CYLINDER HEAD CRACKS
This is an experience with a 6RTA48 Mitsubishi Sulzer Diesel.
Onboard we used to face a series of cylinder head cracks on each of the units within a short period.
The cracks were occurring closer to the fuel valve pockets, airstart valve pockets and indicator cock pocket. Initially it was suspected that this was due to the improper injection of fuel valves thereby causing errors around the pocket, which would have weakened the area in the vicinity.
This problem was later found to be occurring on sister vessels too and the makers came to a conclusion that it was due to a manufacturing defect and advised the company to renew the heads, which was done, and the problem resolved.