Boxstertips - Porsche Boxster White Smoke - What is Wrong - AOS

Porsche Boxster Exhausts White Smoke – What is Wrong

It is normal for the Porsche engines to exhaust white smoke on a cold start-up. This is caused by moisture burn-off. In more serious situations it is caused by oil or coolant burn off. Unfortunately one of the most common failures in the Porsche Boxster is the AOS which causes mass volumes of white smoke to emit from the exhaust.

A puff of white smoke that quickly clears is normal of the flat-six design. Don’t sit and let the car idle to warm up. Start it. Drive it. Keep the revs below 4,000 till the coolant and oil come up to temp (180-ish).

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Porsche Boxster Exhausts White Smoke only on Cold Starts?

If you only experience white smoke on cold starts and the white smoke dissipates when the engine is warm, you should be fine. Make sure that you have done your regular yearly maintenance on you MAF.

If your Porsche Boxster emits white smoke that persists beyond engine warm-up then you need to investigate deeper into the root cause of the issue.

Porsche Boxster Exhausts White Smoke – What to Check?

1.0 Check your Oil Level

Overfilling your oil can cause white smoke and damage your AOS. An oil overfill or an AOS not doing it’s job causes extra oil to end up in the air intake.

Be careful that you never overfill your oil in your Porsche Boxster.

If you (or your mechanic) overfilled your oil, then you need to remedy this asap. Overfilling your oil can cause many short and long-term issues including the premature failure of the AOS.

2.0 Check Your AOS

Check the vacuum on the oil filler cap. Remove the oil cap with the engine idleing (running.) If the vacuum is really strong and it takes a bit of force to pull the cap up then you might have a bad AOS. If the oil filler cap is easy to lift then you’re fine.

2.1 What is the AOS?

Boxstertips - White Smoke - Air Oil Separator
Boxstertips – White Smoke – Air Oil Separator

The Air Oil Separator (AOS) is part of the Positive Crankcase Ventilation (PCV) system. The AOS extracts minute amounts of oil mist from the crankcase, by liquefying the oil mist and returning to the crankcase. The clean air is then sent through the air intake.

As the AOS ages and fails, it cannot separate the oil from the crankcase oil mist and send oil directly into the air intake resulting in a large amount of white smoke. It only takes a few drops of oil in the air intake to create a lot of white smoke from the engine.

If your Porsche Boxster is spreading white smoke on a regular basis it is a telltale sign of the failed AOS. Address a failed AOS ASAP.

A failed AOS can cause liquid oil to enter the combustion chamber of your engine, this causes hydro-lock and may cause terminal damage to your engine.

Oil entering the air intake will also cause your spark plugs to foul and cause your catalytic converters to fail.

The AOS should be part of your maintenance schedule every 6 years or 75,000 miles (120,000 km), whichever comes first. Make sure that when you are replacing your AOS that you also replace the hoses and lines used by the AOS.

2.2 Example of a Failed AOS in Action

This video clearly depicts the amount of white smoke drivers will experience when their AOS is failing (or failed.)

Ryan Coultas has a Great Example of a Failed AOS

2.3 Replacing your AOS

Replacing your AOS is covered in PROJECT 9 in the book 101 Projects for Your Porsche Boxster .

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101 Projects for Your Porsche Boxster (Motorbooks Workshop)
616 Reviews
101 Projects for Your Porsche Boxster (Motorbooks Workshop)
  • Used Book in Good Condition
  • Dempsey ., Wayne (Author)
  • English (Publication Language)
  • 312 Pages - 01/08/2011 (Publication Date) - Motorbooks (Publisher)
Boxstertips - 101 Projects for your Porsche Boxster
Boxstertips – 101 Projects for your Porsche Boxster

When replacing your AOS, make sure to get a new Porsche AOS Boot Clamp Assembly”. This item comes with a compression clip for easy installation, otherwise, you will need to source a spring clamp removal tool .

Oil / Air Separator Boot Clamp. Porsche 986 Boxster / 996 2001
30 Reviews
Oil / Air Separator Boot Clamp. Porsche 986 Boxster / 996 >>2001
  • A brand-new Genuine PORSCHE OE part
  • 99951263000
BETOOLL 9pcs Wire Long Reach Hose Clamp Pliers Set Fuel Oil Water Hose Auto Tools
2,139 Reviews
BETOOLL 9pcs Wire Long Reach Hose Clamp Pliers Set Fuel Oil Water Hose Auto Tools
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  • For replacement of fuel, oil, and water hose.
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Porsche AOS Replacement Parts



2009 - 2015 Porsche Boxster AOS - PORSCHE Oil Separator Brand New GENUINE PORSCHE
  • Oil Separator
  • Brand New, Original Part.
  • Part #9A110704202
  • Please see description below for compatible cars

AOS Porsche Part # 996 107 023 04

YearMakeModelTrimEngine
1997PorscheBoxsterBase Convertible 2-Door2.5L 2480CC H6 GAS DOHC Naturally Aspirated
1998PorscheBoxsterBase Convertible 2-Door2.5L 2480CC H6 GAS DOHC Naturally Aspirated
1999PorscheBoxsterBase Convertible 2-Door2.5L 2480CC H6 GAS DOHC Naturally Aspirated
2000PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2000PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2001PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2001PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2002PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2002PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
Porsche Part # 996 107 023 04

AOS Porsche Part # 996 107 026 01

earMakeModelTrimEngine
2003PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2003PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2004PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2004PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2004PorscheBoxsterS Special Edition Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2005PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2005PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2006PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2006PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2007PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2007PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
2008PorscheBoxsterRoadster Convertible 2-Door2.7L 2687CC H6 GAS DOHC Naturally Aspirated
2008PorscheBoxsterRoadster S Convertible 2-Door3.2L 3179CC H6 GAS DOHC Naturally Aspirated
AOS Porsche Part # 996 107 026 01

AOS Porsche Part # 9A1 107 042 02

YearMakeModelTrimEngine
2009PorscheBoxsterRoadster Convertible 2-Door2.9L 2893CC H6 GAS DOHC Naturally Aspirated
2009PorscheBoxsterRoadster S Convertible 2-Door3.4L 3387CC H6 GAS DOHC Naturally Aspirated
2010PorscheBoxsterRoadster Convertible 2-Door2.9L 2893CC H6 GAS DOHC Naturally Aspirated
2010PorscheBoxsterRoadster S Convertible 2-Door3.4L 3387CC H6 GAS DOHC Naturally Aspirated
2011PorscheBoxsterRoadster Convertible 2-Door2.9L 2893CC H6 GAS DOHC Naturally Aspirated
2011PorscheBoxsterRoadster S Convertible 2-Door3.4L 3387CC H6 GAS DOHC Naturally Aspirated
2012PorscheBoxsterRoadster Convertible 2-Door2.9L 2893CC H6 GAS DOHC Naturally Aspirated
2012PorscheBoxsterRoadster S Convertible 2-Door3.4L 3387CC H6 GAS DOHC Naturally Aspirated
2013PorscheBoxsterRoadster Convertible 2-Door2.9L 2893CC H6 GAS DOHC Naturally Aspirated
2013PorscheBoxsterRoadster S Convertible 2-Door3.4L 3387CC H6 GAS DOHC Naturally Aspirated
2014PorscheBoxsterRoadster Convertible 2-Door2.9L 2893CC H6 GAS DOHC Naturally Aspirated
2014PorscheBoxsterRoadster S Convertible 2-Door3.4L 3387CC H6 GAS DOHC Naturally Aspirated
2015PorscheBoxsterRoadster Convertible 2-Door2.9L 2893CC H6 GAS DOHC Naturally Aspirated
2015PorscheBoxsterRoadster S Convertible 2-Door3.4L 3387CC H6 GAS DOHC Naturally Aspirated
AOS Porsche Part # 9A1 107 042 02

From Youtube

Ben Burner with an Excellent Video on the AOS replacement

Other Concerns for the Cause of Exhaust Smoke:

The primary reason for white smoke in your Porsche Boxster will be a failing (or failed) AOS. That being said we will also outline various other and more serious issues for the white smoke. We have seen all of these issues many times before during track days.

1. The Dreaded MAYO

When you are testing your AOS using the Oil Filler cap and looking for suction from your engine, do a thorough examination on the underside of the cap. It is not uncommon to see yellow-ish creamy emulsion form (referred to as Mayo) under the oil filler cap of Porsche Boxsters and Caymans, particularly after short journeys during cold weather.

Boxstertips - White Smoke - The Dreaded Mayo.
Boxstertips – White Smoke – The Dreaded Mayo.

Unfortunately, the formation of Mayo is very indicative of coolant mixing with your oil. When this happens you will see a lot of white smoke during acceleration. The primary cause for this is a blown head gasket.

This is a prevalent event on Driver Education Days or Open Lapping Nights and virtually the entire track knows that you missed a shift and blew your head gasket.

2. Damaged Cylinder Head

A damaged (cracked or warped) cylinder head will cause your engine to lose compression and misfire because there is too much heat. The excessive heat build-up will cause the cylinder head to crack because engine components have warped.

3. Cracked Engine Block

If your Boxster is emitting white smoke continuously, it is possible that you have a cracked engine block.

4. Blown Valve Stem Seal

If you see blue or grey smoke after sitting at a stop for 30 to 60 seconds and then beginning to throttle. The valve stem seal regulates the amount of oil that is applied to lubricate the valve stem. Bad valve stem seals nearly always show an intermittent problem of oil burning. However, the smoke will eventually disappear after long engine operation or during long periods of hot weather

5. Failed Piston Rings

If the smoke coming from the exhaust during strong acceleration is a blue or grey color it is more probable that oil is leaking directly into the combustion chamber as a result of a failed piston ring(s). NOTE:  worn piston rings and valve guides will burn oil and smoke during all times of engine operation and never disappear.

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