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Air Oil Separator Replacement
 
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Pelican Technical Article:

Air Oil Separator Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$160

Talent:

**

Tools:

T30, 10mm wrench

Applicable Models:

Porsche 955 Cayenne GTS (2008-10)
Porsche 955 Cayenne S (2008-10)
Porsche 955 Cayenne Turbo (2008-10)
Porsche 970 Panamera 4S (2010-14)
Porsche 970 Panamera 4S Executive (2014)
Porsche 970 Panamera GTS (2013-14)
Porsche 970 Panamera S (2010-14)
Porsche 970 Panamera S E-Hybrid (2014)
Porsche 970 Panamera Turbo (2010-14)
Porsche 970 Panamera Turbo Executive (2014)
Porsche 970 Panamera Turbo S (2012-14)
Porsche 970 Panamera Turbo S Executive (2014)

Parts Required:

AOS

Hot Tip:

Work carefully on the plastic pieces

Performance Gain:

Functioning AOS

Complementary Modification:

Oil and filter

The engine air-oil separator (AOS) is an emissions device that is responsible for collecting residual gases and vapors contained inside the crankcase and funneling them back into the intake manifold where they can be burned in the combustion chamber. This reduces the overall emissions of the engine.

When the separator fails, you will begin to see a large increase in the overall vacuum in the engine crankcase. In the most extreme cases, the air-oil separator fails to separate the oil from the air, and oil is then sucked into the intake manifold. Oil in the intake system is not healthy for the engine, and it can foul spark plugs and destroy catalytic converters. The failure of the air-oil separator is often but not always, accompanied by large amounts of white smoke exiting the vehicle's exhaust and a generally poor running engine. You may experience a check engine light (CEL), since the oil being drawn into the intake can affect the mixture level. The oil cap may be very difficult to remove when the engine is running due to high vacuum levels.

The AOS on the Porsche Cayenne is built into a cover on the top left cylinder bank and cannot be replaced separately. You need to replace the complete piece when the AOS fails.

You will need to remove the engine covers before you can replace the AOS so please see our article on engine cover removal before starting this job.

The AOS is connected to the front of the motor by a hose that runs from the top of the AOS (red arrow) to the intake manifold (yellow arrow).
Figure 1

The AOS is connected to the front of the motor by a hose that runs from the top of the AOS (red arrow) to the intake manifold (yellow arrow). Squeeze in the tabs and remove this hose. The oil return line (green arrow) will be removed after the cover or AOS is off.

Next, remove the cross over hose (red arrow) from the two separators on top of each cylinder head (yellow arrows).
Figure 2

Next, remove the cross over hose (red arrow) from the two separators on top of each cylinder head (yellow arrows).

If you are going to be working on your Cayenne it is a very good idea to make your own homemade AOS hose clip separator.
Figure 3

If you are going to be working on your Cayenne it is a very good idea to make your own homemade AOS hose clip separator. All of the AOS hoses on the Cayenne are the same size so this will work for all of them. Take a small but thick wire and bend it to the size of the inside opening of the hoses and file both points down so they will slip in easier (red arrows).

You can now safely slip your homemade tool between the plastic clip on the hoses and the housings and remove the hoses without worrying about breaking very expensive hoses.
Figure 4

You can now safely slip your homemade tool between the plastic clip on the hoses and the housings and remove the hoses without worrying about breaking very expensive hoses.

The tool (red arrow) makes removing the hoses safe and easy and should be kept handy in your toolbox.
Figure 5

The tool (red arrow) makes removing the hoses safe and easy and should be kept handy in your toolbox.

With the crossover hose off inspect it.
Figure 6

With the crossover hose off inspect it. If it looks like this (red arrow) or has any buildup of sludge you are going too long between oil changes.

Remove the six T30 Torx bolts (red arrows) on the two covers as well as the small 10mm bolt holding the harness at the rear of the cover (yellow arrow)
Figure 7

Remove the six T30 Torx bolts (red arrows) on the two covers as well as the small 10mm bolt holding the harness at the rear of the cover (yellow arrow)

You do not need to remove the coil cover but you cannot get the AOS out without loosening it first.
Figure 8

You do not need to remove the coil cover but you cannot get the AOS out without loosening it first. Wiggle the AOS off; there is an O-ring that may cause it to stick a little.

Tilt the AOS back and disconnect the oil to engine line (red arrow).
Figure 9

Tilt the AOS back and disconnect the oil to engine line (red arrow).

You can now replace the entire cover that makes up the AOS.
Figure 10

You can now replace the entire cover that makes up the AOS.

If you are leaving the cover off for any time make sure to plug the holes (yellow arrows) to prevent anything accidentally falling in the valve cover.
Figure 11

If you are leaving the cover off for any time make sure to plug the holes (yellow arrows) to prevent anything accidentally falling in the valve cover. Be careful with the oil return line, as it is made of plastic and gets brittle. Our line had cracked and someone had grafted a small section of rubber hose on the end of it (red arrow). Installation is the reverse of removal.




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