Oil System Over View

Lubricating Oil System - Overview Page 1 of 13
007-999 Lubricating Oil System - Overview
General Information
WARNING
Some state and federal
agencies have determined
that used engine oil can be
carcinogenic and can cause
reproductive toxicity. Avoid
inhalation of vapors,
ingestion, and prolonged
contact with used engine oil.
If not reused, dispose of in
accordance with local
environmental regulations.
WARNING
To reduce the possibility of
personal injury, avoid direct
contact of hot oil with your
skin.
Cummins Inc. recommends the

use of a high-quality SAE 15W-
40 heavy-duty engine oil, such
as Cummins Premium Blue®,
which meets the American
Petroleum Institute (API)
performance classification
CI/SK.
NOTE: The SK designation is

required for B series
engines. This is due to the
fact that all B series engines
use sliding tappets.
mk:@MSITStore:C:\Users\jorispc\Downloads\Quick%20Serve%20DVD\MR_D.CHM::/e... 08-Mar-19
NOTE: If CI/SK oils are not

available, see the appropriate
Operation and Maintenance
manual for your engine for
alternatives.
CAUTION
Limited use of low-viscosity

lubricating oils, such as
10W-30, can aid in starting
the engine and providing
sufficient lubricating oil flow
at ambient temperatures
below -5°C [23°F] as shown
in the illustration. However,
the continuous use of low-
viscosity lubricating oils can
decrease engine life.
Oil flow through the engine

enters the suction tube and
travels into the gerotor-style
lubrication pump. The oil is
pressurized and fed into the oil
cooler cover. Within the cover a
pressure-regulating valve
regulates the oil to 414 kPa [60
psi]. Excess oil is returned to
the suction side of the
lubricating oil pump for 3.9L and
5.9L engines and to the oil pan
for 4.5L and 6.7L engines. Oil
continues through the
lubricating oil cooler to the
lubricating oil filter bypass
valve. The lubricating oil filter
bypass valve will open if the
pressure across the filter
exceeds 345 kPa [50 psi]. Oil
leaves the filter and supplies a
line to the turbocharger,
directed cooling nozzle rifle,
and main oil rifle through a
drilling between cylinders 1 and
2.
A main rifle runs the length of

the block on the fuel pump side
of the engine. The rifle supplies

lubricating oil to the main
bearings and crankshaft.
Lubricating oil flows from the
main bearings to the cam
journals/bushings and piston-
cooling nozzles, if equipped.
The drilling in the crankshaft
supplies lubricating oil to the
rod bearings. Vertical drillings
from the cylinder head deck to
the main oil rifle supply oil to the
cylinder head. Oil passes
through the cylinder head
gasket and enters the cylinder
head. The drilling continues in
the cylinder head to a drilling in
the rocker lever pedestal.
Internal drillings in the pedestal
supply lubricating oil to the
rocker shaft, push tube socket,
and crosshead pad. A second
main lubricating oil rifle runs the
length of the cylinder block on
the oil cooler side. This rifle
supplies lubricating oil to the
directed piston-cooling nozzles,
if equipped.
When the 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.
High lubricating oil pressure

occurs after the engine is first
started in cold weather. Cold-
start oil pressure typically will
be approximately 689 to 827

kPa [100 to 120 psi]. If the
pressure regulator plunger is
operating properly, the oil
pressure should drop back to
approximately 414 kPa [60 psi]
when normal operating
temperature is reached.
The engine will have high oil

pressure at normal operating
temperature if the lubricating
oil pressure regulator valve
sticks in the closed position.
Check the regulator for

freedom of movement. Refer
to Procedure Procedure 007-
029
Low lubricating 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:
Following a service
interval
At idle only
Operating on a steep
grade
Operating in rough sea.
High lubricating oil level can

cause low oil pressure. If the 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.
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.
A plugged lubricating oil 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 lubricating 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.
A steady decrease in oil

pressure over a long period can
be an indication of worn
bearings or excessive
lubricating oil pump wear.
Though similar in design and

appearance, there are many
variations of the lubricating
oil pump. Before installing a
new lubricating oil pump
make sure that the pump is
correct for you engine.
Refer to Procedure
Procedure 007-031 for
removal and installation
procedures. See Quickserve
Online to determine the
correct lubricating oil pump
part number.
CAUTION
Using diluted oil can cause

severe engine damage.
Check the condition of the

lubricating oil:
Thin, black oil is an

indication of fuel in the
oil
Milky discoloration is an
indication of coolant in
the oil.
Coolant in the oil can be caused

by:
Expansion plugs leaking

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 Procedure 007-
003
While operating, the oil

pressure will be higher than
coolant pressure. A leak in
the oil cooler will show as 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 into the oil.
If the oil cooler element

ruptures, the oil pressure will
force oil into the coolant
system.
Oil in the coolant should be

visible when the radiator cap
is removed. Refer to
003
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:
Rocker lever cover.

Refer to Procedure
Procedure 003-011.
Leaks indicate a
cracked cylinder head.
Lubricating oil drain
plug. Refer to
Procedure Procedure
007-037. Leaks
indicate defective oil
cooler, cylinder head
gasket, or cracked
cylinder head or block.
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. Refer to
Procedure 002-004
Inspect for cracks or any

other damage.
Fuel dilution of the lubricating

system is generally due to the
injector but may also be due to
internal damage to the high-
pressure pump.
Incomplete combustion in the

cylinders can result in unburned
fuel draining into the oil pan.
This condition can be caused

by a leaking injector or reduced
compression caused by
inadequate piston ring sealing.
An increase in white exhaust

smoke during the first start of
the day is a symptom that an
injector is leaking.
An injector leak will also

cause the engine to run
rough and have low power.
Remove and repair, or

replace leaking injectors.
Refer to Procedure
Procedure 006-026
The o-rings in the injectors

can be inspected for cracks
or wear. A missing or
damaged o-ring in an injector
can result in improper
disbursement of fuel into the
cylinder.
Also, a poor seal between

the injector and the high-
pressure transfer tube can
also cause the injector o-
rings to fail or leak into the
top of the cylinder head.
Inspect the injector o-ring.

Refer to Procedure 006-026
Various gaskets, seals, and

plugs are used to contain the
lubricating oil. Most leaks
can be identified during
routine inspections of the
engine and vehicle.
Worn or damaged seals in

the turbocharger can also
allow oil to leak into the
charge air cooler system and
be burned in the engine.
The condition can be verified

by removing the air
crossover tube or charge air
cooler tubing and looking for
oil. Refer to Procedure
Procedure 010-019 and
Refer to Procedure
Procedure 010-027
NOTE: If the engine

experiences a
turbocharger failure or any
other occasion where oil
or debris is put into the
charge air cooler, the
charge air cooler must be
cleaned.
Inadequate sealing of the

piston rings will result in oil
being blown out the breather
tube and/or consumed by
the engine. Refer to
010
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 gasket or cylinder head
gasket can allow oil to leak
into the coolant or coolant to
leak into the oil during a hot
shutdown.
Last Modified: 07-Mar-2013
Copyright © 2000-2010 Cummins Inc. All rights reserved.

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Lubricating Oil System - Overview Page 1 of 13

007-999 Lubricating Oil System - Overview

Cummins Inc. recommends the

NOTE: The SK designation is

NOTE: If CI/SK oils are not

Limited use of low-viscosity

Oil flow through the engine

A main rifle runs the length of

of the engine. The rifle supplies

When the diagnosing lubricating

High lubricating oil pressure

be approximately 689 to 827

The engine will have high oil

Check the regulator for

Low lubricating oil pressure (or

Operating in rough sea.

High lubricating oil level can

Low oil level will not normally

A plugged lubricating oil filter

Check the lubricating oil gauge

A loose lubricating oil suction

A steady decrease in oil

Though similar in design and

Using diluted oil can cause

Check the condition of the

Thin, black oil is an

Coolant in the oil can be caused

Expansion plugs leaking

Since the lubricating oil

While operating, the oil

If the oil cooler element

Oil in the coolant should be

To check for leaks,

Rocker lever cover.

Coolant in the lubricating oil

Remove the cylinder head

Inspect for cracks or any

Fuel dilution of the lubricating

Incomplete combustion in the

This condition can be caused

An increase in white exhaust

An injector leak will also

Remove and repair, or

The o-rings in the injectors

Also, a poor seal between

Inspect the injector o-ring.

Various gaskets, seals, and

Worn or damaged seals in

The condition can be verified

NOTE: If the engine

Inadequate sealing of the

Lubricating oil can also be

Also, a failed air compressor

Last Modified: 07-Mar-2013

Copyright © 2000-2010 Cummins Inc. All rights reserved.

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