Automobile Engineering in ME
The condition that causes vapour locking in a brake system is

Overcooling of the brakes during high speed driving
Keeping the vehicle without use for an extended period
Overheating of the fluid due to frequent brake application
An excessively high engine speed on a downhill road

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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
Cushion ring which prevents piston slap and knock
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

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