B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 007-999   Lubricating Oil System – Overview

The specification for Cummins alternative fuel midrange engines are:

B5.9G/LPG Engines

• Conforms to CES20074; this should be identified on the supplier’s oil packaging. If you are
not sure if the oil that you are currently using meets the Cummins specification, you should contact your supplier to obtain a copy of their letter of registration from Cummins that certifies that their oil meets the specification. For easy identification, the packaging of the oil should show CES20074 on it.

Special “break-in” oils are
not recommended for use in new or rebuilt Cummins engines. Use the same lubricating oil that will be used in normal engine operation. Synthetic or partially synthetic engine oils, however, can
not be used in a new or rebuilt engine during break-in. Use a standard petroleum-based oil for the first drain interval.

CAUTION  A sulfated ash limit of 0.5 percent has been placed on all engine lubricating oils recommended for use in Cummins alternate fueled engines. Higher ash oils can cause valve and/or piston damage and lead to excessive oil consumption and degradation of the catalyst.

For further details and discussion of engine lubricating oils for Cummins engines, refer to Cummins Engine Oil Recommendations, Bulletin
3810340.

When diagnosing lubrication system malfunctions, check all obvious items related to oil pressure, such as gauges, high and low oil level, excessive oil contamination, and oil viscosity.

High oil pressure usually occurs after the engine is first started in cold weather. Cold start oil pressure typically will be approximately 552 to 689 kPa [80 to 100 psi]. If the pressure regulator plunger is operating properly, the oil pressure should drop back to approximately 449 kPa [65 psi]
when normal operating temperature is reached.

The engine will have high oil pressure at normal operating temperature if the regulator sticks in the closed position. Check the regulator for freedom of movement. Refer to Procedure
007-029.

Low lubricating oil pressure (or no oil pressure) can be caused by several lubrication system-related malfunctions. To begin the investigation, determine
the engine operating conditions when the low pressure was first observed;
for example, following a service interval, at idle
only, while operating on a steep grade.

High oil level can cause low oil pressure. If the oil level is high enough for the connecting rods to dip into during operation, the oil can become aerated, resulting in low oil pressure.

Low lubricating 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.

A plugged filter will cause a gradual loss of oil pressure by approximately 69 kPa [10 psi]. The pressure will return to normal when the filter bypass valve opens. If
not corrected, this will result in severe engine wear, as the engine is running on unfiltered oil when the bypass valve is open.

Check the lubricating oil gauge and sending unit to make sure they are operating correctly by verifying the pressure with a manual gauge.

A loose suction tube, damaged gasket, or crack in the suction tube can cause a temporary loss of prime for the oil pump. The engine will have low
pressure or no oil pressure at starting, followed by normal oil pressure.

A steady decrease in oil pressure over a long period of time can be an indication of worn bearings or excessive oil pump wear.

The capacity of the six-cylinder oil pump is greater than the four-cylinder. If low or high pressure occurs after changing the pump, verify that the correct pump was used. Refer to Procedure
007-031.

A – Four-Cylinder
  • 12.947 mm [0.510 in]

B – Six-Cylinder
  • 17.947 mm [0.707 in]

CAUTION  Diluted oil can cause severe engine damage.

Check the condition of the lubricating oil.

• Green discoloration is an indication of coolant in the lubricating oil.
• Milky discoloration is an indication of condensation in the lubricating oil pan. If this clears up when the engine is warm, then it is normal.

Coolant in the oil can be caused by:

• Expansion plugs leaking
• Lubricating oil cooler element leaking
• Damaged cylinder head or gasket
• Cracked engine block
• Casting porosity.

Since the lubricating oil cooler design does
not require gaskets or seals to maintain the separation of oil and coolant, the element itself
must leak to allow mixing of the fluids. Refer to Procedure
007-003.

During operation, the lubricating oil pressure will be higher than coolant pressure. A leak in the lubricating oil cooler will show as lubricating oil
in the coolant.

However, following an engine shutdown, the residual pressure in the coolant system can cause coolant to seep through the leak path and into the lubricating oil.

To check for leaks, pressurize the cooling system to 140 kPa [20 psi]. With the system pressurized, remove the following components and inspect for leaks:

• Valve covers (leaks indicate cracked head)
• Lubricating oil drain plug (leaks indicate defective lubricating oil cooler, head gasket, or cracked head or block)
• Tappet cover (expansion plug leak).

Coolant in the lubricating oil can be caused by a damaged cylinder head gasket or cracked cylinder head or block.

Remove the cylinder head and gasket and inspect for cracks or damage.

Various gaskets, seals, and plugs are used to contain the lubricating oil. Most leaks can be identified during routine inspection of the engine
and vehicle.

A blown expansion plug can allow a relatively large quantity of lubricating oil to escape, resulting in a sudden drop in the lubricating oil pressure.

When checking for such a leak, be sure to check the expansion plug behind the tappet cover, as well as those that can be obscured by chassis parts.

Lubricating oil blowing out the breather is a sign of a blown expansion plug.

If the lubricating oil cooler element ruptures, the lubricating oil pressure will force lubricating oil into the coolant system. Lubricating oil
in the coolant should be visible when the radiator cap is removed. Refer to Procedure
007-003.

Worn or damaged seals in the turbocharger can also allow lubricating oil to leak into the air intake piping and be burned in the engine.

The condition can be verified by removing the charge air cooler tubing and looking for oil.

Inadequate sealing of the piston rings will result in excessive lubricating oil being blown into the closed-crankcase ventilation system and/or consumed by the engine. Refer to Procedure
014-002.

Lubricating oil can also be lost through a worn or malfunctioning air compressor. Look for carbon buildup in the air line from the compressor to
the air tank. Also, a failed air compressor head or head gasket can allow oil to leak into the coolant or coolant to leak into the oil during hot shutdown.