ASE A1 Engine RepairEngine Block AssemblyMedium
A client's engine exhibits persistent low oil pressure, even after replacing the oil pump and ensuring the correct oil viscosity. A technician suspects an issue within the engine block assembly. Which of the following is the MOST likely cause?
- AExcessive crankshaft end play.
- BA clogged oil filter.
- CExcessive main bearing oil clearance.
- DWorn camshaft bearings.
Show answer & explanationAnswer & explanation
Correct answer: C. Excessive main bearing oil clearance.
Excessive main bearing oil clearance allows too much oil to leak out from between the journals and bearings, leading to a significant drop in overall engine oil pressure. While other factors can cause low oil pressure, this is a common internal engine block issue.
Why the other options are wrong
- A. Excessive crankshaft end play primarily affects the thrust bearing and axial movement, not typically overall oil pressure.
- B. A clogged oil filter would restrict oil flow, potentially causing the bypass valve to open, but wouldn't directly cause persistently low pressure in the main galleries unless bypass failed or flow was severely restricted, which is less likely than excessive bearing clearance for a persistent low pressure issue.
- D. Worn camshaft bearings can contribute to low oil pressure, but excessive main bearing clearance often has a more significant impact due to the larger surface area and flow.
Excessive Bearing Clearance & Oil Pressure
Excessive clearance in main or connecting rod bearings allows too much oil to escape, reducing the resistance to oil flow and causing a drop in engine oil pressure.
- Main bearings are a primary contributor to overall engine oil pressure regulation.
- Even slightly oversized clearance can significantly impact pressure.
- Requires engine disassembly and replacement of bearings (and possibly crankshaft machining) to correct.
Memory trick: Clearance 'C'auses 'C'ritical pressure drop.