What is the function of the oil pump relief valve and how is it tested?

What is the function of the oil pump relief valve and how is it tested?

• A. Maintains oil temperature by circulating through a cooler; tested by heat test.
• B. Controls maximum oil pressure; test by applying oil pressure to valve and confirming opening at specified pressure.
• C. Filters contaminants from oil before it reaches the bearings; tested by filter differential pressure.
• D. Drives the pump gearing; test by torque measurement.

Answer: (B)

The oil pump relief valve sets and limits the maximum oil pressure in the lubrication system. When pressure reaches its preset value, the valve opens to bypass excess oil back to the pump or sump, preventing over‑pressurizing the bearings, galleries, and seals and helping keep a stable, safe lubrication pressure. To test it, you apply a known oil pressure to the valve from a calibrated source and verify that it opens at the specified pressure. Observe the opening pressure with a gauge as you increase pressure, then confirm it closes again when pressure is reduced and that the bypass path functions correctly. Check for smooth operation with no sticking, and ensure there are no leaks around the valve and that it reseats properly when pressure falls. If the relief valve doesn’t open at the correct pressure, or sticks/leaks, oil pressure can be incorrect, leading to too-low lubrication or potential damage. Circling back to the other descriptions: circulating through a cooler relates to cooling, filtering involves removing contaminants, and driving the pump gearing concerns the drive mechanism—none of these describe the relief valve’s function.

The oil pump relief valve sets and limits the maximum oil pressure in the lubrication system. When pressure reaches its preset value, the valve opens to bypass excess oil back to the pump or sump, preventing over‑pressurizing the bearings, galleries, and seals and helping keep a stable, safe lubrication pressure.

To test it, you apply a known oil pressure to the valve from a calibrated source and verify that it opens at the specified pressure. Observe the opening pressure with a gauge as you increase pressure, then confirm it closes again when pressure is reduced and that the bypass path functions correctly. Check for smooth operation with no sticking, and ensure there are no leaks around the valve and that it reseats properly when pressure falls. If the relief valve doesn’t open at the correct pressure, or sticks/leaks, oil pressure can be incorrect, leading to too-low lubrication or potential damage.

Circling back to the other descriptions: circulating through a cooler relates to cooling, filtering involves removing contaminants, and driving the pump gearing concerns the drive mechanism—none of these describe the relief valve’s function.