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Oil Leakage & Consumption
Leak Locations: Underhood
| Under Engine
Oil Loss & Tests: Information
| Oil Consumption Test | Oil
Oil Leakage Locations
valve cover gaskets
intake manifold gaskets
cylinder head gaskets
engine front cover gasket
camshaft position sensor O-ring
oil level indicator tube connection
oil pressure sensor
oil bypass filter
oil pan gasket
oil pan front and/or oil pan rear seal
crankshaft front seal
crankshaft rear oil seal
Excessive Oil Loss and
The amount of oil an engine uses will vary with the way the vehicle
is driven in addition to normal engine-to-engine variation. This is especially
true during the first 16,100 km (10,000 miles) when a new engine is being
broken in or until certain internal engine components become conditioned.
Vehicles used in heavy-duty operation may use more oil. The following are
examples of heavy-duty operation:
Engines need oil to lubricate the following internal components:
severe loading applications
When the pistons move downward, a thin film of oil is left on the cylinder
walls. The oil is burned away on the firing stroke during combustion. If
an engine burned a drop of oil during each firing stroke, oil consumption
would be about one quart for every mile traveled. Fortunately, modern engines
use much less oil than this example. However, even efficient engines will
use some oil or they would quickly wear out. As the vehicle is operated,
some oil is also drawn into the combustion chambers past the intake and
exhaust valve stem seals and burned.
engine cylinder block cylinder walls
pistons and piston rings
intake and exhaust valve stems
intake and exhaust valve guides
all internal engine components
Many different conditions can affect oil consumption rates. The following
is a partial list of these items:
Operation under varying conditions can frequently be misleading. A vehicle
that has been run for several thousand miles on short trips or below-freezing
ambient temperatures may have consumed a "normal" amount of oil. However,
when checking the engine oil level, it may measure up to the full mark
on the oil level dipstick due to dilution (condensation and fuel) in the
engine crankcase. The vehicle then might be driven at high speeds on the
highway where the condensation and fuel boil off. The next time the engine
oil is checked, it may appear that a quart of oil was used in about 160
km (100 miles). This perceived 160 km (100 miles) per quart of oil consumption
rate causes customer concern even though the actual overall oil consumption
rate was about 2400 km (1500 miles) per quart.
operator driving habits
quality and viscosity of the oil
Make sure the selected engine oil meets the recommended API performance
category "SH" and SAE viscosity grade as shown in the vehicle Owner Guide.
It is also important that the engine oil is changed at the intervals specified
for the typical operating conditions.
Oil Consumption Test
The following diagnostic procedure is intended to be used to determine
the source of excessive internal oil consumption:
1. Note: Oil use is normally greater during the first 16,100 km (10,000
miles) of service. As mileage increases, oil use generally decreases. Vehicles
in normal service should get at least 1,450 km (900 miles) per quart after
16,100 km (10,000 miles) of service. High speed driving, towing, high ambient
temperature and other factors may result in greater oil use.
Define excessive oil consumption such as how many miles are driven per
quart of oil. Also determine owner's driving habits such as sustained high-speed
operation, towing, extended idle and other factors.
2. Verify engine has no external oil leak as described under «Engine
3. Verify engine has correct oil level dipstick.
4. Verify that the engine is NOT being run in an overfilled condition.
Check the oil level at least five minutes after a hot shutdown with the
vehicle parked on a level surface. The oil level should never be above
the top of cross-hatch area and "F" in FULL. If significantly overfilled,
perform Steps 5a through 5d.
5. Perform an oil consumption test:
a. Drain engine oil. Replace oil bypass filter and refill with one
quart less than recommended.
b. Run the engine for three minutes (10 minutes if cold) and allow
oil to drain back for at least five minutes with vehicle on level surface.
c. Remove engine oil level dipstick and wipe clean. (Do not wipe with
anything contaminated with silicone compounds.) Reinstall oil level dipstick
and seat the oil level dipstick firmly in the oil level indicator tube.
Remove the oil level dipstick and draw a mark on the back (unmarked) surface
at the indicated oil level. (This level should be about the same as the
ADD mark on the face of the oil level dipstick.)
d. Add one quart of oil. Restart the engine and allow to idle for at
least two minutes. Shut off the engine and allow oil to drain back for
at least five minutes. Mark the oil level dipstick using the procedure
above. (This level may range from slightly below the top of the cross-hatched
area to slightly below the letter "F" in FULL.)
e. Record vehicle's mileage.
f. Instruct the owner to drive the vehicle as usual and:
(1) Check the oil level regularly at intervals of 160-240 km (100-150
(2) Return to the service point when the oil level drops below the
lower ADD mark on the oil level dipstick.
(3) Add only full quarts of the same oil in an emergency and note the
mileage at which the oil is added.
g. Check the oil level under the same conditions and at the same location
as in Steps c and d.
6. Check PCV valve system. Make sure system is not plugged.
(1) Measure the distance from the oil level to the UPPER mark on theoil
level dipstick and record.
h. If the oil consumption rate is unacceptable, go to Step 6.
(2) Measure the distance between the two marks and record.
(3) Divide the first measurement by the second.
(4) Divide the distance driven during the oil test by the result. This
quantity is the approximate oil consumption rate in kilometers per liter
(KPL) or miles per quart (MPQ).
7. Check for plugged oil drain-back holes in cylinder heads and cylinder
8. If the condition still exists after performing the above tests, go
to Step 9.
9. Perform a Compression Test (below), and/or an Oil Leak and Valve
Guide Seal Test as described, with Rotunda Pressurization Kit 014-00705
or equivalent. This can help to determine the source of oil consumption
such as valves, piston rings or other areas.
10. Note: After checking for worn parts, determine which parts should
be replaced. Use correct parts. Check valve guides for excessive guide
clearance. Replace all valve stem seals after verifying valve guide clearance.
11. Worn or damaged internal engine components can cause excessive oil
consumption. Small deposits of oil on tip of spark plugs can be a clue
to internal oil consumption. If internal oil consumption still persists,
proceed as follows:
a. Remove engine from vehicle and place it on Rotunda Engine Stand
014-00232 or equivalent. Remove intake manifolds, cylinder heads, oil pan
and oil pump.
12. Perform oil consumption test as described to confirm oil consumption
concern has been resolved.
b. Check piston ring clearance, ring gap and ring orientation. Service
c. Check for excessive bearing clearance. Service as required.
Oil Pressure Test
SPECIAL SERVICE TOOL(S) REQUIRED
1. Disconnect and remove the oil pressure sensor from the engine.
|Engine Oil Pressure Gauge
2. Connect an Engine Oil Pressure Gauge T73L-6600-A and Transmission
Test Adapter D87C-77000-A or equivalent to the oil pressure sender oil
3. Run the engine until normal operating temperature is reached.
4. Run the engine at 3,000 rpm and record the gauge reading.
5. The oil pressure should be:
6. If the pressure is not within specification, check the following possible
276-414 kPa (40-60 psi) at 3,000 rpm
a. insufficient oil
b. oil leakage
c. worn or damaged oil pump
d. oil pump screen cover and tube
e. excessive main bearing clearance
f. excessive connecting rod bearing clearance
g. excessive camshaft bearing clearance