Engine Lubrication System – Inspect and adjust


Low Oil Pressure

The following conditions will cause low oil pressure.
• The oil level is low in the crankcase.
• A restriction exists on the oil suction screen.
• Connections in the oil lines are leaking.
• The connecting rod or the main bearings are worn.
• The rotors in the oil pump are worn.
• The oil pressure relief valve is operating incorrectly.
A worn oil pressure relief valve can allow oil to leak through the valve which lowers the oil pressure. When the engine runs at the normal temperature for operation and at high idle, the oil pressure must be a minimum of 280 kPa (40 psi). A lower pressure is normal at low idle. A suitable pressure gauge can be used in order to test the pressure of the lubrication system.

High Oil Pressure

High oil pressure can be caused by the following conditions.
• The spring for the oil pressure relief valve is installed incorrectly.
• The plunger for the oil pressure relief valve becomes jammed in the closed position.
• Excessive sludge exists in the oil which makes the viscosity of the oil too high.

Engine Oil Pump Inspect

If any part of the oil pump is worn enough in order to affect the performance of the oil pump, the oil pump must be replaced. Perform the following procedures in order to inspect the oil pump.


Remove the oil pump from the engine. Remove the cover of the oil pump.
Remove the outer rotor (1). Clean all of the parts. Look for cracks in the metal or other damage. Install the outer rotor. Measure the clearance of the outer rotor to the body.

Clearance for the inner rotor body

Measure the clearance of the inner rotor to the outer rotor (2).

End play measurement of the rotor

Measure the end play of the rotor with a straight edge and a feeler gauge (3).
Clean the top face of the oil pump and the bottom face of the cover. Install the cover on the oil pump. Install the oil pump on the engine.

Excessive Bearing Wear Inspect

When some components of the engine show bearing wear in a short time, the cause can be a restriction in an oil passage. An engine oil pressure indicator may show that there is enough oil pressure, but a component is worn due to a lack of lubrication. In such a case, look at the passage for the oil supply to the component. A restriction in an oil supply passage will not allow enough lubrication to reach a component. This will result in early wear.

Engine Oil Leaks on the Outside of the Engine

Check for leakage at the seals at each end of the crankshaft. Look for leakage at the gasket for the engine oil pan and all lubrication system connections. Look for any engine oil that may be leaking from the crankcase breather. This can be caused by combustion gas leakage around the pistons. A dirty crankcase breather will cause high pressure in the crankcase. A dirty crankcase breather will cause the gaskets and the seals to leak.

Engine Oil Leaks into the Combustion Area of the Cylinders

Engine oil that is leaking into the combustion area of the cylinders can be the cause of blue smoke. There are several possible ways for engine oil to leak into the combustion area of the cylinders:
• Failed valve stem seals
• Leaks between worn valve guides and valve stems
• Worn components or damaged components (pistons, piston rings, or dirty return holes for the engine oil)
• Incorrect installation of the compression ring and/or the intermediate ring
• Leaks past the seal rings in the turbocharger shaft
• Overfilling of the crankcase
• Wrong dipstick or guide tube
• Sustained operation at light loads
Excessive consumption of engine oil can also result if engine oil with the wrong viscosity is used. Engine oil with a thin viscosity can be caused by fuel leakage into the crankcase or by increased engine temperature.

Increased Engine Oil Temperature - Inspect

Look for a restriction in the oil passages of the oil cooler. The oil temperature may be higher than normal when the engine is operating. In such a case, the oil cooler may have a restriction.