Lubrication System: Inspection

Lubricating Oil Pressure

1. When diagnosing lubricating system malfunctions, check all obvious items related to oil pressure, such as gauges, high and low oil level, excessive oil contamination, and oil viscosity.
2. High lubricating oil pressure occurs after the engine is first started in cold weather. Cold start oil pressure typically will be approximately 689 - 827 kPa (7.03 - 8.44 kg/cm ² , 100 - 120 psi). If the pressure regulator plunger is operating properly, the oil pressure is between 310 - 379 kPa (3.16 - 3.87 kg/cm ² , 45 - 55 psi) when normal operating temperature is reached.
3. The engine will have high oil pressure at normal operating temperature if the oil pressure regulator valve sticks in the closed position.

   Check the regulator for freedom of movement. Refer to Removal and Installation .

4. Low engine oil pressure (or no oil pressure) can be caused by several lubricating system related malfunctions. To begin the investigation, determine the engine operating conditions when the low pressure was first observed. The following are conditions of low lubricating oil pressure:
   • At idle only. 
   • Operating on a steep grade.
5. High engine oil level can cause low oil pressure. If the engine oil level is high enough for the connecting rods to dip into the oil while operating, the oil can become aerated, resulting in low oil pressure.
6. Low oil level will not  normally appear as low oil pressure. Typically, it will appear as an intermittent loss of oil pressure when rounding a corner or operating on a steep grade. This condition exists when the oil level is extremely low and the suction tube can not  pick up oil during all modes of operation.
7. A plugged oil filter will cause a gradual loss of oil pressure by approximately 69 kPa (0.70 kg/cm ² , 10 psi). The pressure will return to normal when the oil filter bypass valve opens. If not  corrected, this will result in severe engine wear, as the engine is running on unfiltered oil when the oil filter bypass valve is open.
8. Verify the pressure with a manual gauge to make sure the lubricating oil gauge and the sending unit are operating correctly.

   Courtesy of NISSAN NORTH AMERICA, INC.

   • To check the engine oil pressure, remove the oil pressure switch from the engine block. Refer to Removal and Installation .
   • Install and tighten tool (1) into the oil pressure switch port in the cylinder block.
   • Install the oil pressure switch (2) onto the tool. Hold the tool with a suitable tool and tighten the oil pressure switch.
   • Install and tighten tool (3) into the side of the tool.
   • Operate the engine to measure engine oil pressure with the tool.
   • After confirming with the tool that the vehicle oil gauge and the sending unit are operating properly, remove the tool and reinstall the oil pressure switch. Refer to Removal and Installation .
9. A loose oil suction tube, damaged gasket, or crack in the suction tube can cause a loss of prime for the oil pump. The engine will have low pressure or no oil pressure during starting, followed by normal oil pressure.
10. A steady decrease in oil pressure over a long period can be an indication of worn bearings or excessive oil pump wear.