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Oil Separators & Vent lines
Fits: Porsche Boxster 986 2.5L M96.20
The AOS is basically a small diaphragm distillery which distills the minute amounts of oil mist in the crankcase, liquifies it and sends it back to the crankcase. The "clean" air is now sent into the air intake (after the throttle body) to be burned off by the engine.
When the AOS starts to fail it cannot separate all of the oil out of the mist and some liquid oil is sent to the air intake.
A few drops of oil is enough to generate the GREAT SMOKE BOMB for which our cars are famous for.
A big smoke bomb once in a while is completely normal, due to the architecture of the flat-6 engine, which may let a drop of oil flow into one of the combustion chambers sporadically.
Click 'Zoom in' for large parts diagram.
Diagram Ref No 1, 4, 5, 10
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
OILSEPARATOR.986.1.OEM
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
The AOS is basically a small diaphragm distillery which distills the minute amounts of oil mist in the crankcase, liquifies it and sends it back to the crankcase. The "clean" air is now sent into the air intake (after the throttle body) to be burned off by the engine.
When the AOS starts to fail it cannot separate all of the oil out of the mist and some liquid oil is sent to the air intake.
A few drops of oil is enough to generate the GREAT SMOKE BOMB for which our cars are famous for.
A big smoke bomb once in a while is completely normal, due to the architecture of the flat-6 engine, which may let a drop of oil flow into one of the combustion chambers sporadically.
Fits:
Porsche Boxster 986 1997-02
Click 'Zoom in' for large parts diagram.
Diagram Ref No 1.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610702304
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
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AOS Oil / Air Separator
Keep your Porsche Boxster 986 running smoothly with this OE
Match Air Oil Separator (AOS). Designed for 1997-2002 Porsche
Boxster 986 models equipped with the M96 flat-six engine, the Air Oil Separator
is a vital component of the engine's crankcase ventilation system.
Fits:
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
Diagram Ref No 1
During normal operation, combustion gases and oil vapours accumulate within the engine crankcase. The Air Oil Separator separates oil particles from these gases, returning the oil to the engine while directing cleaned vapours back into the intake system for combustion. This process helps maintain engine efficiency, reduce emissions and prevent excessive oil contamination within the intake tract.
The Air Oil Separator is one of the most recognised maintenance items on Porsche M96 engines. As the internal diaphragm ages, the separator can lose its ability to regulate crankcase pressure correctly, resulting in a variety of performance and drivability issues.
Manufactured to OE Match standards, this replacement unit restores proper crankcase ventilation and helps maintain the performance and reliability expected from your Porsche Boxster.
What Does the Air Oil Separator Do?
The Air Oil Separator forms part of the Positive Crankcase Ventilation (PCV) system.
Its primary functions include:
- Separating oil from crankcase gases
- Returning oil back into the engine
- Regulating crankcase vacuum
- Reducing oil consumption
- Supporting emissions control systems
- Maintaining engine efficiency
- Preventing excessive oil contamination of the intake system
A correctly functioning AOS helps the engine breathe properly while minimising oil carryover into the intake manifold.
Why Do Air Oil Separators Fail?
The internal diaphragm and valve assembly are constantly exposed to engine heat, oil vapours and vacuum pressure.
Common causes of failure include:
Diaphragm deterioration Heat cycling Age-related wear Oil contamination Internal valve failure High mileage Crankcase pressure fluctuations Long-term exposure to engine vapoursOver time, the separator loses its ability to maintain the correct crankcase vacuum levels.
Symptoms of a Failing AOS
The Porsche Boxster Air Oil Separator often provides several warning signs before complete failure.
Common symptoms include:
- Excessive white smoke from the exhaust
- Increased oil consumption
- Rough or unstable idle
- Whistling noises from the engine
- Vacuum leaks
- Check engine warning light
- Oil contamination within the intake system
- Excessive crankcase vacuum
- Difficulty removing the oil filler cap with the engine running
These symptoms typically indicate the separator is no longer functioning correctly.
When Should the AOS Be Replaced?
Replacement should be considered when any of the above symptoms are present.
The AOS is also commonly replaced during:
- High-mileage maintenance
- Engine rebuilds
- Intake system servicing
- Preventative maintenance schedules
- Crankcase ventilation system repairs
Many Porsche specialists recommend replacing the AOS before complete failure to avoid more serious drivability concerns.
Why Replacement Matters
A failed Air Oil Separator can significantly affect engine performance and reliability.
Benefits of replacement include:
- Reduced exhaust smoke
- Improved idle quality
- Lower oil consumption
- Correct crankcase pressure regulation
- Improved engine efficiency
- Reduced intake contamination
- Enhanced reliability
- Restoration of factory engine performance
Replacing the separator early helps prevent secondary issues and maintains the health of the M96 engine.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610702304
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche Boxster 986 >>2002
Porsche 996 Carrera M >> 663 09950 Cyl 4-6
Click 'Zoom in' for large parts diagram.
Diagram ref no 6
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610704751
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche Boxster 986 >>2002
Porsche 996 Carrera M >> 663 09950 Cyl 4-6
Click 'Zoom in' for large parts diagram.
Diagram Ref No 4
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610714755
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
Shop Securely
12 Month Warranty
Worldwide Delivery
Fits:
Porsche Boxster 986 >>2002
Porsche 996 Carrera M >> 663 09950 Cyl 4-6
Click 'Zoom in' for large parts diagram.
Diagram Ref No 4
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610714755
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche 986 Boxster 1997-04
Porsche 987.1 Boxster 2005-08
Porsche 987C.1 Cayman 2005-08
Porsche 996 Carrera 3.4L / 3.6L 1998-05
Porsche 997.1 Carrera 3.6L / 3.8L 2005-08
Click 'Zoom in' for large parts diagram.
Diagram ref no 20
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610124151
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche Boxster 987 2.7L 2005-08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
- Porsche Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
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12 Month Warranty
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Fits:
Porsche 911 - 1978 to 1989
Porsche 964 - 1989 to 1994
Porsche 993 - 1994 to 1998
Porsche 986 Boxster - 1997 to 2004
Porsche 996 - 1997 to 2005
Porsche 997.1 - 2005 to 2008
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99951255400
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- 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 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
- Porsche 996 TURBO 2000-05
- Porsche 996 GT2 2001-05
- Porsche 996 GT3 MKI 1999-02
- Porsche 996 GT3 MKII 2003>>
- Porsche 996 GT3 RS 2003-04
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
- Porsche 997 MK1 TURBO 2007-09
- Porsche 997 MK1 GT3 / GT3 RS 2007-09
- Porsche 997 MK1 GT2 2007-09
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche 986 Boxster 1997-2004
Porsche 996 Carrera 1998-2004
Diagram Ref No 11
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99951255101
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche 986 Boxster 1997-04
Porsche 996 C2 / C4 3.4L 1998-01
Click pictrue for large parts diagram.
Diagram Ref No 9.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99951263000
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
Shop Securely
12 Month Warranty
Worldwide Delivery
Fits:
Porsche 986 Boxster - 1997 to 2004
Porsche 996 C2 / C4 3.4ltr - 1998 to 2001
Click 'Zoom in' for large parts diagram.
Diagram ref no 9
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99951263000
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
Shop Securely
12 Month Warranty
Worldwide Delivery
Fits:
Porsche 996 1998-02 3.4L
Porsche Boxster 986
Click 'Zoom in' for large parts diagram.
Diagram Ref No 10.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610723752
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
Shop Securely
12 Month Warranty
Worldwide Delivery
Fits:
Porsche 996 1998-02 3.4L
Porsche Boxster 986
Click 'Zoom in' for large parts diagram.
Diagram Ref No 10.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610723752
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche Boxster 986 2.5L 1999
Vehicles with chassis numbers from 65X01420
Diagram Ref No 5.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610714506
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche Boxster 986 2.5L 1999
Vehicles with chassis numbers from 65X01420
Diagram Ref No 5.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610714506
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
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12 Month Warranty
Worldwide Delivery
Fits:
Porsche Boxster 986 2.5L 1997>>1999
Vehicles with chassis numbers upto 65X01419
Diagram Ref No 5
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610714505
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
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12 Month Warranty
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Oil Separators & Vent Lines – Maintain Clean Airflow and Engine Efficiency
The oil separator and vent line system plays a critical role in your Porsche’s crankcase ventilation process. By separating oil vapour from the engine’s blow-by gases, these components ensure only clean air is returned to the intake system — reducing emissions, preventing carbon build-up, and maintaining consistent engine performance.
At Design911, we stock a complete range of oil separators, breather hoses, and vent lines designed for Porsche engines of all generations. Manufactured from high-grade, heat- and oil-resistant materials, these components are built to handle the demands of high-performance driving, ensuring a tight seal, proper ventilation, and long-lasting reliability.
Whether you’re maintaining a daily-driven 911 or servicing a track-ready Cayman, our oil separators and vent lines help preserve your engine’s efficiency, longevity, and power output.
What Do Oil Separators & Vent Lines Do?
The oil separator and vent system controls crankcase pressure and removes oil vapour from the air circulating inside the engine.
Core Functions:
- Separate oil vapour from crankcase gases, keeping intake air clean.
- Prevent oil from entering the intake manifold or combustion chamber.
- Maintain stable crankcase pressure for efficient engine breathing.
- Reduce harmful emissions and extend engine life.
- Support consistent power delivery and smooth idle performance.
By ensuring clean ventilation and stable pressure, these components protect your Porsche’s engine from oil contamination and performance loss.
Why Do Oil Separators & Vent Lines Fail?
Over time, heat cycles, oil vapours, and pressure fluctuations cause these parts to degrade or clog, leading to poor ventilation and increased oil consumption.
- Common Causes of Failure Include:
- Clogged internal membranes in the separator.
- Cracked or brittle vent lines from heat and age.
- Oil leaks from worn seals or connections.
- Vacuum leaks, causing rough idling or poor throttle response.
- Build-up of sludge or condensation within breather hoses.
Typical symptoms include increased oil consumption, blue exhaust smoke, rough idle, or oil leaks around the intake area, all indicating the need for inspection or replacement.
Why Replace Components?
Replacing a faulty oil separator or vent line restores proper crankcase ventilation and prevents costly engine issues like carbon build-up or oil contamination. Our precision-engineered replacements are designed for accurate fitment and long-term durability, ensuring your Porsche operates efficiently.
Key Benefits:
- Restores clean airflow and stable crankcase pressure.
- Reduces oil leaks and smoke from the exhaust.
- Improves fuel efficiency and throttle response.
- Constructed from high-quality, heat- and oil-resistant materials.
- Direct-fit compatibility with Porsche engines.
- Ideal for maintenance, rebuilds, or performance tuning.
Upgrading or replacing your oil separator and vent lines is essential for maintaining your Porsche’s smooth performance and clean emissions system.
Highlights:
- High-quality Porsche oil separators, breather hoses, and vent lines.
- Ensures clean crankcase ventilation and stable engine pressure.
- Reduces oil leaks, smoke, and carbon build-up.
- Durable construction for long-term reliability.
- Direct-fit for Porsche 911, Cayman, Boxster, Panamera & more.
- Perfect for preventive maintenance or full engine rebuilds.
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