C-10 and C-12 Truck Engines Caterpillar


Lubrication System

Usage:

C-12 1YN
One of the problems in the list that follows will generally be an indication of a problem in the lubrication system for the engine.

  • Excessive oil consumption

  • Low oil pressure

  • High oil pressure

  • Excessive wear of the bearings

  • Increased oil temperature

Excessive Oil Consumption

Oil Leakage On Outside Of Engine

Check for leakage at the seals at each end of the crankshaft. Look for leakage at the oil pan gasket and all lubrication system connections. Look for any 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.

Oil Leakage Into Combustion Area Of Cylinders

Oil leakage into the combustion area of the cylinders can be the cause of blue smoke. There are four possible ways for oil leakage into the combustion area of the cylinders:

  • Oil leakage between worn valve guides and valve stems

  • Worn components or damaged components (pistons, piston rings, or dirty oil return holes)

  • Incorrect installation of the compression ring and/or the intermediate ring

  • Oil leakage past the seal rings in the impeller end of the turbocharger shaft

Excessive oil consumption can also be the result if oil with the wrong viscosity is used. Oil with a thin viscosity can be caused by fuel leakage into the crankcase or by increased engine temperature.

Measuring Engine Oil Pressure

First, check the oil pressure electronically by using the electronic technician. The engine oil pressure and a restriction in the oil filter can be measured with the electronic service tool.

Table 1
Tools Needed    
Part Number     Part Name     Quantity    
1U-5470     Engine Pressure Group     1    

An oil pressure gauge that has a defect can indicate low oil pressure or high oil pressure.




Illustration 1g00296486

1U-5470 Engine Pressure Group

The 1U-5470 Engine Pressure Group measures the oil pressure in the system. This engine tool group can read the oil pressure inside the oil manifold.

Note: Refer to Special Instruction, SEHS8907 for more information on using the 1U-5470 Engine Pressure Group.




Illustration 2g00437624

Oil gallery plug

(1) Plug

------ WARNING! ------

Work carefully around an engine that is running. Engine parts that are hot, or parts that are moving, can cause personal injury.

----------------------

Oil pressure to the camshaft and main bearings should be checked on each side of the cylinder block at oil gallery plug (1). Install the 1U-5470 Engine Pressure Group into this opening. Run the engine with SAE 15W40 oil. While the engine is at operating temperature, the minimum oil pressure at full load rpm should be approximately 275 to 414 kPa (40 to 59 psi). Minimum oil pressure at low idle rpm (600 to 800 rpm) should be approximately 68 kPa (10 psi).

Low Oil Pressure

Crankcase Oil Level

Check the level of the oil in the crankcase. Add oil if oil is needed. The oil level can possibly be too far below the oil pump supply tube. This will cause the oil pump not to have the ability to supply enough lubrication to the engine components.

The Oil Pump Does Not Work Correctly

The inlet screen of the supply tube for the oil pump can have a restriction. This restriction will cause cavitation and a loss of oil pressure. Air leakage in the supply side of the oil pump will also cause cavitation and loss of oil pressure. If the bypass valve for the oil pump is held in the open position, the lubrication system can not reach the maximum pressure. Oil pump gears that have too much wear will cause a reduction in oil pressure.

Oil Filter Bypass Valve

If the bypass valve for one or more of the oil filters is held in the open position due to a restriction, a reduction in the oil pressure can be the result. Remove each bypass valve and clean each bypass valve in order to correct this problem. You must also clean each bypass valve bore. Install new Caterpillar oil filters. New filters will prevent more debris from causing this problem.

Excessive Clearance At Engine Bearings Or Open Lubrication System

Components that are worn and components that have excessive bearing clearance can cause low oil pressure. Low oil pressure can also be caused by an oil line or an oil passage that is open, broken, or disconnected.

Piston Cooling Jets

While the engine is operating, the piston cooling jets direct oil toward the bottom of the piston in order to cool the piston. This also provides lubrication for the piston pin. A seizure of the piston will occur quickly if a piston cooling jet experiences any of the following problems:

  • Breakage

  • Restriction

  • Incorrect installation

High Oil Pressure

Oil pressure will be high if the bypass valve for the oil pump can not move from the closed position.

Excessive Wear of the Bearings

When some components of the engine show bearing wear in a short time, the cause can be a restriction in an oil passage.

An indicator for the oil pressure 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.

Increased Oil Temperature

When the engine is at operating temperature and you are using SAE 15W40 oil, the maximum oil temperature is 110 °C (230 °F). This is the temperature of the oil after passing through the oil cooler.

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. A restriction in the oil cooler will not cause low oil pressure in the engine.

Determine if the oil cooler bypass valve is held in the open position. This condition will allow the oil to pass through the valve instead of the oil cooler. The oil temperature will increase.

Oil Pressure Indicators

Table 2
Tools Needed    
Part Number     Part Name     Quantity    
1U-5470     Engine Pressure Group     1    

An oil pressure indicator that has a defect or a sender that has a defect can give an indication of a low oil pressure or a high oil pressure.

The 1U-5470 Engine Pressure Group can be used in order to compare the indicators on the instrument panel and the oil pressure that is displayed on the electronic service tool.

The 1U-5470 Engine Pressure Group measures the oil pressure in the system. This engine tool group has a gauge that reads the oil pressure inside the oil manifold.

Note: Refer to Special Instruction, SEHS8907 for more information on using the 1U-5470 Engine Pressure Group .

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