Automobile Engineering in ME
The function of a second ring is that it is a

Back up oil control ring which will work in place of the bottom ring when it is broken
Compression ring and aids the top ring in sealing and cooling
Back up compression ring which will work in place of the top ring when it is broken
Cushion ring which prevents piston slap and knock

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Automobile Engineering in ME
The function of a radiator fan in the cooling system is that

It is turned by wind force as the vehicle moves forward, and its rotation drives the water pump
It blows air through the radiator when necessary
It cools the engine by blowing air onto the cylinder block
It draws heat out of the engine compartment

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