Major mechanical damage has occurred but there are silver metallic flakes that the magnet does not pick up; what is the likely source?

• A. Lifters
• B. Valves
• C. Cylinder walls
• D. Pistons

Answer: (D)

This question tests how to interpret debris that a magnet does not attract. A magnet will grab ferrous (iron-containing) particles, so non-ferrous debris points to different materials. Silver-colored flakes that aren’t magnetic suggest aluminum alloy, which is used in pistons. In contrast, lifters, valves, and cylinder walls are typically steel or cast iron (ferrous), so debris from those parts would usually be magnetic. Since the flakes are non-magnetic and silver, the most likely source is the piston material shedding under major damage.