. A header tank can be mounted away from the radiator, where it provides a coolant supply, stored above the engine. It can be made of sheet metal, or hardened plastic. The radiator has 2 tanks and a core. The materials used in the radiator must be good heat conductors like brass or copper. Brass and copper are often used for tanks, combined with a copper core. Modern vehicles often use plastic tanks combined with an aluminium core. This saves weight but still provides good heat transfer. The core consists of a number of tubes that carry coolant between the 2 tanks. The tubes can be in a vertical downflow pattern, or a horizontal crossflow pattern. A crossflow radiator fits more easily under a steeply sloped bonnet. In the core, small, thin, cooling fins are in contact with the tubes. The shape of the fins increases the surface area exposed to the air. Where coolant touches tube walls, and where the tubes touch the fins, heat is removed from the coolant by conduction, then by radiation and convection at the surface of the fins. Air rushing by carries the heat away. Liquid emerges cooler at the bottom of the radiator. It travels through the lower radiator hose to the water pump inlet, then through the engine again.

7 Radiator HA A tank can be mounted away from the radiator, where it provides a coolant supply, stored above the engine. 2. In the core, small, thin, cooling fins are in contact with the tubes. The shape of the fins increases the area exposed to the air. 3. The tubes can be in a horizontal pattern. 4. Liquid emerges cooler at the bottom of the radiator. It travels through the lower radiator hose to the pump inlet, then through the engine again. 5. The tubes can be in a vertical pattern. Score / Page 2

8 Coolant hoses Handout Activity: HA228 HA228-2 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. 1. Heater hoses carry a volume. 2. Most hoses are made of, and since they are subject to pressure, they are reinforced with a layer of fabric. 3. Coolant is transferred throughout the cooling system by. Score / 3

9 Water pump Handout Activity: HA229 HA229-2 Water pump The water pump pumps coolant through the engine and radiator. It is belt-driven from a pulley. A hose connects it to the bottom of the radiator. The water pump is usually in front of the cylinder block, beltdriven from a pulley, on the front of the crankshaft. A hose connects it to the bottom of the radiator where the cooler liquid emerges. It has fan-like blades on a rotor or impeller. Coolant enters the center of the pump. The rotor spins, and centrifugal force moves the liquid outward. It is driven through the outlet into the cooling passages called waterjackets. Waterjackets are passages in the engine block and cylinder head that surround the cylinders, valves and ports. Coolant can be also directed to hot spots such as the exhaust ports in the cylinder head, to stop local overheating. 1. are passages in the engine block and cylinder head that surround the cylinders, valves and ports. 2. It has fan-like blades on a rotor or. 3. The water pump is usually in front of the cylinder block, belt-driven from a pulley, on the front of the. Score / 3

10 Cooling system thermostat Handout Activity: HA230 HA230-2 Cooling system thermostat A thermostat shortens an engine s warming-up period. It is a valve operated by coolant temperature. It stops coolant circulating through the system while the engine is cold. The thermostat helps an engine to warm up. It s found in different positions on different engines. It is a valve that operates according to coolant temperature. When coolant is cold, a spring holds the valve 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 in the engine gets hotter and hotter. This thermostat has a wax-like substance that expands as the engine nears its operating temperature. This starts to open the valve. Coolant starts to flow to the radiator. Thermostats have a small hole or valve to let out air that was trapped in the engine block. Heated coolant is pumped from an outlet in the cylinder head. It goes into the upper radiator hose, then to the radiator. 1. When coolant is cold, a holds the valve closed. 2. Thermostats have a small hole or valve to let out air that was trapped in the engine. 3. It is a that operates according to coolant temperature. Score / 3

11 Cooling fan Handout Activity: HA231 HA231-2 Cooling fan A fan helps generate airflow through a radiator. It can be driven either by a belt off the crankshaft, or electrically. It can be controlled according to temperature. 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 heatsensitive 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.

12 Cooling fan HA Fan blades can be rigid or. 2. More and more modern vehicles now use an fan. 3. A heat-sensitive switch in contact with the coolant can work like a, and turn the fan on and off according to coolant temperature. 4. 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. 5. When an engine is mounted longitudinally, its fan is usually mounted on the shaft. Score / Page 2

13 Temperature indicators Handout Activity: HA232 HA232-2 Temperature indicators A temperature indicator is a device that is sensitive to engine temperature. It sends readings to a temperature gauge or a warning lamp. Overheating can seriously damage an engine, so having warning of trouble is obviously useful. A device that s sensitive to engine temperature sends readings to a temperature gauge or a warning lamp. To give an accurate reading this sensor must always be immersed in liquid. Indicators that measure coolant levels can give warning if the level falls too low. 1. To give an accurate reading this sensor must always be immersed in. 2. A device that s sensitive to engine temperature sends readings to a gauge or a warning lamp. Score / 2

14 Radiator pressure cap Handout Activity: HA233 HA233-2 Radiator pressure cap One way to help prevent a coolant boiling is to use a radiator pressure cap that uses pressure to change the temperature at which water boils. If a coolant boils, it can be as serious for an engine as having it freeze. Boiling coolant in the waterjacket becomes a vapor. No liquid is left in contact with the cylinder walls or head. Heat transfer by conduction stops. Heat builds up, And that can cause serious damage. One way to prevent this is with a radiator-pressure cap that uses pressure to change the temperature at which water boils. As coolant temperature rises, the coolant expands and pressure in the radiator rises, and that lifts the boiling point of the water. Engine temperature keeps rising, and the coolant expands further. Pressure builds against a spring-loaded valve in the radiator cap until at a preset pressure, the valve opens. In a recovery system, the hot coolant flows out into an overflow container. As the engine cools, coolant contracts and pressure in the radiator drops. Atmospheric pressure in the overflow container then opens a second valve, a vacuum vent valve, and overflow coolant flows back into the radiator. This system stops low pressure developing in the radiator, and that stops atmospheric pressure collapsing the radiator hoses. 1. Pressure builds against a spring-loaded in the radiator cap until at a preset pressure, the valve opens. 2. One way to prevent this is with a radiator-pressure cap that uses pressure to change the at which water boils. 3. Atmospheric pressure in the overflow container then opens a second valve, a vacuum vent valve, and overflow coolant flows back into the. 4. Boiling coolant in the waterjacket becomes a. Score / 4

15 Recovery system Handout Activity: HA234 HA234-2 Recovery system A recovery system keeps the cooling system full. As engine temperature rises, coolant expands and flows out into a container. As it cools it returns to the radiator. A recovery system maintains coolant in the system at all times. As engine temperature rises, coolant expands. Pressure builds against a valve in the radiator cap until, at a preset pressure, the valve opens. Hot coolant flows out into an overflow container. As the engine cools, coolant contracts and pressure in the radiator drops. Atmospheric pressure in the overflow container opens a second valve, and overflow coolant flows back into the radiator. No coolant is lost and excess air is kept out of the system. Like water, air contains oxygen which reacts with metals to form corrosion. 1. As the engine cools, coolant and pressure in the radiator drops. 2. Atmospheric pressure in the overflow container opens a second, and overflow coolant flows back into the radiator. 3. As engine temperature rises, coolant. Score / 3

16 Boiling point & pressure Handout Activity: HA235 HA235-2 Boiling point & pressure Changes in water pressure can change the temperature at which it boils Water at atmospheric pressure at sea level boils at 100 degrees Celsius or 212 degrees Fahrneheit. That is it s boiling point. If the water is put under pressure, higher than atmospheric pressure, it boils at a higher temperature. If the pressure is decreased below sea level atmospheric pressure, it boils at a lower temperature. Therefore, raising pressure above atmospheric pressure increases the boiling point. Lowering it below atmospheric pressure lowers the boiling point. Changing water pressure changes the temperature at which it boils. 1. If the water is put under pressure, higher than atmospheric pressure, it boils at a temperature. 2. Changing water pressure changes the at which it boils. Score / 2

17 Electrolysis Handout Activity: HA236 HA236-2 Electrolysis Electrolysis is a chemical and electrical process. It occurs when two different metals are in contact, in the presence of a moist agent such as water. One of the metals is corroded away. Electrolysis is the process of causing a chemical change in a compound by passing a direct electrical current through it. For example, electrolysis of water separates the water molecules into oxygen and hydrogen. There are many positive uses for electrolysis, particularly in the manufacture of chemicals, such as gases and metals, and other materials. Electrolytic processes can also have undesirable effects. For instance, in automotive cooling systems, if its effect is not counteracted, electrolysis can quickly cause damaging corrosion when two different metals are in contact with each other in the presence of a liquid, such as engine coolant. A wet cell battery, such as a typical lead/acid car battery, works as a result of the reverse of the electrolysis process. In this case, metal plates are submerged in liquid acid, and the resulting chemical reaction creates an electron flow between the two plates. 1. In the case of a wet cell battery, metal plates are submerged in liquid, and the resulting chemical reaction creates an electron flow between the two plates. 2. Electrolysis is the process of causing a change in a compound by passing a direct electrical current through it. 3. In automotive cooling systems, electrolysis can quickly cause damaging when two different metals are in contact with each other in the presence of a liquid, such as engine coolant. 4. Electrolysis of water separates the water molecules into oxygen and. Score / Page 1

18 Centrifugal force Handout Activity: HA237 HA237-2 Centrifugal force Centrifugal force is a force pulling outward on a rotating body. Centrifugal force is a force pulling outward on a rotating body. A vehicle turning a curve is a similar system to this rotating body, so it is subject to centrifugal force too. Centrifugal force resists turning, and tries to keep the vehicle moving in a straight line. Centrifugal force is also the force that causes an out-of-balance wheel to vibrate. Centrifugal force can also be useful. When coolant enters the center of this pump, and the rotor spins, centrifugal force moves the liquid outward. 1. Centrifugal force turning, and tries to keep the vehicle moving in a straight line. 2. Centrifugal force is a force pulling on a rotating body. Score / 2

19 Thermo-switch Handout Activity: HA238 HA238-2 Thermo-switch A thermo-switch opens and closes according to pre-set temperature levels. A thermo-switch opens and closes according to pre-set temperature levels. Some are mechanical, others are electrical. It may be designed to switch off when temperature rises above a certain level, or it can be made to switch on, when the temperature reaches a certain level. Heat switches can operate on the bimetallic strip principle. It consists of two different metals or alloys attached backto-back. As different metals and alloys heat and cool, they expand, and contract, differently. That means that if they are joined, and then heated, the faster expansion of one will force the whole strip into a curved shape. As the strip changes shape, it can be designed to complete a circuit, and a resulting electrical signal can then do a range of tasks, or it might have a mechanical effect, simply opening a passageway. Cooling then produces the opposite effect. Breaking the circuit, and closing the passage. 1. Some are mechanical, others are. 2. As the strip changes shape, it can be designed to complete a, and a resulting electrical signal can then do a range of tasks, or it might have a mechanical effect, simply opening a passageway. 3. A thermo-switch opens and closes according to pre-set levels. 4. switches can operate on the bimetallic strip principle. Score / 4