Which type of engine block is most likely to have coolant contamination of the crankcase due to a leaking liner O-ring?

A wet sleeve engine block is designed with removable cylindrical liners that hold the engine's cylinders. These liners are commonly sealed into the engine block with O-rings or gaskets. In the case of a leak, the coolant can easily seep past the O-ring and into the crankcase because the wet sleeves are in direct contact with the coolant. This design allows for easier replacement of the liners but also makes them more susceptible to issues like O-ring failures, leading to coolant contamination in the crankcase.

In contrast, a solid block engine does not have removable liners; it is a single cast piece with the cylinders formed directly into the block. This design does not introduce the same risk of coolant entering the crankcase through an O-ring since there are no sleeves to leak. Dry sleeve blocks have liners that do not contact the coolant directly, so any failure in sealing would not result in coolant entering the crankcase through the liner O-rings. Lastly, the cylinder head, while it has its own sealing points, is not directly relevant to the issue of liner O-rings and crankcase contamination, as it deals primarily with the combustion chamber.