Question 28Motor Plants - 1st Asst/Chief

The correct answer is B) seal against scavenge air leakage. The top gland where the piston rod exits the cylinder is designed to seal against the leakage of scavenge air, which is the air that is used to purge the cylinder and remove the exhaust gases. This seal is necessary to maintain the proper air/fuel mixture and combustion efficiency within the engine. The other answer choices are incorrect because: A) the crankcase oil leakage is typically sealed by the crankshaft seals, not the piston rod gland; C) and D) the piston rod gland does not directly maintain the crankcase vacuum or pressure, which are controlled by other engine components.