Counterman A says "MLS" (Multi-Layer Steel) head gaskets require a very smooth surface to seal properly. Counterman B says a common cause of head gasket failure is engine overheating. Who's right?

Both Counterman A and Counterman B are correct regarding their statements about MLS head gaskets and head gasket failure causes.

MLS (Multi-Layer Steel) head gaskets indeed require a very smooth surface to create an effective seal. The design of these gaskets focuses on the ability to withstand high temperatures and pressures, but they depend on a flawless mating surface. Any imperfections, such as roughness or warping, can compromise the seal, leading to engine performance issues or coolant leaks.

Additionally, Counterman B's assertion about engine overheating being a common cause of head gasket failure is also accurate. Overheating can cause the head gasket to expand beyond its limits, leading to failure of the material, or it can warp the cylinder head or engine block, further compromising the ability of the head gasket to maintain a seal. This overheating can occur due to several factors, including coolant loss, malfunctioning thermostats, or pump failures.

Both perspectives highlight crucial aspects of engine maintenance and the importance of proper installation and operation to prevent head gasket issues.