The camshaft is replaced in the following cases:

Four molded gaskets are installed between the flanges of the cylinder head and the intake pipe

The piston of the 1st cylinder is set to the TDC (top dead center) position of the compression stroke so that when carrying out work related to the removal of the camshaft drive belt, the valve timing is not disturbed

If an oil leak through the oil sump seal cannot be eliminated by tightening its fastening bolts, it means that the seal is severely deformed and must be replaced