Page 178 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

b Honeycomb type radiator core: It is also known as cellular type core. In this type of core, air flows across
the tubes and water remains on the outside. This core is made up of many air cells. Radiators are usually
made of copper or brass, because these Metals have the property of cooling quickly. All its joints are joined by
soldering, so that they can be easily opened by heating for repair. This type of radiator core looks as if it is a
beehive, hence it is called also called ‘honeycomb’.

Thermostat: A thermostat is a device that opens automatically at a predetermined temperature. It is installed
in the water pipe going from the engine to the radiator. As shown in the figure, when the engine is cold, the
thermostat closes and the water pump normally pumps water around the cylinder block. When the engine reaches
the correct temperature, the thermostat opens and water is circulated through the radiator to cool the engine.
Types of Thermostat
There are two types of thermostat

i Bellow type thermostat
ii Wax pellet thermostat
1 Bellow Type Thermostat: consists of a flexible metal bag, both the ends of which are closed. This metal
bag is filled with ethyl with low boiling point temperature. When the engine is cold, the valve closes its outlet
passage and does not allow water from the engine to reach the top tank of the radiator. But water circulates
through the bypass port of the engine.

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CITS : Automotive - Mechanic Diesel - Lesson 47 - 56 CITS : Automotive - Mechanic Diesel - Lesson 47 - 56