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MajorVery commonEngine

Porsche Cayenne: Air Oil Separator (AOS) failure causing oil consumption and smoke

Air Oil Separator (AOS) failure causing oil consumption and smoke is a very common engine fault on the Porsche Cayenne on the 2002–2010 cars, and we rate it major. Putting it right costs $700 to $1,800 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 23 documented faults on the Porsche Cayenne.

Vehicle
Porsche Cayenne
Years
2002–2010
Fuel
petrol
Gearbox
auto
System
Engine

This page covers the Porsche Cayenne as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Porsche Cayenne faults23 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph of the PCV / oil separator yet. We would rather show none than show a picture of a different part.

What goes wrong

The Air Oil Separator (AOS or PCV valve assembly) is a crankcase ventilation component that separates oil mist from blow-by gases before returning them to the intake. When it fails — typically from diaphragm rupture or clogging — engine oil is drawn into the intake manifold in quantity. This causes blue smoke at startup and under load, elevated oil consumption, fouled spark plugs, and can trigger catalyst damage over time. Affects both V6 3.2L and V8 4.5L engines across 955 and early 957.

What you would notice

  • Blue smoke on startup or after engine braking
  • Oil consumption higher than 0.5L per 1000 km
  • Oil residue in intake ducting or throttle body
  • Rough idle after a cold start
  • Fouled or oil-coated spark plugs

How to check it

Where to look. Top of engine between cylinder banks, connected to crankcase ventilation and intake manifold

Check engine oil level — drop of more than 1L per 3000 km is a red flag. With the vehicle cold after an overnight sit, start the engine and observe exhaust for initial blue smoke. Request service history showing AOS replacement. If a workshop inspection is possible: Remove the intake duct between the airbox and throttle body and inspect inside for oily residue.

Parts involved: PCV / oil separator.

What it costs to put right

$700 to $1,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “Has the AOS / air oil separator been replaced?”
  • “How often has oil been topped up between services?”
  • “Is there a Porsche specialist service history?”

Now check the Porsche Cayenne you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

Porsche Cayenne buyer questions

Is air oil separator (aos) failure causing oil consumption and smoke serious on a Porsche Cayenne?

We rate it major and very common on the Porsche Cayenne. The Air Oil Separator (AOS or PCV valve assembly) is a crankcase ventilation component that separates oil mist from blow-by gases before returning them to the intake. When it fails — typically from diaphragm rupture or clogging — engine oil is drawn into the intake manifold in quantity. This causes blue smoke at startup and under load, elevated oil consumption, fouled spark plugs, and can trigger catalyst damage over time. Affects both V6 3.2L and V8 4.5L engines across 955 and early 957.

How much does it cost to fix on a Porsche Cayenne?

$700 to $1,800 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Porsche Cayenne years are affected?

Our research records this fault on the 2002–2010 Porsche Cayenne. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Check engine oil level — drop of more than 1L per 3000 km is a red flag. With the vehicle cold after an overnight sit, start the engine and observe exhaust for initial blue smoke. Request service history showing AOS replacement. If a workshop inspection is possible: Remove the intake duct between the airbox and throttle body and inspect inside for oily residue. Look here: Top of engine between cylinder banks, connected to crankcase ventilation and intake manifold