The rear main seal (RMS) on the Porsche 986 Boxster is a common wear item that can cause oil leaks and driveability concerns. Understanding the part, its symptoms, and replacement options is essential for any owner or prospective buyer. This guide covers everything you need to know about the 986 Porsche RMS part, including part numbers, costs, and whether to choose OEM or aftermarket.
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Engine Air/Oil Separator for Porsche Boxster 986 (1997-2002)
What Is the Rear Main Seal on a Porsche 986?
The rear main seal is a circular seal located between the engine and the transmission. It prevents engine oil from leaking out where the crankshaft exits the engine block. On the Porsche 986, which uses the M96 flat-six engine, the RMS is a known weak point, especially in early models (1997–1999) and higher-mileage cars.
Design and Location
The RMS sits at the back of the engine, behind the flywheel. It consists of a metal outer ring and a PTFE or rubber lip that contacts the crankshaft. The seal is pressed into the engine housing and must be replaced when it fails. The repair requires removing the transmission and flywheel, making it labor-intensive.
Common Symptoms of a Failing RMS
A failing rear main seal typically presents with visual and olfactory clues. Ignoring these symptoms can lead to more serious engine damage.
Oil Leaks
The most obvious sign is oil dripping from the bell housing area between the engine and transmission. You may notice spots on the ground or oil residue on the underside of the car. Unlike a valve cover gasket leak, an RMS leak tends to appear as a slow, steady weep.
Burning Oil Smell
Oil that drips onto the exhaust system will burn off, creating a distinct smell inside the cabin. If you smell burning oil after driving, especially when stopped, the RMS is a likely culprit.
Low Oil Level and Pressure
A persistent RMS leak will cause the oil level to drop over time. If the leak is significant, you may see low oil pressure warnings on the dash. This can lead to engine starvation if not addressed promptly.
OEM vs Aftermarket RMS Parts for the 986
When replacing the RMS, you have several options. The original Porsche part is generally recommended for longevity, but quality aftermarket alternatives exist.
Porsche OEM Part Numbers
The factory RMS for the 986 Boxster (2.5L and 2.7L engines) is part number 999-113-329-50. This is a complete seal assembly with an integrated dust lip. For later models (2.7L and 3.2L), the updated part 999-113-329-52 is often used. Always verify fitment with your car’s VIN.
Aftermarket Options
Reputable aftermarket suppliers include INA and Febi Bilstein. These brands produce seals that meet or exceed OEM specs at a lower price. For example, INA part 561 3000 10 is a direct replacement. Some enthusiasts also recommend the Elring brand. Avoid generic no-name seals, as premature failure is common.
Key consideration: Some aftermarket seals use a different material (e.g., viton) that may resist heat better than the OEM PTFE. However, the installation process is identical.
RMS Replacement Cost and Considerations
Replacing the RMS is not a simple DIY for most owners. The labor involved drives up the cost significantly.
Labor and Parts
A professional replacement typically costs $800 to $1,200 at an independent Porsche specialist. This includes parts, labor (4–6 hours), and sometimes new sealant. The RMS part itself is only $30 to $80 for OEM or quality aftermarket. Dealerships may charge $1,500 or more.
DIY vs Professional
If you have mechanical experience and a lift or jack stands, replacing the RMS is possible. The hardest part is removing and reinstalling the transmission. You will need special tools like a flywheel holder and potentially an alignment tool. Many owners opt to combine the RMS replacement with the IMS bearing (if applicable) or clutch replacement, as the transmission is already out.
Practical Recommendation
For most 986 owners, choosing an OEM Porsche RMS (part 999-113-329-50 or 999-113-329-52) is the safest bet. If you are experienced and want to save money, a quality aftermarket seal from INA or Febi is acceptable. Always inspect the flywheel and pilot bearing while the transmission is removed. Do not reuse the old seal if the surface is worn. Budget for the repair and address it promptly to avoid secondary damage.
In summary, the 986 Porsche RMS part is a maintenance item that should not be ignored. Early detection of leaks and timely replacement will keep your Boxster running reliably.