3306C Truck Engine Caterpillar

Excessive Engine Oil Consumption - Inspect

Usage:

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.

Excessive oil leakage from the crankcase breather can be caused by combustion gas leakage around the pistons. A dirty crankcase breather will cause high pressure in the crankcase, and a dirty crankcase breather can cause the gaskets and the seals to leak.

Excessive oil leakage from the crankcase breather can also be caused by an oil level in the oil pan that is too high. This condition results in a crankshaft that drips oil. Take extra care to maintain the oil level under these conditions:

The engine has been stopped.
The oil has been allowed to settle for about 20 minutes.

See the Operation and Maintenance Manual, "Model View Illustrations" for information on the location of the oil level gauge.

Oil Leakage Into Combustion Area Of Cylinders

Oil leakage into the combustion area of the cylinders can be the cause of both blue smoke and excessive oil consumption. There are five possible ways for oil to leak into the combustion area of the cylinders:

Oil leakage between worn valve guides (inlet) and valve stems
Worn piston components or damaged piston 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
Improper seating of the rings for a new engine or a rebuilt engine

Too much 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.

Note: Excessively worn engine components and damaged engine components can be the result of any one of the following conditions:

Improper maintenance of the oil
Incorrect fuel system settings
Poor maintenance of the air filter

Note: See these following publications:

Operation and Maintenance Manual, "Engine Oil and Filter - Change"
"TMI"
Operation and Maintenance Manual, "Engine Air Service Cleaner Indicator - Inspect"

Measuring Engine Oil Pressure

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

The engine oil pressure and a restriction in the oil filter can be measured with the electronic service tool.

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

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Illustration 1	g00296486
1U-5470 Engine Pressure Group

The 1U-5470 Engine Pressure Group measures the oil pressure in the system. This Engine Pressure Group has a gauge that monitors 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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Illustration 2	g00323033
Location of Oil Pressure Switch (1) Oil pressure switch.

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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). With the engine at operating temperature, the minimum oil pressure at full load rpm should be approximately 250 kPa (36 psi). Minimum oil pressure at low idle rpm should be approximately 100 kPa (14 psi).

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Illustration 3	g00296494
Engine Oil Pressure Graph

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 to NOT 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 open, the lubrication system can not reach the maximum pressure. Oil pump gears with too much wear cause a reduction in oil pressure.

Oil Filter Bypass Valve

If the bypass valve for one or more of the oil filters is held open due to a restriction, a reduction in the oil pressure can be the result. Remove each bypass valve and clean each bypass valve. This allows you to correct the 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 too much bearing clearance can cause low oil pressure. Low oil pressure can also be caused by an oil line or by an oil passage that is open, broken, or disconnected.

Piston Cooling Jets

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