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- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
This Air/Oil Separator product ref 996.107.023.55 also includes the rubber below 996.107.237.52 and jubilee clip 999.512.551.01
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 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
Click pictures for large parts diagram.
Diagram Ref No 1.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610702355
The product you are viewing cross references to these numbers
- 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
Fits:
Porsche 996 C2 / C4 / C4S 3.6L 2002-05
Porsche 997.1 C2 / C2S / C4 / C4S 3.6L 2005-08
Click 'Zoom in' for large parts diagram.
Diagram ref no 5
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610714530
The product you are viewing cross references to these numbers
- 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 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
This AOS oil / air separator by OE Match is listed for Porsche 996 and 997.1 3.6L applications, including the Carrera variants detailed in the fitment section.
Fits
- Porsche 996 (911) 1997–2005
- Porsche 996 Carrera 2 3.6L 09/2001–2005
- Porsche 996 Carrera 4 3.6L 09/2001–2005
- Porsche 996 Carrera 4S 3.6L 09/2001–2005
- Porsche 996 Turbo 2000–05
- Porsche 997 (911) Mk1 2005–08
- Porsche 997 Mk1 Carrera 2 3.6L 2005–08
- Porsche 997 Mk1 Carrera 4 3.6L 2005–08
Check fitment for your specific vehicle (model, year, engine) before ordering.
Diagram Ref No 1.
What This Product Does
The air/oil separator forms part of the engine crankcase ventilation system. It removes suspended oil droplets from blow-by gases before the gases are directed towards the intake. Separated oil can return to the crankcase, helping to limit the amount of liquid oil reaching the intake tract.
Functions
- Separates oil mist from crankcase gases.
- Supports controlled crankcase ventilation.
- Returns separated oil towards the engine crankcase.
- Routes treated blow-by gases into the intake system.
- Helps prevent excessive oil contamination within the intake.
Technical Details
- Part number: 99610702652.
- Related earlier reference: 99610702651.
- Component type: air/oil separator for the crankcase ventilation system.
- Diagram application: Porsche 996 Carrera 2, Carrera 4 and Carrera 4S with M96.03 engine from 2002.
- Diagram application: Porsche 997.1 3.6L Coupé and Cabriolet with M96.05 engine, 2005–08.
Symptoms of Fault
- Heavy white or blue exhaust smoke, particularly after starting or idling.
- Increased engine oil consumption.
- Rough, unstable or hunting idle.
- Whistling or honking sounds from the crankcase ventilation system.
- An oil filler cap that is unusually difficult to remove because of excessive vacuum.
- Oil deposits around the throttle body or intake pipework.
- Misfire or mixture-related faults where oil or unmetered air enters the intake.
- Cracked, brittle or leaking associated breather lines.
Why Replacement Matters
A deteriorated separator may allow liquid oil to pass into the intake or create abnormal crankcase vacuum. Replacing the faulty component helps restore the intended ventilation path and may address smoke, oil consumption or idle problems caused by the AOS. The adjoining vent lines, seals and connections should also be inspected because age-hardened pipes can crack when disturbed. Occasional brief smoke from a flat-six engine does not by itself confirm separator failure, so oil level, breather integrity and other possible causes should be checked before replacement.
FAQs
- Does exhaust smoke always indicate AOS failure?
No. Oil overfilling and other engine faults can produce similar symptoms, so diagnosis is recommended. - Can a faulty separator cause misfires?
Yes. Oil entering the intake or a vacuum leak within the breather system may affect combustion and foul spark plugs. - What else should be inspected?
Check the oil level and examine the vent lines, connections, seals and intake pipework for oil residue, cracks or leaks. - Is this the same separator used on a Boxster?
AOS problems are also discussed in relation to Boxster models, but this part is listed for the Porsche 996 and 997.1 applications shown above.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610702652
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 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
Crankcase Breather System (Air/Oil Separator)
The crankcase breather system, also known as the air/oil separator (AOS), is a critical engine component that should be replaced every 30,000 miles—or sooner if signs of failure appear.
When the system fails, it can cause:
- Vacuum leaks due to cracked hoses or a damaged air/oil separator
- Oil consumption and fouled spark plugs, as oil is drawn into the intake
- Increased crankcase pressure, which can lead to gasket leaks and other engine issues
Preventative Maintenance
Preventative maintenance is always the best approach. Our comprehensive Crankcase Breather Hose Kit includes all the components you need to replace the system properly. We also recommend performing an engine oil change at the same time to ensure peak performance and longevity.
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 997 C2 3.6L
Porsche 997 C4 3.6L
Click pictures for large parts diagram.
Diagram Ref No 1, 4 , 5
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
OILSEPARATOR.997.1.OEM
The product you are viewing cross references to these numbers
This kit is comprised of the following items:
