The worst possible scenario happened!
After the condition did not improve after cleaning the exhaust elbow i contacted the mechanic.
At first, he thought it was the injectors, and yes, none of the three injectors were working properly. He ordered new nozzles and replaced them.
He turned the pistons and noticed antifreeze in the cylinders! We hoped that only the gasket was damaged, but the cylinder head has cracks in three places.
Cylinder liner has erosion damage, but this can be solved by replacing the cylinder liner.
The idea is that we go for a complete repair of the engine, pistons, bearings, valves, cylinder liners, cylinder head...
The only problem is that I can't find the cylinder head. Do you know where it could be purchased, does anyone produce a cylinder head for the Volvo Penta 2030D?