FAA Aviation Mechanic Powerplant (AMP)Engine InspectionMedium
A mechanic inspecting a turbocharger finds excessive radial and axial play when moving the compressor wheel shaft by hand, along with light rub marks on the compressor housing. This condition most likely indicates:
- AA cracked turbine housing
- BWorn or failing turbocharger bearings
- CAn overboost condition from the wastegate
- DExcessive exhaust back pressure
Show answer & explanationAnswer & explanation
Correct answer: B. Worn or failing turbocharger bearings
Excessive shaft play combined with housing rub marks is a classic symptom of worn or failing turbocharger center bearings, which allow the shaft to move out of its normal rotational axis and contact the housing.
Why the other options are wrong
- A. A cracked housing would show visible fracture lines, not shaft play.
- C. An overboost condition relates to boost pressure control, not shaft play.
- D. Back pressure affects exhaust flow, not bearing clearance or shaft movement.
Turbocharger Bearing Wear
Excessive radial/axial shaft play in a turbocharger indicates worn center bearings, which can lead to wheel-to-housing contact and eventual failure.
- Checked by hand-moving the shaft radially and axially
- Rub marks on housing confirm bearing wear
- Oil starvation/contamination is a common cause
- Left unaddressed, can lead to catastrophic turbo failure
Memory trick: 'Wobbly Wheel, Worn Bearing' — play in the shaft means the bearing is going bad.