Crankcase, 3.8L. Porsche 993  ❭  99310100541

• Porsche 964 (911) C2 1989-93
• Porsche 964 (911) C4 1989-93
• Porsche 964 (911) RS 3.6L 1991-93
• Porsche 964 (911) RS 3.8L 1991-93
• Porsche 964 (911) TURBO 3.3L 1991-93
• Porsche 964 (911) TURBO 3.6L 1991-93
• Porsche 993 (911) C2 1994-97
• Porsche 993 (911) C4 1994-97
• Porsche 993 (911) RS 1994-97
• Porsche 993 (911) C2S 1994-97
• Porsche 993 (911) C4S 1994-97
• Porsche 993 (911) TURBO 1994-96
• Porsche 993 (911) GT2 1994-97
• Porsche 993 (911) TURBO S 1994-97
• Porsche 996 TURBO 2000-05
• Porsche 996 GT2 2001-05
• Porsche 996 GT3 MKI 1999-02
• Porsche 924S 2.5L 1986-87
• Porsche 924S 2.5L 1988
• Porsche 944 2.5L 8V 1982-87
• Porsche 944 2.7L 8V 1988-89
• Porsche 944S 2.5L 16V 1987-88
• Porsche 944S2 3.0L 16V 1989-91
• Porsche 944 Turbo 2.5L 8V 1985-88
• Porsche 944 Turbo 2.5L 8V 1989-91
• Porsche 944 Turbo S 2.5L 8V 1988
• Porsche 968 3.0L 1992-94
• Porsche 968 Sport 3.0L 1994-95
• Porsche 968 CS 3.0L 1993-95
• Porsche 968 Turbo S 3.0L 1993-94
• Porsche 928 4.5L 1978-82
• Porsche 928S 4.7L 1981-83
• Porsche 928S2 4.7L 1984-86
• Porsche 928S4 5.0L 1987-92
• Porsche 928GT 5.0L 1989-91
• Porsche 928GTS 5.4L 1992-95

The rear main oil seal, often referred to as the RMS (Rear Main Seal), is one of the most important sealing components in the engine. It retains engine oil inside the crankcase while allowing the crankshaft to rotate at high speed. A worn or damaged seal can lead to oil leaks, clutch contamination and unnecessary engine maintenance costs if left unattended.

This OE Match replacement provides the correct fit, sealing performance and durability required for maintenance, engine rebuilds and preventative servicing.

What Does the Rear Main Oil Seal Do?

The rear main oil seal forms a seal around the rear section of the crankshaft.

Its primary functions include:

• Preventing engine oil leaks
• Sealing the rear crankshaft opening
• Protecting the flywheel area from contamination
• Maintaining correct engine oil levels
• Preventing oil reaching the clutch assembly
• Supporting long-term engine reliability
• Allowing smooth crankshaft rotation

Without a properly functioning rear main seal, oil can escape from the engine and create a range of reliability issues.

Why Do Rear Main Oil Seals Fail?

Like all rubber sealing components, rear main oil seals are subject to wear and ageing.

Common causes of failure include:

• Heat cycling
• Age-related hardening
• Crankshaft wear
• Engine vibration
• Long-term oil exposure
• Improper installation
• Excessive crankcase pressure
• High mileage use

Over time, the sealing lip can lose flexibility and its ability to maintain consistent contact with the crankshaft surface.

Symptoms of a Failing Rear Main Oil Seal

Common warning signs include:

• Oil leaks between engine and gearbox
• Oil drips beneath the vehicle
• Oil contamination around the flywheel housing
• Clutch slip caused by oil contamination
• Burning oil smell
• Gradual oil level loss
• Oil residue on transmission bellhousing

Because the seal is located behind the flywheel, leaks can often be mistaken for other engine oil leaks unless properly diagnosed.

When Should the Rear Main Oil Seal Be Replaced?

Replacement is recommended when:

• Oil leakage is present
• The gearbox is being removed
• Replacing the clutch assembly
• Rebuilding the engine
• Refurbishing the crankshaft
• Carrying out preventative maintenance
• The original seal shows signs of ageing
• Engine mileage is high

Many Porsche specialists recommend replacing the rear main seal whenever the clutch or flywheel is removed, as labour access is significantly easier during these procedures.

Why Replacement Matters

A leaking rear main oil seal can lead to far more expensive repairs if ignored.

Benefits of replacement include:

• Prevention of engine oil leaks
• Protection of the clutch assembly
• Improved engine cleanliness
• Reduced maintenance costs
• Improved reliability
• Professional rebuild standards
• Long-term sealing performance
• Greater peace of mind

Replacing the seal during clutch or engine work is considered a smart preventative maintenance measure.

A magnetic sump oil drain plug is a type of oil drain plug that contains a small magnet designed to attract and capture metallic particles that may be present in your engine's oil. While this type of drain plug is not exclusive to Porsche and can be used in various vehicles, it can provide several benefits, including:

Improved Engine Longevity: The magnet in the drain plug helps to capture tiny metal particles, such as iron, steel, or aluminum, that may circulate in the engine oil. Removing these particles can reduce wear and tear on engine components, potentially extending the engine's lifespan.

Enhanced Engine Performance: By reducing the presence of contaminants in the oil, a magnetic drain plug can help maintain the oil's lubricating properties, which is crucial for smooth engine operation. Clean oil can also contribute to improved fuel efficiency.

Early Detection of Problems: As the magnetic drain plug collects metallic debris, it can serve as an early warning system. By inspecting the drain plug during oil changes, you can get an idea of the engine's condition and detect any unusual wear or damage before it becomes a major issue.

Reduced Maintenance Costs: Regularly inspecting and cleaning a magnetic drain plug can prevent larger issues from developing over time. Addressing potential problems early can save you money on more extensive repairs down the road.

Peace of Mind: Knowing that you are taking steps to protect your engine from premature wear and tear can give you peace of mind as a vehicle owner. It's a relatively inexpensive and simple modification that can provide added assurance.

Easy Installation: Magnetic drain plugs are typically straightforward to install. They often replace the existing drain plug and require no special tools or modifications.

While magnetic drain plugs can offer these benefits, it's essential to remember that they are not a substitute for regular oil changes and proper maintenance. Regular oil changes with the appropriate oil and filter are still crucial for the health and longevity of your engine. Additionally, magnetic drain plugs may not capture all types of contaminants, so they should be seen as a supplementary measure rather than a comprehensive solution.