Engine Cooling System

The functions of the cooling system

• Bring the engine to normal operating temperature as quickly as possible
for achieving:
– Best performance
– Lower emissions
• Maintain proper engine operating temperature
• Provides a means of warming the passenger compartment
• To remove excess heat from the engine

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Cooling System Parts

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 Cooling System components

1- Water Jackets
• Surrounds the cylinders with water
passage.
• Absorbs heat from the cylinder wall.
• Pump move water to radiator where
heat is exchanged to the air.

2- Water pump
• Non-positive displacement pump which
circulates coolant around cooling system
(centrifugal pump).
• Simple impeller design.
• Usually driven by drive belt from
crankshaft by belt drive.

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 3- Radiator
 Transfers heat from coolant to the Tanks are on top and
atmosphere bottom.
 Two types – Vertical & cross flow
 Aluminum, brass, copper core; brass,
copper or plastic tanks
 Air movement through radiator created by
a mechanical fan or by vehicle movement Automatic
(ram air) dissipates heat transmission oil
coolers are at
Down flow type
 Coolant flows down through core tubes. bottom.
 Tanks are on top and bottom. Core tubes
 Coolant flows out of bottom tank back to engine
 Automatic transmission oil coolers are at bottom.
Tanks are on
sides.
Cross flow type
 Tanks are on sides.
 Allows lower hood line.
 Core tubes run horizontally
 Transmission oil cooler may be positioned Transmission oil
in side tank. cooler may be
positioned in side
tank.
 Radiator Cap

• The cap allows access to the cooling system for filling the coolant and
testing the radiator.
• The cap has two valves: a pressure relief valve set at around 1 bar
(gauge pressure) and a vacuum valve which is needed when the
engine cools down.
• Raises boiling point of fluid due to the high inside pressure.
• Able to take on more heat from the engine due to the raising of boiling
point
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 4- Coolant recovery tank
• Keeps the coolant level full in the system at all times.
• Works in conjunction with the radiator cap.
• When the engine heats up the coolant expands and flows to the recovery
tank.
• When the engine cooled the coolant contracts and creates a vacuum and
draws the fluid back into the radiator.
• Reduces air in system
• Reduces rust
• Less need to open radiator

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Coolant recovery tank

When engine is hot,

excess coolant
flows to expansion
tank reservoir.

When engine cools,

vacuum valve
opens to allow
coolant back to
radiator top tank.
5- Engine-Powered Fan
The main purpose is to generate air flow across radiator core tubes.

1- Mechanical Cooling Fan

It is driven by belt drive or fastened directly to the crank shaft

2- Electric Cooling Fan

The fan is driven by electric 12v DC motor.
The fan speed can be varied to achieve constant
coolant temperature during engine operation.

3- Belt Driven Cooling Fan Clutch

• Limits actual fan speed no more than 2000 rpm
• Engaged at low speeds
• Disengaged at high speeds
• Thermostatic (temp. sensitive)
 Fan Shroud

The fan shroud is fixed around the radiator from one side and has a
circular end around the fan from the other side.
• Causes the air to be channeled through the radiator. Making the
radiator more efficient.
• Also provides safety from the spinning fan blades.
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 Heater

• The hot water in the cooling system is used warm the passenger
compartment.
• A small radiator called a heater core is located in the dash area.
• Heater hoses direct the hot water to and from it.

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 Radiator Hoses & Heater Hoses

• The upper and lower radiator hoses

direct the fluid from the engine to the
radiator and back to the engine.
• Radiator hoses are used as
connections for the radiator, the heater
and bypass with the engine.
• Heater hoses are generic and come in
½”,5/8”, and ¾” diameter sizes.

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 Radiator Hoses & Heater Hoses
Flexible hoses carry coolant between radiator, engine block and heater core.

Upper hose from the

radiator is connected to
the cylinder head.

Hoses carry coolant to

passenger compartment heater.

Lower hose from radiator is connected

to water pump.

Expansion tank keeps system topped up.

Types of Hoses
Two types of radiator hoses:

 Molded (pre-formed),

 Flexible (universal).

Flexible type can be bent.

Support spring often fitted inside

flexible hose.
6-Thermostat
When the thermostat is cold the pass To top hose and
to the radiator is closed. radiator
Bypass allows coolant to circulate
around engine till the water
temperature reaches 80 C. Because
of hot water, the hot - wax-filled
pellet expands and opens thermostat.
Coolant allowed to flow to radiator
and by-pass port is blocked.

By-pass port

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Cross section through the thermostat

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 Coolant Temperature Sensor (CTS)
In smart engines (Computer controlled engines), the temperate level is
controlled by temperature sensors fixed in deferent locations in the
engine which feeds back signals to the computer and the computer
governs the pump and fan speed.
Sensors locations:
– Block
– Head
– Radiator tank

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7- The Coolant
• The coolant are mainly two types:
• Ethylene Glycol Based: (green water)
– Extended Life (Organic Acid Technology)
• Propylene Glycol Based: (red water)
– Environmentally Friendly (Low-Toxcity)
• Provides freeze and boil over protection:
• 50/50 mix with water:
– Most commonly recommended by automotive manufacturers
– Protects from about -36°C to + about 130°C
• 70/30 mix with water:
– Protects from about -54°C to about 136°C
• Provides protection from corrosion and achieves good heat transfer

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Cooling System Inspection
• Check belt tension.
• Check belt condition.
• Check belt hose condition.
• Blow out radiator fins.
• Check thermostat.
• Check radiator fan.
• Check water pump.

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