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Reciprocating Connecting Rod Bearing Scoring — Insufficient Oil Pressure

Likely causes

Oil pressure below 0.15 MPa — oil pump wear prevents oil film formation

Check: Direct-connect oil pressure gauge — normal: net oil pressure 0.2~0.4 MPa (excluding suction pressure). Stop immediately if below 0.15 MPa within 30 seconds of startup

What to do: Replace oil strainer and filter (immediately if clogging ≥60%) → flush crankshaft oil passages with N₂ in reverse → replace connecting rod bearing metal (crank pin OD roundness within 0.01 mm) → run 1,000 hours clean oil break-in after overhaul

Oil contamination — ISO cleanliness class exceeds 16/14/11, metal particles ≥15µm present

Check: Take oil sample → iron particle count (target: less than 10 particles/mL for ≥15µm). When replacing filter, record and compare metal powder content

What to do: Full oil replacement → clean oil strainer → re-sample after 48 hours operation to re-confirm cleanliness

Field tip

After bearing replacement, oil pressure normalization at first start takes up to 30 seconds — stop immediately and re-investigate if below 0.15 MPa within 30 seconds. If crank pin is severely worn, replace crankshaft too.

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