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Oil Separators & Vent lines
By OE Match
- 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Related, superseded, cross reference or alternative numbers for comparison.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:
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
Fits:
Porsche 997.1 Carrera 2S / 4S 3.8L
Kit contains 3 oil separators, feed and return lines and breather lines.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
OILSEPARATOR.997S.1.OEM
The product you are viewing cross references to these numbers
This kit is comprised of the following items:
- 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 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 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
Fits:
Porsche 997.1 Carrera 4/ Carrera 4S 3.8L 2004-08
Click 'Zoom in' for large parts diagram.
Diagram ref no 7
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99710714301
The product you are viewing cross references to these numbers
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
OE Match breather line for cylinders 4–6 on the listed Porsche 997.1 Carrera applications, this pipe connects the primary and secondary oil separators within the crankcase ventilation system.
Fits
- Porsche 997.1 Carrera 4/ Carrera 4S 3.8L 2004-08
- 997 MK1 Carrera 2S 3.8L 2005-08
- 997 MK1 Carrera 4S 3.8L 2005-08
Diagram ref no: 5
Check fitment for your specific vehicle (model, year, engine) before ordering.
What This Product Does
The line provides a passage between the oil separators, allowing crankcase gases to move through the ventilation circuit. It is a connecting pipe rather than an oil separator: oil separation takes place in the associated separator units.
Functions
- Connects the primary and secondary separator units.
- Carries ventilation gases through the cylinders 4–6 circuit.
- Provides a sealed connection within the breather system.
Technical Details
- Part reference: 99710714603.
- Brand: OE Match.
- Component: crankcase breather / vent line.
- Cylinder assignment: 4–6.
- Connection: primary separator to secondary separator.
Symptoms of Fault
Inspect the ventilation pipework if there is visible cracking, oil mist near a connection, an uneven idle or a whistling sound. Increased oil use and exhaust smoke can also accompany ventilation-system faults, but these symptoms do not establish that this particular line has failed.
Why Replacement Matters
A damaged or obstructed pipe can affect the ventilation circuit. Renewing a confirmed faulty line addresses that defect; it does not repair a failed separator or another source of oil consumption. During replacement, examine adjoining connections, seals and supporting components for deterioration.
FAQs
Does exhaust smoke prove the breather line needs replacing?
No. Separator faults, an incorrect oil level and other engine problems can produce similar signs. Establish the cause before selecting replacement parts.
What should be checked alongside this pipe?
Inspect neighbouring breather lines, separator connections and seals. Check the engine oil level as part of the diagnosis.
How should compatibility be confirmed?
Compare reference 99710714603 with the original component and verify the model, engine and production details. The supplied diagram identifies this line for the M97.01 3.8L application.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99710714603
The product you are viewing cross references to these numbers
- 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 4 3.6L 2005-08
Keep your Porsche engine breathing correctly with this OE Match Crankshaft Ventilation Hose, designed for selected Porsche 996 and Porsche 997.1 models. Manufactured to OE specifications, this high-quality replacement hose forms an essential part of the engine's crankcase ventilation system, safely transferring crankcase vapours back into the intake system where they are reburned during normal combustion.
Fits:
- 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 4 3.6L 2005-08
Diagram Ref No 19
What This Product Does:
- The crankcase ventilation hose provides a path for filtered crankcase gases (blow-by, vapours, oil mist) to be routed from the engine’s crankcase or oil separator back into the intake or PCV (positive crankcase ventilation) system rather than being vented uncontrolled.
- It helps maintain correct engine vacuum/pressure balance within the crankcase, removes oil vapours, prevents buildup of excess pressure that could cause leaks or gasket failures, and supports emissions compliance.
Symptoms Of Wear Or Failure:
- Visible cracks, splits or brittleness in the hose; rubber/engine bay hoses degrade under heat/oil/vapour over time.
- Oil residue, grime or wetness around the hose or its connectors — if vapour is leaking, you may see oil-moisture deposit around the breather circuit.
- Mis-fires, rough idle or engine running poorly — because un-metered air (via a damaged breather hose) may be introduced, altering the air/fuel ratio.
- Check Engine Light (CEL) or fault codes concerning intake air leak, crankcase pressure or PCV system faults.
- Oil smells in the engine bay / smoke from the breather area — indicating the hose may no longer be securing the vapours correctly.
- Protects engine internals & seals: Proper ventilation prevents excessive crankcase pressure which can force oil past seals or gaskets, causing leaks or damage.
- Maintains performance & emissions: A damaged breather hose can upset engine vacuum and air-fuel mixture, affecting power, idle quality and emissions.
- Prevents bigger failures: A failing hose is inexpensive; ignoring it could lead to more costly repairs (seal replacement, engine bay oil contamination, intake system clean-up).
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610622352
The product you are viewing cross references to these numbers
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
Engine oil separator breather hose. From air oil separator to engine.
Fits:
Porsche 997.1 Carrera S / Carrera 4S 2005-08
Diagram ref no 8
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99710714502
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 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
OE Match oil separator for the engine breather lines on Porsche 997.1 Carrera 2S and Carrera 4S 3.8L models from 2005 to 2008. Fitted within the crankcase ventilation system, this component helps manage oil mist carried through the breather circuit and supports correct engine ventilation. The same part fits the left or right side, with 2 required per vehicle.
Sold individually
Fits:
Porsche 997 3.8L Carrera 2S / 4S 2005 - 2008
This oil separator forms part of the engine crankcase breather system. It works within the breather lines to help separate oil mist from crankcase vapours before they continue through the ventilation system.
- Forms part of the engine crankcase breather system
- Helps separate oil mist from breather vapours
- Supports correct crankcase ventilation
- Helps manage oil contamination within the breather system
- Fits either left or right side
- Replaces damaged, blocked or deteriorated oil separators
- Suitable for breather system servicing and engine maintenance
- Supplied as an OE Match replacement part.
Why Replace This Part?
- Increased oil residue within the intake or breather system
- Irregular crankcase ventilation
- Oil vapour contamination
- Breather system leaks
- Poor engine running associated with ventilation faults
- Deteriorated or damaged breather connections.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99710713800
The product you are viewing cross references to these numbers
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
Oil Separator - Main Centre unit - is a direct-fit replacement for the factory crankcase ventilation system component used on Porsche 911 (997) Carrera 3.8L 2S / 4S engines. This separator plays a vital role in maintaining crankcase pressure equilibrium by separating oil mist from blow-by gases before routing clean air back into the intake manifold.
Porsche 997 3.8L Carrera 2S / 4S 2005 - 2008
• Position: Engine – main centre, crankcase ventilation housing
• Benefits: OE-style fit, improved oil vapor separation, durable diaphragm construction
• Installation: Direct-fit replacement; verify hose routing and seals during reassembly
• You see oil residue or smoke from the exhaust or intake
• The engine shows rough idle, whistling sounds, or high vacuum
• Oil consumption has increased significantly
• During engine service or PCV system maintenance
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99710703801
The product you are viewing cross references to these numbers
OEMatch Oil Separators & Vent lines — Durability, Sealing, Performance
The oil separator and vent line system manages crankcase ventilation on Porsche engines by separating oil vapour from blow-by gases and returning cleaner air to the intake. Properly functioning separators and breather hoses reduce oil contamination and help preserve throttle response, idle quality and long-term engine cleanliness. OEMatch supplies replacements and related hoses prepared for Porsche applications to support routine maintenance and rebuilds.
Available Types- Oil separators (breather housings)
- Breather hoses and vent lines
- Seals, grommets and connection fittings
OE (Original Equipment) refers to parts matching original specifications for the oil separators & vent lines and may be supplied by alternative manufacturers. Aftermarket parts offer alternative options, sometimes with enhanced features or better value. OEMatch supplies non-OEM oil separators & vent lines engineered as direct-fit alternatives to OEM parts, made to original-spec dimensions and tolerances for Porsche models.
The oil separator and vent system controls crankcase pressure, removes oil vapour from circulating gases and keeps intake air free of oil droplets.
When functioning correctly the system prevents oil entering the intake tract, reduces smoke and limits carbon build-up on inlet valves and ports. OEMatch also maintains a catalogue of more than 4,000 individual part numbers and over 8,700 OE cross-references to aid correct selection for Porsche applications.
- Restores clean airflow and stable crankcase pressure
- Reduces oil leaks, blue smoke and carbon accumulation
- Supports consistent idle and throttle response
- Clogged or degraded internal membranes inside separators
- Cracked, hardened or collapsed breather hoses due to heat and age
- Worn seals, grommets or connection points causing leaks
- Vacuum leaks affecting idle and throttle response
- Sludge or condensation build-up inside vent lines
Replacing a worn or damaged separator or vent line restores correct crankcase breathing and helps avoid progressive engine issues such as oil contamination, valve deposits and inconsistent running. Fitted components specified for Porsche engines help preserve emissions performance and reduce the risk of oil reaching the intake tract. Select parts that match the original connections and materials for reliable long-term operation.
Advantages- Direct-fit replacements engineered to match original dimensions and tolerances
- Components manufactured in heat- and oil-resistant materials for longevity
- Catalogue cross-references and part numbers to support correct selection for Porsche models
Installation should be carried out by a qualified technician following model-specific procedures and torque settings. Use calibrated tools and new fasteners where specified. If you are unsure about hidden sensors or routing, seek professional installation to ensure correct sealing and operation.
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