Question 33

The Correct Answer is C **Why option C ("Aluminum dust residue") is correct:** Roots-type blowers commonly use aluminum alloy casings and impellers (rotors) due to their light weight and favorable thermal properties. The presence of aluminum dust residue in the air boxes—which are downstream of the blower and upstream of the engine cylinders—is a direct, undeniable indication that the blower's internal components (the rotors or the casing itself) are physically grinding against each other. This catastrophic wear means the critical clearances within the blower have failed, resulting in immediate self-destruction. The blower is likely no longer providing adequate air flow, and its total failure is imminent, requiring immediate replacement to prevent further engine issues (like high thermal stress, poor combustion, and eventual turbocharger surging or failure if the engine is turbocharged). **Why the other options are incorrect:** * **A) Iron dust residue:** While any metallic dust indicates wear, Roots blowers primarily use aluminum components. Iron dust is more characteristic of wear in gears, bearings, or possibly the engine cylinder itself (piston rings/liners). While unwanted, it is not the classic, critical indicator of immediate catastrophic internal failure of the aluminum blower components. * **B) Oil accumulations:** Some oil accumulation is normal. Roots blowers have internal bearings and gears that require lubrication. While excessive oil carry-over might indicate failing oil seals, it typically leads to reduced efficiency and fouling, not the immediate, catastrophic mechanical failure signaled by grinding aluminum. * **D) Water accumulations:** Water accumulation, often condensation or carry-over from a cooler (if fitted), indicates a drainage problem or cooler leak. While detrimental to the blower's efficiency and potentially causing corrosion, it does not signify immediate, complete mechanical failure of the rotating components like aluminum dust does.