An engine overhaul can be classified into two.

Minor Overhaul: It is like a localized repair pertaining to a particular system. Eg: A repair/replacement of Lube oil pump, a Water pump repair with the help of a repair kit.
Major Overhaul: When many engine systems of involved and considerable dismantling, repair/replacement and assembling is required, we use the term Major overhaul. Activities like reconditioning of Cylinder head, replacement of Cylinder components(Liners, Pistons, piston rings) or re-boring in case of liner less engines.
In case of a complete overhaul, all of the 5C components will be evaluated for abnormalities and will be repaired or replaced as per requirement. The 5C components being Cylinder block, Cylinder head, Crankshaft, Camshaft, Con-rods. Apart from the above critical components, individual systems will also be checked and attended as per the situation. Eg: The Fuel injectors may require replenishment.

All the above activities will be accompanied with the usage of Seals and Joints wherever it is applicable.