Question 19 OSE01 - Chief Engineer - OSV

The Correct Answer is B **Explanation for Option B (Correct):** The purpose of the air filter element is to trap contaminants (dust) and prevent them from entering the engine intake manifold. When an air filter system is improperly sealed—specifically, if the gasket fails to seal the filter element against the housing—air will bypass the filter medium, taking the path of least resistance. Dust-laden air (from the "dirty" side) will leak past the faulty seal and enter the "clean" side of the housing and potentially streak the element itself on the side facing the engine. Visual evidence of dust or streaks of dirt on the "clean" side of the filter element (the side facing the turbocharger/engine intake) is the primary indication that air has bypassed the filtering medium and that the engine has been exposed to unfiltered dust. **Explanation of Why Other Options are Incorrect:** * **A) The "dirty" side of the air filter housing is coated with dust:** This is a normal condition. The air filter housing is designed to collect dusty ambient air on the "dirty" side (upstream of the filter element). A coating of dust here simply confirms the filter is doing its job of separating the dirty air from the clean air before filtration. * **C) The "dirty" side of the air filter element is coated with dust:** This is also a normal and expected condition. The filter element traps the dust, meaning the "dirty" side (the intake side of the element) should be coated with the filtered contaminants. * **D) The "clean" side of the air filter element is clean and free of dust:** This indicates that the filter is working perfectly and the seal is intact, meaning no unfiltered air has bypassed the element. This contradicts the scenario presented in the question (suspecting contamination due to improper sealing).