2021 Mercedes-Benz AMG GT Oil Leak from Rear Main Seal

Owners of 2021 Mercedes-Benz AMG GT vehicles, specifically those with M17x engine variants, may experience issues related to oil leaks. Mercedes-Benz has released Technical Service Bulletin (TSB) LI01.40-P-079518, dated July 16, 2025, to address customer complaints regarding oil use, oil leaking, or an oil smell coming from the engine area.

Symptoms

If you own a 2021 Mercedes-Benz AMG GT, you might notice one or more of the following symptoms indicating a potential oil leak:

• Oil use: The engine consumes oil at an unusual rate.
• Oil leaking: Visible oil spots on the ground or around the rear of the engine and at the engine/transmission interface.
• Oil smell: A distinct burning oil smell, especially after driving.
• External oil loss: This issue is technically categorized under "Power generation > Engine lubrication/oil cooling > Leakage > External oil loss" within Mercedes-Benz's diagnostic system.

Cause of the Oil Leak

The root cause of the Mercedes-Benz AMG GT oil leak is identified as oil escaping from the rear main seal and/or the rear main seal plate. These components are critical for sealing the rear of the engine block, specifically within function group 01.40, which covers the crankcase, timing case cover, and end cover.

Diagnosis Procedure

Technicians should follow a precise procedure to confirm the leak location:

1. Initial Inspection: Carefully inspect the rear main seal for any signs of damage such as being sucked in, rolled, or cut. Reference images like "Rolled Seal.jpg" and "Rolled Seal 2.jpg" from the bulletin can help identify these conditions.
2. Leak Confirmation: To pinpoint the exact source, thoroughly clean the suspected area around the rear main seal and/or rear main seal plate. Apply trace powder to the cleaned surface.
3. Vehicle Operation: Run the vehicle on a lift or at low speed in a controlled environment to observe the trace powder. It is crucial do not attempt at high speed or in wet areas as this will make the results difficult to assess.

Repair Procedure Summary

The repair process depends on the confirmed leak source:

1. Previous Replacement Check: If the rear main seal plate has been replaced previously according to this bulletin's instructions, a TIPS case must be opened before proceeding with further repairs.
2. Seal-Only Leak: If the leak is confirmed to be emanating solely from the seal, replace both air/oil separators. Afterward, completely clean the bellhousing area and re-test with trace powder. If the leak does not reappear, the vehicle can be released.
3. Seal Plate and Seal Leak: If the leak persists after replacing the air/oil separators, or if the leak is initially confirmed to be from the rear main seal plate, the rear main seal plate and rear main seal must be replaced. This involves pulling the rear main seal plate, thoroughly cleaning the block mating surface, and then installing the new rear main seal plate and rear main seal.
4. Sealant Application: When installing, apply sealant directly to the engine BLOCK instead of the plate to ensure proper coverage. The sealant path must be followed exactly as depicted in the "RMS Sealant Path.png" drawing provided in the bulletin.
5. Post-Installation: After installation, lubricate a feeler gauge with oil and run it between the new rear main seal and the crankshaft. This step helps clear any small debris and prevents binding or stiction.

Required Parts

To address the Mercedes-Benz AMG GT oil leak, the following parts may be required:

• Crankcase Cover: Part number A1770103708 (Quantity: 1). Note: Technicians must remove CLAMPING SLEEVE (Cap to cylinder crankcase) part number A 601 992 01 25 before installing the new crankcase cover.
• Screws: Part number N000000 001144 (Quantity: 13).

Important Warnings for Technicians

• If the rear main seal plate has been previously replaced per the instructions in this bulletin, technicians must open a TIPS case before proceeding with further diagnosis or repair.
• During the diagnostic phase, when running the vehicle to observe trace powder, technicians do not attempt at high speed or in wet areas as this will make the results difficult to assess.

Source: NHTSA ID: 10255866