ASE A1 Engine RepairGeneral Engine DiagnosisMedium
A technician is performing an engine oil pressure test. The specification is 40-60 psi at operating temperature and 2000 RPM. The gauge reads a steady 15 psi. Which of the following is the most likely cause?
- AA clogged oil filter
- BA faulty oil pressure sensor
- CWorn main or rod bearings
- DAn overfilled crankcase
Show answer & explanationAnswer & explanation
Correct answer: C. Worn main or rod bearings
Consistently low oil pressure, especially at higher RPMs, often indicates excessive clearance in the engine's main or rod bearings, allowing oil to escape too easily.
Why the other options are wrong
- A. A clogged oil filter would more likely cause a bypass valve to open, or potentially restrict flow, but severe, steady low pressure usually points to internal leakage.
- B. A faulty oil pressure sensor would likely give an erratic reading or a 'no pressure' warning, but not a steady, very low reading if mechanical pressure is actually low.
- D. An overfilled crankcase can cause oil foaming and aerated oil, potentially leading to lower pressure, but typically not as severe or consistent as 15 psi when spec is 40-60.
Low Oil Pressure Diagnosis
Low oil pressure indicates a problem in the lubrication system, potentially leading to engine damage. Common causes include worn bearings or a faulty oil pump.
- Crucial for engine lubrication and cooling
- Low pressure can cause severe engine wear
- Worn bearings are a common mechanical cause
Memory trick: When oil pressure drops, think 'Bearings or Pump' first!