What are the causes of cylinder head cracking?

Causes of cracked cylinder head:

1. Scale deposits
2. Inefficient cooling water
3. Uneven tightening of bolts and fuel valves
4. Corrosion at the combustion surface of the cylinder head.
5. Fluctuating cooling water temperature (excessive temperature gradient)
6. Overloading of engine
7. Faulty relief valve
8. Mechanical failure due to gas corrosion, acidic corrosion due to leaky exhaust valves
9. Water side corrosion
10. Defect in cylinder head casting
11. Inflexible structure under firing

Indications of cracked cylinder head

1. Knocking in the cylinder
2. Jacket cooling water pressure fluctuates
3. Jacket cooling water temperature fluctuates
4. Expansion tank level may drop
5. Sparks from funnel