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DIAGNOSTIC SHEET MAS002116 ‐ N° 002.2020
Problem: Oil leaks in the gearbox or Bell housing area‘s
Models: All Models Sedans and SUV
References from BOL reports:
Oil leaks from the gearbox ‐ All Wheel Drive Transfer Case Engine oil leaks from the crankshaft rear main seal , engine block
threaded plug Gearbox oil leaks from the gearbox
Oil traces can be found close to the gearbox oil pan possibly from the oil pan fixing screws, or area’s above, leaking down to the gearbox oil pan. (Figure 1).
Figure 1
Conditions: No particular conditions.
DTCs in ECUs: No DTCs in any ECU.
Troubleshooting: Case 1: Lift the Vehicle on a hoist and check whether there is oil leaking in the connection area of the pipes at the gearbox and at the WTOC (Water Transmission Oil Cooler, engine coolant‐gearbox oil heat exchanger), as shown in Figure‘s 2 and 3.
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Figure 2: Section 03.50‐2 of the Spare Parts Catalogue.
Inspect for possible leaks at the connections of the pipes to the gearbox, as shown in Figure 3.
Figure 3
Inspect the WTOC (Water Transmission Oil Cooler, engine coolant‐gearbox oil heat exchanger) as shown below in Figure 4.
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Figure 4
A BOL must be opened prior to removal of any parts (components).
If oil leaks are found in the junction of the pipes with the gearbox or in the WTOC, proceed with removing the two pipes from the gearbox and perform a bubble test in the following way:
1. Fill a bucket or a basin with water.2. Immerse the pipe in the water and completely obstruct one end with your
finger.3. Insert the tip of a compressed air gun in the open end of the pipe and
gently pressurize the pipe.4. If air bubbles escape to the water, this means that the pipe has internal
damage and must be replaced.5. If air bubbles do NOT appear in the water, gently, flex the pipe in order to
replicate the fitting of the pipe in the vehicle, repeating steps 2 and 3.6. If air bubbles still do NOT appear in the water, replace the WTOC and the
relevant pipes. Prepare the parts for shipping through parts return for furtheranalyses.
7. Clean any oil residue and perform a road test to verify the problem wassolved.
Case 2: 1. Verify the gearbox oil level.
If the gearbox oil level is low, restore the level to the requiredspecifications and make note of the amount of oil added .If the gearbox oil level is compliant to specifications, this means that theleak doesn’t come from the gearbox.
2. Carefully clean and dry all the areas where talcum or trace powder isgoing to be applied, in particular the area where the leak is.
3. Perform a road test making the oil reach the operating temperaturein order to point out the potential source of the leak.
4. Check again whether there is any leaks.5. Potential areas of leaks are as follows:
Case 5.1: Interface at the gearbox‐gearbox oil pan.Case 5.2: Interface between the engine – gearbox. (BellHousing)Case 5.3: Interface between the gearbox – AWD transfer caseCase 5.4: Rear‐end of the gearbox housing (RWD version)
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In Case 5.1., The gearbox oil pan kit must NOT be replaced unless it shows
physical damage from ouside influences. (Bottoming out, etc.)
In Case 5.2, (Interface between the engine – gearbox) as shown in Figure 5,
proceed as described in steps 5.2.1 to 5.2.4 listed below.
Figure 5
5.2.1. Clean the area affected by the leak.
5.2.2. Verify with an endoscope, whether there is any oil accumulation
between the engine and gearbox inside the bell housing.
5.2.3. If there is oil accumulation, attach pic’s to the BOL. Remove the
gearbox according to Workshop Manual procedures and verify the
correct sealing of the crankshaft rear seal ring as shown in Figure
6 and Figure 7.
5.2.4. When performing the check, make sure there is no oil leaking from
the threaded oil plug on the engine block shown in the upper
portion of Figure 6.
Figure 6
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Figure 7
If the area mentioned in steps 5.2.3 and 5.2.4 (rear main seal or threaded oil plug) shows leaks, repair as per the Workshop Manual instructions only after having received authorization through a BOL report. In case 5.3 (leaks between the gearbox – AWD transfer case) as shown in Figure 8, submit a BOL report as a Support Request.
Figure 8 In case 5.4: Replace the gearbox output shaft seal ring, as shown in Figure 9,
following the Workshop Manual. Perform a road test to ensure the problem is
resolved.
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Figure 9
NOTES:
Attach pictures and/or videos to the Blue On Line report. Concerning a leak from the oil heat exchanger pipes, it is requested to perform a bubble test, immersing and flexing the pipes in water, blowing in compressed air into the pipe. It is recommended to bend/flex the pipe in both directions, even by a small amount, because if a cut is on the inner side of PTFE (Polytetrafluoroethylen)‐pipe, it will become more evident by flexing the pipe.
This can give a clear indication that the leak comes from the pipes. If residue is in the gearbox oil pan area as well as from its fitting screws to the gearbox housing, it could be misleading giving the impression that a leak comes from the pan itself, as shown in Figure 10. This wrong impression is a consequence of the fact that the leak could accumulate in the surface between the screw head and the oil pan itself, as highlighted in Figure 11. This leak could be coming from other areas in the upper end of the engine (the WTOC, Valve cover, etc.) Should there be oil accumulation in the gearbox oil pan area, it is suggested to:
1. Remove the fixing screws (one at a time) from the oil pan to the gearbox. 2. Clean the screws and the mounting surface on the oil pan mounting area. 3. Torque the screws into the gearbox oil pan.
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Figure 10: Leaks in the gearbox oil sump screw area after cleaning, application of talcum and road test.
Figure 11: Engine oil accumulation in the seat of the gearbox oil sump fixing screw.
In the event the problem is not resolved, submit a BOL report as a Support Request.
