During overhaul, which parameter is commonly checked to verify journal bearing clearance is within spec?

• A. Oil clearance measured by bore wear and direct measurement.
• B. Outer casing temperature.
• C. Electrical resistance of bearing.
• D. Humidity inside the engine.

Answer: (A)

Oil clearance is the key parameter for journal bearings because it determines whether a lubricating film can form properly between the rotating journal and the bearing bore. During overhaul, this clearance is verified by directly measuring the actual gap: you assess bore wear and measure the journal, then calculate the oil clearance from the difference between the journal diameter and the bearing bore diameter. If bore wear has widened the bore or the journal is undersized, the clearance will drift outside spec, risking insufficient oil film or metal-to-metal contact. Temperature, electrical resistance, or humidity inside the engine don’t provide a direct, reliable measure of this critical gap, so the direct measurement approach is the standard method to confirm the bearing clearance is within specification.