COOLING SYSTEM: HOW-IT-WORKS (PART 1)

 

When engines work, they generate a lot of heat. This is due to the many controlled explosions going on in the engine cylinders.

To put this into perspective: A typical 4 cylinder vehicle cruising along the highway at around 50 miles per hour, will produce 4000 controlled explosions per minute inside the engine as the spark plugs ignite the fuel in each cylinder to propel the vehicle down the road. To know more about this, click here

Overheating occurs when this heat is not effectively removed from the system. Furthermore, if overheating is not controlled, it can destroy the engine in a matter of minutes.

An overheating car
An overheating car

In very extreme situations, there can be fire incidents which can burn up the whole vehicle.

A burning car
A burning car

The cooling system controls this heat and prevents your engine from overheating, thereby saving you a lot of money on repairs.

Today’s cooling system must maintain the engine at a constant temperature whether the outside air temperature is below 0 degrees celsius or as high as over 45 degrees celsius.

If the engine temperature is too low, fuel economy will suffer and emissions will rise.

Let’s Hit-The-Garage and find out How your engine stays cool.

The Cooling System.

First of all, we need to know the parts of the cooling system and what they do;

  • Water pump: This is the heart of the system. It pumps and circulates the coolant
A WATER PUMP
WATER PUMP
  • Thermostat: It controls the temperature of the coolant by enabling the coolant to either flow back into the radiator or to stay put in the engine.
THERMOSTAT
THERMOSTAT
  • The Radiator: Its function is to cool the coolant using the air flowing through the car’s grille.
A RADIATOR
A RADIATOR
  • Radiator cap: The cap controls the pressure in the system. Never open it when the engine is hot, it will release pressurized water at over 200 degrees celsius.
RADIATOR CAPS
RADIATOR CAPS
  • Passages; inside the engine blocks and heads
  • Cooling Fans: They suck in air at high pressure through the radiator from the front of the car. This air cools the coolant in the radiator.
RADIATOR COOLING FANS
RADIATOR COOLING FANS
  • Hoses: The hoses transfer the coolant from the engine to radiator and also to the car’s heater system.
HOSES AND TUBES
HOSES AND TUBES
  • Coolant temperature sensor; to control the opening and closing of the thermostat and also to start the cooling fan.
COOLANT TEMPERATURE SENSOR
COOLANT TEMPERATURE SENSOR
  • Coolant: The coolant that courses through the engine must be able to withstand temperatures well below zero without freezing.  It must also be able to handle engine temperatures in excess of 250 degrees without boiling.  The fluid must also contain rust inhibitors and a lubricant.
    The coolant used nowadays is a mixture of water and ethylene glycol (antifreeze). The recommended ratio is 50:50.
COOLANT
COOLANT

How does the engine stay cool?

The cooling system works by sending a liquid coolant through passages in the engine block and heads. 

Generally, as the coolant flows through these passages, it picks up heat from the engine. The heated fluid then makes its way through a rubber hose to the radiator in the front of the car. 

The hot coolant flows through the thin tubes in the radiator, and as a result, the air stream entering the engine compartment from the grille in front of the car cools it.

Afterwards, the cooled liquid returns to the engine to absorb more heat.  The water pump has the job of keeping the fluid moving through this system of plumbing and hidden passages.

A thermostat is placed between the engine and the radiator to ensure that the coolant stays above a certain preset temperature.

If the coolant temperature falls below this temperature, the thermostat blocks the coolant flow to the radiator. This forces the fluid instead through a bypass directly back to the engine.

The coolant will continue to circulate like this until it reaches the design temperature. At that point, the thermostat will open a valve and allow the coolant back through the radiator.

The radiator cap helps to relieve the system of pressure; high pressure is needed to boil water to temperatures of about 250 degrees celsius.

When the cooling system pressure reaches the point where the cap needs to release this excess pressure, a small amount of coolant is bled off. It could happen during stop and go traffic on an extremely hot day, or if the cooling system is malfunctioning.

When pressure is released under these conditions, the released coolant is captured and stored in a plastic tank that is usually not pressurized.

TO BE CONTINUED NEXT WEEK…

 

33 thoughts on “COOLING SYSTEM: HOW-IT-WORKS (PART 1)”

  1. I noticed that you used Water and coolant interchangeably. What is ‘supposed’ to go into the radiator? A special kind of Coolant or water (common coolant)? If it’s a special coolant:
    i. Should the pump be called “water pump”?
    ii. Why is it pressurised ‘water’ I have to worry about when I open the radiator cap?
    I’m asking because I’ve been informed that we’re exposing our cars to overheating when we use water.

    PS: Great content!

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