Page 71 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Reasons for frequently occurring abnormal wear in cylinder

head components and its Effects on engine performance

Objectives: At the end of this lesson you shall be able to
• demonstrate Reasons for frequently occurring abnormal wear in cylinder head components
• effects on engine performance due to abnormal wear.

Cylinder head defects, causes and solutions Faults, Causes and Remedies of Cylinder Head
i Overheating of the engine: The main reason for overheating of the engine is accumulation of excessive
amount of carbon in the combustion chamber.
To protect the engine from overheating, the cylinder head should be de-carburized
ii The face of the cylinder head becomes crooked: The main reason for this defect is that the nuts and bolts
of the cylinder head are not tightened properly.

To prevent the face of the cylinder head from getting crooked, the nuts and bolts should be tightened opposite to
each other while tightening the cylinder head.
Overhauling of Cylinder Head

While overhauling the cylinder head, the carbon of the combustion engine should be properly cleaned. Additionally,
when water is poured into a hot engine, the cylinder head may crack. Therefore, it is necessary that all the water
passages in the cylinder should be sealed and then the cracks should be checked by creating water pressure in it.

While cutting the valve seat, carbon should be cleaned from the seat surface. Apart from this, while fitting the
valve guide, it should be cleaned properly. If the valve guide is loose, a new valve guide should be used.
The surface of the cylinder head should be flat. To check the surface of the cylinder head, its straightness and
flatness should be checked with a straight foot rule and a feeler gauge as shown in the picture. This should be
checked at least at 6 places. The feeler gauge of 0.05 mm should not go between the foot rule and the head. If
the feeler gauge goes between the foot rule and the head, then grinding of the cylinder head should be done. (iii)
Cracking of cylinder head. There are following reasons for crack in the cylinder head.

a Sudden falling of the cylinder head.
b Adding cold water when the engine is hot.

Prevention Cold water should not be added when the engine is hot. If due to some reason a crack appears in the
cylinder head, then after welding the cylinder head, the face grinding should be done.

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CITS : Automotive - Mechanic Diesel - Lesson 11 - 14