Engines - Cooling Systems and Air Conditioning Flashcards
Name a component used to improve outside air cooling
Cooling fins
Give 2 advantages of air cooling
Less engine maintenance
Shorter warm-up period
Where does the air come from in outside air cooling?
Where does the air come from in forced air cooling?
Air from outside the car enters to cooling system when the car is moving
Air is blown in by a fan, which still produces airflow when the car is stationary
Where is the oil cooler mounted?
What is its purpose?
Mounted completely in the outside air flow
To cool the oil so that it does not lose its lubricating properties
By how many degrees is oil cooled by outside air flow?
25 to 50 degrees C
Which kinds of cooling are direct and which are indirect:
Outside air cooling
Forced air cooling
Oil cooling
Liquid cooling
Direct
Direct
Indirect
Indirect
List 3 advantages of liquid cooling
Engine cools more uniformly
Less engine noise
Engine remains at temperature for longer, so that it can get started more quickly after a pause in driving
List the main 5 components of a liquid cooling system
Coolant pump
Thermostat
Fan
Radiator
Pressure cap
What is the function of a thermostat in a liquid cooling system
Controls the flow of coolant through the radiator
What is the purpose of the pressure cap in a liquid cooling system?
To increase the pressure and therefore increase the boiling point of the coolant
What will dashboard signals inform you about in terms of the coolant?
Coolant temperature
Coolant level
What is a thermostat referred to as if it only operates on one valve? What about if it operates on two?
A single-action thermostat
A double-action thermostat
How does a thermostat operate?
Wax, which expands as it heats up
Where is the pressure cap usually located? What does it do?
On the expansion tank or the radiator
Raises the boiling point of coolant
What should you never do with a pressure cap? Why?
Take it off while still hot
The water can boil immediately and shoot into your face
What 2 valves can be found inside a pressure cap?
Vacuum valve
Relief valve
What do you use an anti-freeze gauge for? How to you use one? (in 4 steps)
Determine the freezing point
Open the glass gauge cover
Drop a tiny bit of coolant onto the plate under the over
Press the cover back down
Put it to your eye and look at the reading
In coolant freezes, what components can it cause to crack?
Engine block
Cylinder head
Radiator
Coolant hoses
What is the optimum temperature for an engine called?
Operating temperature
The engine dissipates its heat through the cylinder wall. Where does this heat go?
The coolant
How does the heated coolant transfer its heat to the outside air?
Via the radiator
List 3 symptoms of insufficient coolant
Overheated engine
Uncontrolled combustion
Poor lubrication
List 3 symptoms of excessive coolant
High fuel consumption
Internal engine contamination
Condensation of fuel droplets
List 2 functions of the expansion tank
Provide coolant when there is a shortage
Store excess coolant
Can the expansion tank be connected to the cooling system by systems where the coolant does flow through the expansion tank or systems where it doesn’t flow through the expansion tank?
Both
What 2 things happen in a cold expansion tank when the temperature rises? What will happen when it lowers back down (other than the reverse of when it goes up)?
The excess pressure valve on the pressure cap opens
The coolant flows into the expansion tank
The vacuum valve on the pressure cap opens
What is a cooling system referred to as if the coolant does not flow through the expansion tank?
What about when it does?
Cooling system with a cold expansion tank
Cooling system with a hot expansion tank
What is the main feature of a cold expansion tank that is different to hot, in terms of process
The pressure cap always remains closed
Where is a hot expansion tank positioned? Why?
Above the radiator
So that the radiator is always full of coolant
What is the purpose of a radiator?
To dissipate heat from the coolant to the outside air
What is the radiator core usually made of?
What about the water tanks?
Aluminium
Plastic
What are the main 2 components of the radiator core mesh?
Small pipes
Cooling fins
Why do radiator cores have cooling fins?
To increase the cooling surface area
Name the 2 main types of radiator
Crossflow
Downflow
Other than the water flowing down, list 2 ways to know if a radiator is downflow
The water tanks are on the top and bottom
There is a filler cap
Other than the water flowing from right to left or lefft to right, list 2 ways to know if a radiator is crossflow
The water tanks are on the left and right
The filler cap is on the expansion tank, no the radiator
Why are crossflow radiators used more in modern cars?
Smaller height
What is the main difference between an electric thermostat and a mechanical one?
The electric thermostat has a filament in the wax
Give one advantage of using an electric thermostat over a mechanical one
Can respond more effectively to different operating situations
What happens to refrigerant when it flows through the evaporator?
It turns from liquid to gas
What happens to refrigerant when it flows through the evaporator and the outside temperature is very low? (3 things)
Not all of it turns to gas
A little liquid refrigerant leaves the evaporator
The compressor is fed with liquid refrigerant
What happens to refrigerant when it flows through the evaporator and the outside temperature is very high?
A little liquid refrigerant leaves the evaporator
What happens if a little liquid refrigerant leaves the evaporator and is therefore fed to the compressor?
The compressor is damaged, because it cannot compress a liquid
What does the accumulator do?
Collects the unevaporated liquid refrigerant that otherwise would flow to the compressor and damage it
What kind of orifice always lets through the same amount of refrigerant?
Fixed orifice
What can be used instead of a fixed orifice, which reduces the chance of liquid getting to the compressor?
An expansion valve
Where in the system would the accumulator be put in comparison to the fixed orifice?
What about the filter dryer in comparison to the expansion valve?
After
Before
List 2 components which are specific to a non-regulated air conditioning system
Accumulator
Fixed orifice
List 2 components which are specific to a controlled air conditioning system
Filter dryer
Expansion valve
Where is the condenser located? Why?
In the front centre of the engine compartment
To maximise airflow through it
Where are the evaporator and expansion valve located?
In the back of the engine compartment, behind the bulkhead
What is the bulkhead?
The panel that separates the engine compartment from the passenger compartment of a vehicle
How does an internal combustion engine drive the air conditioning?
Using a belt
List the 4 main components of the air conditioning system
The evaporator
The valve (can be an expansion valve or fixed orifice)
The compressor
The condenser
Which of the 4 main component of the air conditioning system does the refrigerant flow through?
All of them
What 2 things happen to the refrigerant when the temperature drops?
The pressure of the refrigerant remains the same
The temperature of the refrigerant drops
In what state is the refrigerant when it leaves the condenser?
Liquid
