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- Porsche 957 Cayenne Turbo / Turbo S 4.8L 2007-10
The Air / Oil Separator to Crankcase Vent Line is a OE MATCH engine ventilation component designed to connect the air/oil separator (AOS) to the crankcase ventilation system. This line allows separated crankcase gases to be routed correctly back into the intake system while helping prevent oil vapour from entering critical engine components.
Fits:
- Porsche 957 Cayenne Turbo / Turbo S 4.8L 2007-10
Diagram Ref No 1
What This Product Does:
- Routing crankcase gases from the air/oil separator
- Supporting efficient oil vapour separation
- Maintaining proper crankcase pressure regulation
- Reducing oil contamination in the intake system
- Helping prevent sludge build-up inside the engine
Symptoms Of Wear Or Failure:
- Rough idle or unstable engine performance
- Check Engine Light illumination
- Increased oil consumption
- Oil leaks from seals or gaskets
- Whistling or hissing noises (vacuum leak)
- Excessive smoke from the exhaust
- Oil residue around breather or intake components
Why Replacement Matters:
- Restore correct PCV system operation
- Prevent oil leaks and pressure-related damage
- Improve engine performance and efficiency
- Protect intake components from oil contamination
- Avoid costly engine repairs
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
94810722951
The product you are viewing cross references to these numbers
- 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 Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
AOS Oil / Air Separator
Maintain the performance and reliability of your Porsche
Boxster 986 with this OE Match Oil / Air Separator (AOS). A
critical component of the M96 engine crankcase ventilation system, the Air Oil
Separator helps separate oil vapour from crankcase gases before they are
returned to the engine intake system.
Fits:
- 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 Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
Diagram ref no 1
During normal engine operation, pressure builds inside the crankcase and oil vapour becomes suspended within the circulating gases. The AOS removes this oil mist, allowing the oil to return to the engine while directing cleaned gases back into the intake system for emissions control and efficient combustion.
The Air Oil Separator is a well-known service item on Porsche M96 engines. As the internal diaphragm ages and deteriorates, the separator can lose its ability to regulate crankcase vacuum correctly, leading to a variety of drivability and engine performance issues.
Manufactured to OE Match specifications, this replacement unit provides the correct fitment and performance needed to restore proper crankcase ventilation and engine operation.
What Does the Oil / Air Separator Do?
The AOS forms part of the Positive Crankcase Ventilation (PCV) system and performs several important functions.
Its primary roles include:
- Separating oil from crankcase vapours
- Returning oil to the engine
- Regulating crankcase vacuum
- Reducing oil consumption
- Supporting emissions control
- Maintaining engine efficiency
- Preventing excessive oil contamination of the intake system
Without a functioning AOS, excess oil can be drawn into the intake system and combustion chambers.
Why Do Air Oil Separators Fail?
The Air Oil Separator contains an internal diaphragm and valve assembly that is constantly exposed to heat, vacuum and engine oil vapours.
Common causes of failure include:
- Diaphragm deterioration
- Age-related wear
- Heat cycling
- Oil contamination
- Internal valve failure
- High engine mileage
- Crankcase pressure fluctuations
- Long-term exposure to engine vapours
Over time, the separator loses its ability to regulate crankcase pressure correctly.
Symptoms of a Failing AOS
A failing Air Oil Separator often produces noticeable warning signs.
Common symptoms include:
- Excessive white smoke from the exhaust
- Increased oil consumption
- Rough idle
- Vacuum leaks
- Whistling or squealing noises
- Check engine warning lights
- Oil residue in the intake system
- Excessive crankcase vacuum
- Difficulty removing the oil filler cap while the engine is running
These symptoms are common indicators that the separator requires replacement.
When Should the AOS Be Replaced?
Replacement is recommended whenever symptoms of failure appear.
The AOS should also be considered during:
- High-mileage maintenance
- Engine rebuilds Intake system servicing
- Preventative maintenance programmes
- Crankcase ventilation system repairs
Many Porsche specialists regard the Air Oil Separator as a preventative maintenance item on ageing M96 engines.
Why Replacement Matters
A failing AOS can affect engine performance, emissions and long-term reliability.
Benefits of replacement include:
- Improved idle quality
- Reduced exhaust smoke
- Lower oil consumption
- Correct crankcase pressure regulation
- Improved engine efficiency
- Reduced intake contamination
- Enhanced reliability
- Restoration of factory engine operation
Replacing a failing separator early can help prevent additional maintenance costs and drivability concerns.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610702602
The product you are viewing cross references to these numbers
- Porsche Boxster 987 2.7L 2005-08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
- 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 4 3.6L 2005-08
- Porsche Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
Also referred to as an oil separator hose or breather hose, this component plays a vital role in routing crankcase gases and oil vapours through the AOS system. This OE Match oil separator boot is a direct replacement part, manufactured to original specifications for precise fitment and long-term durability. It is installed between the air-oil separator and the crankcase, acting as a flexible connection that maintains a sealed system while accommodating engine movement.
Fits:
Porsche 987 Boxster 2.7L / 3.2L 2005 - 2008
Porsche 987C Cayman 2.7L / 3.4L 2005 - 2008
Porsche 996 Carrera 3.6L 2003 - 2005 (M96.03)
Porsche 997 Carrera 3.6L 2005 - 2008 COUPE / CABRIO (M96.05)
Diagram Ref No 10.
The boot allows crankcase gases to flow from the engine to the air-oil separator, where oil vapours are separated and returned to the engine while clean air is recirculated. If this hose fails or splits, it can lead to oil leaks, vacuum leaks, and poor engine performance.
Function
• Connects the air-oil separator to the crankcase
• Maintains sealed crankcase ventilation system
• Routes oil vapours for proper separation and recirculation
• Prevents oil leaks and vacuum loss
This component is essential for maintaining correct engine breathing and emissions performance.
Over time, the hose can become brittle, crack, or split due to heat and oil exposure. A failing hose can cause oil leaks, unmetered air entering the engine, and incorrect crankcase pressure. Replacing the boot ensures proper AOS system function, prevents oil contamination, and maintains smooth engine operation.
When to replace
• Oil leaks around engine or separator area
• Rough idle or vacuum-related issues
• Visible cracks or splits in hose
• Oil residue on engine components
• During AOS (air-oil separator) replacement
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610717550
The product you are viewing cross references to these numbers
- Porsche Boxster 987 MKII 2.9L 2009-12
- Porsche Boxster S 987 MKII 3.4L 2009-12
- Porsche Boxster 981 2.7L 2012-16
- Porsche Boxster 981 S / GTS 3.4L 2012-16
- Porsche Boxster 981 Spyder 3.8L 2016
- Porsche Boxster GTS 718 4.0L Manual (400 Bhp) 01/2019>>
- Porsche Boxster GTS 718 4.0L PDK (400 Bhp) 01/2019>>
- Porsche Boxster Spyder / Spyder RS 718 4.0L 01/2019>>
- Porsche Cayman 2.9L 987C MKII 2009-12
- Porsche Cayman S / R 3.4L 987C MKII 2009-12
- Porsche Cayman 2.7L 981 2013-16
- Porsche Cayman S / GTS 3.4L 981 2013-16
- Porsche Cayman GT4 3.8L 2015-16
- Porsche Cayman GTS 718 4.0L Manual (400 Bhp)
- Porsche Cayman GTS 718 4.0L PDK (400 Bhp)
- Porsche Cayman GT4 718 4.0L / GT4 RS 718 4.0L
A crankcase air-oil separator (AOS) that traps oil droplets and vapour from the engine’s blow-by gases and returns cleaned air to the intake system while keeping oil inside the engine’s lubrication system.
Sold individually. It is recommended to also inspect and, if necessary, replace associated hoses and seals when fitting a new separator to ensure full system integrity.
Fits:
Porsche 987.2 Boxster 2009 - 2012
Porsche 981 Boxster 2012 - 2016
Porsche 981 Boxster Spyder 2016>>
Porsche 982 Boxster GTS 4.0L 2017>>
Porsche 987C.2 Cayman 2009 - 2012
Porsche 981C Cayman 2014 2016
Porsche 981C Cayman GT4 2016>>
Porsche 982C Cayman GT4 4.0L 2017>>
Diagram ref no 16
This air-oil separator is an replacement unit designed to filter crankcase blow-by vapours on Porsche engines, separating oil mist from the air before routing clean air back into the intake or ventilation system.
Over time AOS units degrade - internal baffles can become clogged, seals can fail, or plastic can crack due to heat cycles. A faulty or clogged separator may allow oil vapour into the intake, causing:
• Increased oil consumption and oil-soaked intake/tracks.
• Blue or grey smoke from exhaust, rough idle, misfires or poor running.
• Sludge or carbon buildup, fouled sensors, and potential engine damage.
Replacing with a correct fresh separator restores clean crankcase ventilation, keeps oil inside, and helps maintain reliable performance and engine health.
You should replace the air-oil separator when:
• You notice oil in the intake system, oil residue around intake or throttle body, or excessive oil consumption.
• The separator is showing signs of age: cracks, hardened plastic, degraded seals, or clogging.
• Your engine exhibits excessive smoke, rough idling, or misfires potentially related to intake contamination.
• Carrying out engine maintenance, PCV servicing, or installing new hoses/seals.
• The separator hasn’t been replaced for many years or high mileage - preventive maintenance helps avoid more serious issues.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
0PB115099A
The product you are viewing cross references to these numbers