Oil Pressure Test

Check for proper oil pressure at the sending unit passage with an externally mounted mechanical oil pressure gauge. A tachometer may also be needed, as some specifications may require running the engine at a specific RPM.

1. While the engine is cold, locate and remove the oil pressure sending unit.
2. Following the manufacturer’s instructions, connect a mechanical oil pressure gauge and, if necessary, a tachometer to the engine.
3. Start the engine and allow it to idle.
4. Note and record the oil pressure reading when the engine is cold. The engine may need to run at a specified RPM, if so check the vehicle's specification.
5. Run the engine until normal operating temperature is reached.
6. Check the oil pressure reading again with the engine hot and record the value. Turn off the engine.

Compare the hot oil pressure reading to the specification. If the reading is low, check the cold pressure reading against the specification. If the cold pressure is well above the specification, and the hot reading was lower than the specification, the engine may have the wrong viscosity oil. Change the oil, making sure to use the proper grade and quantity, and then repeat the test.

Low oil pressure readings could be attributed to internal component wear, pump related problems, a low oil level, or oil viscosity that is too low. High oil pressure readings could be caused by an overfilled crankcase, too high of an oil viscosity or a faulty pressure relief valve.