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Porsche 911 Air Oil Separator
 
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Pelican Technical Article:

Porsche 911 Air Oil Separator

Time:

3 hours3 hrs

Tab:

$130 to $165

Talent:

****

Tools:

All of them

Applicable Models:

Porsche 996 Carrera models (1999-05)
Porsche 997 Carrera models (2005-08)

Parts Required:

New oil separator

Hot Tip:

Take your time and make sure you don't drop anything down into the engine

Performance Gain:

No more smoke

Complementary Modification:

Change the oil

The engine air-oil separator 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.

On the 1998-2005 Carreras, the engine air-oil separator is located at the top left rear corner of the engine. For the 2006-2008 Carreras, Porsche redesigned the system and moved the AOS to the top of the engine under the right side intake.

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 at the very least. The failure of the air-oil separator is often but not always, accompanied by huge amounts of white smoke exiting the vehicle's exhaust and a generally poor running engine. You may experience a check engine light (CEL) as 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. In addition, you may hear a high-pitched squeal from the engine when it's running because air is being sucked in past the crankcase seal due to the extreme vacuum inside the case.

The proper method to test for the failure of the unit is to measure the engine crankcase vacuum with a slack tube manometer. Normal crankcase pressure, measured at the oil filler cap ranges from about 4-7 inches of water (drill a hole in the top of an old oil filler cap and attach the gauge there). When the air-oil separator fails, the intake manifold vacuum will draw into the crankcase and the levels will reach 9-12 inches or more. If you don't have a slack tube manometer (most of us don't), then you can use a standard vacuum gauge and/or get a rough feel for the level of vacuum pulled by comparing it to a normal running car.

On the pre 2006 cars here are basically two ways to change the oil separator. The easiest is to drop the engine out of the car. This allows you full access to the lines and connections of the separator. The other method is to remove the separator with the engine in the car. It's a bit daunting, but we have come up with a method for removing it. On the 2006 and later cars Porsche redesigned the AOS, and while it is still easier to do this with the engine out of the car, it is a lot easier than performing the work on an earlier car.

Begin by first disconnecting the battery. You'll be working around the starter motor and there is always a 12V load going to the starter motor. If you accidentally touch it, you can injure yourself or cause a variety of problems with the car's electrical system. Be safe, take the extra time to disconnect it. Another good tip here is to use Ziploc bags to neatly hold all of the various nuts and bolts you will be removing from the engine.

Open the engine lid and begin by removing the airbox. Loosen and remove the 13mm bolt at the very front of the airbox (996), and the hose clamp holding the boot to the throttle body. You'll also have to unplug the connector to the MAF by squeezing the connector. Now pull the boot off the throttle body and remove the airbox from the engine bay (on 3.8L cars and you will have to remove the electrical connection attached to the vacuum line for the resonance valve).

In order to access the oil separator, a lot of stuff has to come off the engine. First remove the throttle body. The throttle body is held in place on the intake plenums by four 10mm bolts and a 10mm nut attached to an eccentric bracket at the bottom. Remove all four bolts, taking care not to drop the bolts into the engine bay. You'll now need to disconnect either the throttle cable (on early cars) or the electrical connector for the throttle (on later cars). The throttle cable ferrule runs along a plastic cam on the side of the throttle body. If you manually open the throttle, the cable tension will go slack, allowing you to unhook the ferrule from the shoulder in the plastic cam. On cars with electronic throttle bodies, simply unhook the electrical connector.

On the earlier cars rotate the throttle body over to access the hose connection on the backside. Use a pair of pliers to loosen and remove the hose clamp holding the hose onto the throttle body. Don't forget to pull the O-ring out of the intake plenum that seals the throttle body. Now set the throttle body aside in a safe place.

Once the throttle body is removed, you'll need to remove the intake plenums. While the Porsche technical manual recommends that you remove both plenums, for the 2006 and later Carreras I recommend what I have found to be an easier way. You only need to remove both plenums if you are going to remove the AOS from the top of the engine, but by removing the two T30 screws on the AOS mount, you can swing it out of the way and remove the separator through where the A/C compressor use to be. If you need to remove the second plenum for additional work then you will not need to move the separator mount, but it is a very tight fit on the second plenum, and I have found removing the mount screws easier.

Begin by removing the air hose connection to the oil separator. Squeeze the black plastic connector to disconnect the hose from the plenum. Once free, set the hose connection aside. Now loosen the hose clamps securing the plenum to each manifold. A good idea here is to loosen the inner hose clamps first and then rotate the plenum to help break the seal that may have formed between the rubber, then tighten the inner and loosen the outer clamps and do the same to break the connection between the rubber seals and the intake manifolds. Sometimes they can stick together making removal a bit difficult and this will help free them up. As you will note there is not much room to work and anything that makes it easier will help. Remove the front plenum only after the left intake manifold is loosened/unseated. Slide the rubber seals onto the plenum and wiggle the plenum out. Once the front plenum is removed, follow the same procedures and remove the rear plenum from the engine bay (this is for the 1998-2005 cars only as you do not need to remove the second plenum in the later cars if you loosen the AOS mount).

At this point we are going to break the instructions down for the 1998-2005 Carreras and the 2006-2008 Carreras.

(1998-2005 Carreras) Remove the two 8mm screws holding the hose connection to the front of the left intake manifold. These screws also hold the retaining plate for a vacuum solenoid at the left of the hose connection. Once free, maneuver the hose, plate and solenoid up and out of the way.

It is a good idea to look around the engine bay for anything that may be hanging up, or any loose nuts or bolts. The last thing you need is to drop a stray bolt down into the cylinder head. Take a little extra time and be patient.

Now comes the hardest part of the job, removing the small Torx bolts that hold the intake manifold to the cylinder head. I've found that a combination of 1/4" drive extensions and U-joints really help out here. The key here is to have enough clearance. The other really helpful step is to remove the coolant tank from the car. You won't have a lot of room to work with, unfortunately. One handy tip is to loosen each bolt to the point where they can be pulled out of the manifold, then use a telescoping magnet to keep from dropping them in the engine bay. Also take note of the accessory bracket on the very front of the intake manifold. Don't forget to re-install this later.

Now carefully pull the intake manifold off the cylinder head. You'll also have to route the vacuum hoses and wiring harnesses over the manifold as you pull the manifold out of the engine bay. As soon as you get the manifold off, stuff rags or paper towels down into the cylinder head ports. This is good insurance against foreign objects falling into the motor.

At this point, you will have access to the top of the oil separator. Squeeze the black plastic connector to release the vacuum connection from the oil separator.

Now jack up the rear of the car and secure it on jackstands. If you aren't sure how to do this, please refer to our article on jacking up your 996 (Pelican Technical Article: Jacking Up Your Porsche 911 Carrera). Slide under the car and locate the bottom of the oil separator. It will be located on the left side of the engine, right where the transmission and engine mate up to each other.

You see a few different connections below. The first thing to disconnect is the bellows on the underside of the oil separator. Removing this hose clamp can be rather frustrating because of the amount of clearance you have in-between the separator and the crossbeam under the engine. After you have removed the hose clamp, pull the bellows down and off the bottom of the separator. Now squeeze the black plastic connector above the bellows to release the vacuum hose connection. As with the bellows, this will be a tight fit.

Once both of the connections are off, remove the two 13mm bolts holding the separator to the engine and carefully pry the separator off the engine. As you pull the separator off, you'll see the nipple piece that extends into the engine.

Installation is the reverse of removal. DO NOT forget to remove the rags from the intakes before re-installing the plenums!

(2006-2008 Carreras) For the 2006-2008 Carreras, you are going to be removing the air conditioning compressor and power steering reservoir. To do this you will first have to remove the accessory belt. To release the tension on the belt attach a 24mm socket to a breaker bar, place it on the idler arm and turn it clockwise (see Pelican Technical Article: Replacing Belts on the Porsche 911 Carrera). After you have removed the accessory belt you will need to remove the power steering reservoir on the right side of the engine. Open the power steering fluid reservoir and use either a syringe or turkey baster to suction out as much of the power steering fluid as you can. Once the reservoir is empty, remove the 10mm nut securing the reservoir to the bracket, then rotate the bayonet lock tab counter-clockwise to remove the power steering fluid reservoir from the car.

The next step is to remove the A/C Compressor from the engine with the lines still attached. The compressor is held in place by three long 13mm bolts. Remove the two front bolts along the front edge. In order to get to the remaining A/C Compressor mounting bolt, you'll need to remove the temperature sensor mounted in the right (passenger) side manifold, in between the first set of runners. The sensor sits in a rubber sleeve that fits into a groove on the intake manifold. It's difficult to see it, but it will slide out to the right.

You can now access the remaining compressor bolt from in between the intake manifold. You'll need a combination of extensions and U joints. The long bolt needs to be held in it upward position to remove the compressor. Once the compressor is free, unplug the electrical ground connector. After the compressor is removed, lay down a rag or towel to protect the paint of the car and lay the compressor off to the side of the engine.

Once the compressor is out of the way you will have lots of room to reach in and remove the two lines coming from each cylinder bank and the line going from the AOS to the intake plenum. There are also two water lines that need to be removed. There will be some coolant that spills out so be ready with some rags. If the lines are original to the car don't loosen the separator yet as you may have to tug a little to get them off.

Once the lines are separated and you have cleaned up any spilled coolant, you can remove the AOS. Reach in from the right side where it is mounted to a bracket by two T20 torx screws. After you have removed the screws you just wiggle the AOS up and out of its bracket. Move the AOS aside and remove the two T30 Torx screws holding the bracket to the engine. You will not be able to fully remove the bracket because it is secured by the air conditioning compressor mounting spacer, but with the screws removed you will be able to swing it out of the way. This will give you plenty of room to remove and reinstall the Air Oil Separator. Keep an eye on how much coolant spilled and make sure to check your coolant level when finished to top it up.

(1998-2008 Common procedures)

Shown here is a new oil separator for the (Picture 2005:) 996 and first year 997.
Figure 1

Shown here is a new oil separator for the (Picture 2005:) 996 and first year 997. Lower left insert is the Picture 2008: AOS.

Open the engine decklid and remove the airbox.
Figure 2

Open the engine decklid and remove the airbox. Begin by loosening the hose clamp holding the boot to the throttle body (green arrow), then squeeze the tabs on the MAF connector to release it (yellow arrows). Now open the harness holder clip (purple arrow). Pull the oil filler tub up and out of its clip on the airbox. (blue arrow) and finally unbolt the 13mm bolt holding the airbox inside the engine compartment (red arrow) and carefully lift the airbox out of the car.

Remove the four 10mm bolts (green arrows) and also the 10mm nut (purple arrow) holding the throttle body to the engine.
Figure 3

Remove the four 10mm bolts (green arrows) and also the 10mm nut (purple arrow) holding the throttle body to the engine. At the same time, also remove the electrical connector going to the throttle position sensor (yellow arrow).

If you have an early car with a throttle cable, rotate the throttle back enough to relieve tension on the throttle cable and slip it out of the plastic cable cam as shown here.
Figure 4

If you have an early car with a throttle cable, rotate the throttle back enough to relieve tension on the throttle cable and slip it out of the plastic cable cam as shown here.

(Older cars only) Rotate the throttle body over to access the hose connection on the backside.
Figure 5

(Older cars only) Rotate the throttle body over to access the hose connection on the backside. On the older cars use a pair of pliers to loosen and remove the hose clamp holding the hose onto the throttle body. Don't forget to pull the O-ring out of the intake plenum that seals the throttle body to it.

(Older cars only) Follow the hose connection coming off the throttle body back to the control solenoid and press the wire piece in to release the electrical connector.
Figure 6

(Older cars only) Follow the hose connection coming off the throttle body back to the control solenoid and press the wire piece in to release the electrical connector. Now place the hose/solenoid assembly off to the side.

Once the throttle body is removed, you'll need to remove the intake plenums.
Figure 7

Once the throttle body is removed, you'll need to remove the intake plenums. Begin by removing the air hose connection to the oil separator. Squeeze the black plastic connector (purple arrow) to disconnect the hose from the plenum. Once free, set the hose connection aside. Now loosen the hose clamps securing the plenum to each manifold (green arrows). A good idea here is to loosen the inner hose clamps first and then rotate the plenum to help break the seal that may have formed between the rubber, then tighten the inner and loosen the outer clamps and do the same to break the connection between the rubber seals and the intake manifolds. Sometimes they can stick together making removal a bit difficult and this will help free them up. As you will note there is not much room to work and anything that makes it easier will help.

Once the hose clamps are loose, you should be able to push the intake seals onto the plenum, then slide the plenum over to one side and pull it free of the manifold as shown here.
Figure 8

Once the hose clamps are loose, you should be able to push the intake seals onto the plenum, then slide the plenum over to one side and pull it free of the manifold as shown here. (Picture 2005: Carreras only)

Now remove the rear intake plenum tube.
Figure 9

Now remove the rear intake plenum tube. Like the front one, loosen the hose clamps, then push the plenum over to one side. Once removed, pull the vacuum hose off the connection to the resonance flap inside the rear plenum. The idea here is to gain as much space as possible inside the engine bay.

Remove the two 8mm screws holding the hose connection to the left intake manifold.
Figure 10

Remove the two 8mm screws holding the hose connection to the left intake manifold. These screws also hold the retaining plate for the vacuum solenoid shown here just to the left. Once free, maneuver the hose, plate and solenoid up and out of the way.

Now it's time to remove the left intake manifold.
Figure 11

Now it's time to remove the left intake manifold. In thisPicture, we have a 996 engine out of the car to show the location of the six Torx bolts that hold the manifold to the engine (green arrows)

As you can see here, clearance is the biggest problem with removing the bolts that hold the intake manifold to the engine.
Figure 12

As you can see here, clearance is the biggest problem with removing the bolts that hold the intake manifold to the engine. In thisPicture, you can see that the coolant tank has been removed to provide even more access to the manifold bolts (Pelican Technical Article: Coolant Tank Replacement - Porsche 911 Carrera). The key here is patience. I've found that a combination of U-joints and extensions help out quite a bit when removing the bolts. Take your time and you should be able to get all of them out.

Be sure to remember to set aside the bracket at the front of the intake manifold.
Figure 13

Be sure to remember to set aside the bracket at the front of the intake manifold. This is one of those little things that is easy to forget when re-assembling the motor.

With all the bolts removed, carefully maneuver the intake manifold out from under the fuel lines and wiring harness.
Figure 14

With all the bolts removed, carefully maneuver the intake manifold out from under the fuel lines and wiring harness. As soon as you get the manifold out, be sure to stuff some rags or paper towels into the cylinder heads to prevent any dirt or loose objects from falling in.

With the intake manifold removed you now have access to the oil separator at the very back of the engine.
Figure 15

With the intake manifold removed you now have access to the oil separator at the very back of the engine.

Squeeze the connector on the upper part of the oil separator to release the hose connection as shown here.
Figure 16

Squeeze the connector on the upper part of the oil separator to release the hose connection as shown here.

Now, support the car on jackstands and climb underneath the car.
Figure 17

Now, support the car on jackstands and climb underneath the car. In thisPicture you can see the oil separator (green arrow) as it bolts to the side of the engine case near the transmission (red arrow). Begin by removing the hose clamp holding the rubber bellows to the bottom of the oil separator and pull it off. Next, squeeze the quick disconnect fitting on the vacuum hose (purple arrow) to remove it from the oil separator. The final step is to remove the two 13mm bolts holding the separator to the engine case (yellow arrows). (Picture 2008: Carreras only: This work was preformed on a crate engine we had at Pelican, to better show the location of everything, but can be done easily with the engine in the car)

For the later cars with the newer style AOS you will need to remove the both the power steering reservoir and the air conditioning compressor with its lines attached.
Figure 18

For the later cars with the newer style AOS you will need to remove the both the power steering reservoir and the air conditioning compressor with its lines attached. To do this you will first have to remove the accessories belt. To release the tension on the belt attach a 24mm socket to a breaker bar, place it on the idler arm and turn it clockwise (see Pelican Technical Article: Replacing Belts on the Porsche 911 Carrera). To remove the power steering pump first use a fluid pump or turkey baster to suck out as much power steering fluid as possible. Once the reservoir is empty, remove the 10mm nut securing the reservoir to the bracket (yellow arrow), then rotate the bayonet lock tab counter-clockwise to remove the power steering fluid reservoir from the car. The compressor is held in place by three long 13mm bolts. Remove the two front bolts along the front edge (red arrows). In order to get to the remaining a/c compressor mounting bolt, you'll first need to remove the temperature sensor mounted in the right (passenger) side manifold, in between the first set of runners (blue arrow). The sensor sits in a rubber sleeve that fits into a groove on the intake manifold. It's difficult to see it, but it will slide out. You can now access the remaining compressor bolt from in between the intake manifold (purple arrow). You'll need a combination of extensions and U joints. This bolt needs to be held in its upward position to remove the compressor. Once the compressor is free, unplug the electrical ground connector (green arrow), lay down a rag or towel to protect the paint of the car and lay the compressor off to the side of the engine.

Here is the AOS with the power steering reservoir and first intake plenum removed (the a/c compressor is still in place).
Figure 19

Here is the AOS with the power steering reservoir and first intake plenum removed (the a/c compressor is still in place). You can see the three vacuum lines (red arrows) and the two water lines (blue arrows) that need to be removed. Just push in on the blue clip and slide the water lines off. There will be a little coolant that spills out when you remove the water lines, keep an eye on approximately how much spills so you will have an idea of how much to replace later. The AOS sits in a tube that connects directly to the crankcase, be sure to clean up all the coolant before removing the AOS so nothing can get into the case. The green arrow shows where the power steering reservoir was connected.

ThisPicture shows the Air Oil Separator with the air conditioner compressor removed.
Figure 20

ThisPicture shows the Air Oil Separator with the air conditioner compressor removed. If you are working on your earlier car and happen to be reading this to see the difference, you might be a little jealous at how much easier it is to remove on the later models. The AOS is shown by the red arrow, while the yellow arrows show where the bolts that hold the a/c compressor go.

The AOS has been removed from, but is sitting on its mount in thisPicture.
Figure 21

The AOS has been removed from, but is sitting on its mount in thisPicture. The blue arrow shows the opening to the crank where it sits. Make sure to place a clean rag in here so nothing can get into the crankcase while you are working. The two T20 Torx screws that hold the AOS to the mount (yellow arrows) and the two T30 Torx screws (red arrows) that hold the mount to the engine case have been removed. You do not need to remove these screws if you have removed the second plenum as there will be room to remove the AOS from the top of the engine. Upper left insert is the air oil separator.

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Comments and Suggestions:
k8atu Comments: Question for you - If the engine is out anyway having a tranny rebuilt MY99 996 Tip Cab then would the AOS job still be a 5/6/7hour job? would imagine not, but the shop just quoted me 6 hours to do that work even with the engine out of the car? TIA Pelican!
November 29, 2016
  Followup from the Pelican Staff: No. Then it would be much shorter. Maybe an hour. - Nick at Pelican Parts  
Jetman Comments: Ordered and replaced an AOS from Pelican parts approximately 2 months ago due to excessive smoke on acceleration. Oil residue was excessive in the entire intake system. 8-12 hour job removing it from the top, cleaning everything out and reinstalling the new parts including the AOS vent tubing, top and bottom. Well just drove it today and it's smoking excessively again. Very frustrated. Is this a sign of a defective external AOS or could the internal AOS'S be bad as well? It's also leaking oil from the bellows again and running down the front LH side of motor after replacing it with new parts and clamps. I've driven the vehicle approximately 400-500 miles since the AOS was replaced. All was fine through high revs and normal driving until today. As soon as I hit 5000 rpms, the problem returned. Literally looks like something out of James Bond movie. As soon as I let off the accelerator pedal, smoking subsided and continued driving for another 10 miles with no re-occurence. No oil residue or carbon buildup on the exhaust tips as before. Very puzzling. How often do the internal AOS's go bad? Or could it be that I have just installed a defective new AOS?
November 18, 2016
  Followup from the Pelican Staff: if after a turn this can be normal under hard acceleration. if happened when driving normal, could be a fault or failing AOS, again. Unfortunately. - Nick at Pelican Parts  
Jetman Comments: Ordered and replaced an AOS from Pelican parts approximately 2 months ago due to excessive smoke on acceleration. Oil residue was excessive in the entire intake system. 8-12 hour job removing it from the top, cleaning everything out and reinstalling the new parts including the AOS vent tubing, top and bottom. Well just drove it today and it's smoking excessively again. Very frustrated. Is this a sign of a defective external AOS or could the internal AOS'S be bad as well? It's also leaking oil from the bellows again and running down the front LH side of motor after replacing it with new parts and OEM clamps. Any info would be appreciated!
November 18, 2016
  Followup from the Pelican Staff: When you say drove it again, are you driving it regularly? If not driven a ton after replacing the aos, it may smoke for a while until it is all clear. - Nick at Pelican Parts  
Martin Comments: I just had what looked like a major engine failure, first a small amount of blue smoke, then when coming off the throttle massive amounts of white smoke. All the plugs were very oily and two cylinders had a cup full of oil in themfront right and rear left. Is this symptomatic of an AOS failure or should I also be looking elsewhere?
November 16, 2016
  Followup from the Pelican Staff: Could be, check the plugs for oil to confirm. White smoke is likely coolant. I would pressure test the cooling system. If the system will not hold pressure and there are no external leaks the head gasket may be faulty.
- Nick at Pelican Parts
 
Stephan_Porsche Comments: Replaced mine on my 2005 Carrera S 3.8L, took 4-hours from start to finish including a coffee break. Job was a lot easier then others online say it is, I also read and was told it would be 8-14 hours, I would have to remove Intake Manifold and Fuel Rail. I didn't even have to remove the P/S Pump, with the AC Compressor out of the way the AOS comes right out with no problem.
November 13, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
jtrpin Comments: You state app 3 hr job. My Porsche mechanic advised that it would be 9 hrs, the extra time due to the collector tube which you do not mention. He states this is involved with every one that he does. Would like your input before I decide to go elsewhere. Thanks
October 27, 2016
  Followup from the Pelican Staff: Collection tube? Can you expand on what and where they said that is. - Nick at Pelican Parts  
Brien Comments: Is it normal operating procedure to remove the alternator when replacing AOS and is it common that the brackets break on 02 Carrera
October 25, 2016
  Followup from the Pelican Staff: Not common that it breaks. The alt coming out, it makes life easier when working inside the engine bay.- Nick at Pelican Parts  
Steve Comments: I began following this article to replace the AOS on my 2006 911 C2. Since it's separated out for 1998-2005 and 2006-2008 models, I followed the latter set of instructions for my car. After removing the power steering reservoir and AC compressor and finding the AOS to be nowhere in sight, I located the AOS straight back behind the driver's side intake manifold. Going back to the instructions for 1998-2005 cars, I'm seeing some differences as well. There seem to be only 4 Torx bolts securing the intake manifold-not the 6 stated in these instructions. Is my MY2006 car some strange combination of the old and new component locations?
October 17, 2016
  Followup from the Pelican Staff: It depends on the engine code, possible you have the older one in a newer vehicle. Which would make it seem off a bit. - Nick at Pelican Parts  
Hella-Buggin Comments: I'm reading a thread related to AOS failure and I see that someone posted a question that exactly describes my situation. MikeC4, in the comments section here:
http://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/09-ENGINE-Air_Oil_Separator/09-ENGINE-Air_Oil_Separator.htm

Is there anyway to put me in contact with him to see if and how he resolved it?
June 12, 2016
  Followup from the Pelican Staff: Unfortunately not. You may need the motorsport part as well. - Nick at Pelican Parts  
RJ Comments: thanks nick didn't realize cap locks were on when I typed that.it looked like I was yelling!haha
February 11, 2016
  Followup from the Pelican Staff: No problem. I assumed so. :) - Nick at Pelican Parts  
RJ Comments: JUST CHANGED AIR OIL SEPERATOR ON A CUSTOMERS CAR. CHANGED OIL FIRED IT UP... STILL HAS SMOKE ON START UP... HAVENT CHECKED WITH MANOMETER BUT THERE IS STILL SUCKING WHEN TAKING OIL CAP OFF BUT OIL CAP IS NOT HARD TO GET OFF. COULD IT POSSIBLY BE BAD AIR OIL SEPERATOR?
February 9, 2016
  Followup from the Pelican Staff: Could be, or residual oil, which is very common. - Nick at Pelican Parts  
911flat6er Comments: Any DIY suggestions for AOS replacement on 1987 3.2 911?
Heard it's any engine removal job!!!!!!!
December 8, 2015
  Followup from the Pelican Staff: I recall that being the case. It is mounted tot he rear of the engine crankcase, so difficult to reach otherwise. - Nick at Pelican Parts  
Aicedo Comments: I took my Carrera to a Porsche dealership because it was leaking coolant/antifreeze and I couldn't find the leak. They told me I needed to replace the AOS. Is this a symptom of AOS failure, or do I need to get a different diagnosis?
November 12, 2015
  Followup from the Pelican Staff: Yes, some AOS units have coolant lines. - Nick at Pelican Parts  
Hurdigurdiman Comments: as a PM move on my part, is there a rough estimate in mileage when the AOS goes bad? Say for instance as with the water pump going bad around 70,000 miles. My car has 76000 miles her now. No signs of a failing AOS as yet. Thanks for your reply.
September 23, 2015
  Followup from the Pelican Staff: Maybe at 100k replace it. Other than that, some last way longer than others. - Nick at Pelican Parts  
MikeC4 Comments: Hey there, I had the AOS symptoms, replaced it everything looked great no more smoking, until I did about 6 hard laps on a local track and then the symptoms reappeared.
I stopped my lapping day, and headed home the smoke was gone about 2 miles down the road and has not smoked again.
When I take the oil filler cap off I hear the sucking noise again now.
Can the AOS fail that quickly again?
Should I have used a performance oriented AOS?
Thanks
August 9, 2015
  Followup from the Pelican Staff: I can't imagine it would fail so quickly. If you are tracking the car, I would suggest the motorsports AOS. - Nick at Pelican Parts  
FastFrank Comments: Nick, spot on, on the problem. My 2003 C4S spent 1.5 yrs in the garage because I thought I needed a new engine 168K miles- blowing white smoke. Live away from civilization Lancaster CA and finally had the $$ to get it fixed. Took it all the way to Newport Beach to a fantastic P-car Mech. He called me up and told me that I had a $1600 bill replaced the coolant tank as well instead of a $18K bill which I had planned for. I did the happy dance for two days! I am putting a new clutch, motor mounts, RMS and upgrading the dreaded IMS Bearing as well. So Happy!!!
July 13, 2015
  Followup from the Pelican Staff: Awesome. Thanks for the note. - Nick at Pelican Parts  
whm Comments: My 2006 c2 has some white smoke on start up,but nothing after. Any ideas?
June 22, 2015
  Followup from the Pelican Staff: Make sure your car is not overfilled with engine oil. Could be the air oil separator. Take a look at your intake and if it is seeping engine oil, that is another sign that your AOS could be failing. Of course the definitive test is to check the crankcase vacuum on cold start. Should be pretty solid at 5" of water. - Casey at Pelican Parts  
iditude Comments: I have none of those models of AOS on my car 2004 3.6 C4 996 I have this one : http://www.pelicanparts.com/cgi-bin/ksearch/PEL_search_2014.cgi?command=show_part_page&please_wait=N&SUPERCAT_FLAG=Y&make=POR&model=5077§ion=engoil&page=6&bookmark=23&part_number=996-107-926-00-M100

Can you advise where it is located and the process to change it? I "think" it is the same as the old ones, but I am not sure.

Thanks for helping
June 14, 2015
  Followup from the Pelican Staff: I feel like I keep answering this but it doesn't post! The replacement is VERY similar as long as this style AOS is already installed it is plug and play. - Casey at Pelican Parts  
adam Comments: Just changed the oil air separator on my 996 carrera 1999. Car was runing before hand, but now it wont run. Its tries to fired up but backfires and stops? Any ideas?
June 13, 2015
  Followup from the Pelican Staff: I have made this mistake before. Double check the accordion boot VERY closely. If it is not completely seated it will cause the car to do that. Also double check the other connections bit they don't usually cause that problem. - Casey at Pelican Parts  
Chris Comments: Good morning Nick,

I'm going to replace my oil separator as well but on Fig 12 are u using a 1/4" or 3/8" socket?

Thanks and your article is excellent!

CHris KSA
April 19, 2015
  Followup from the Pelican Staff: 1/4" drive. - Nick at Pelican Parts  
Randy Comments: Not sure if the AOS or Valve seals causing my '02 911 turbo to smoke blue smokeIt happens on acceleration, and then disappear, the idle speed also goes up and down when parked. If The AOS is the culprit, please give some info on this particular model. Thanks.
April 3, 2015
  Followup from the Pelican Staff: Could be a faulty oil separator or the level is too high. You can test crankcase pressure using a manometer. - Nick at Pelican Parts  
Paul Comments: I recently replaced oil separator on my 2008 911 with 3.6L engine. According to this article, my was supposed to be behind AC compressor. After removing it I realized its not there, it was on driver side by the firewall. After removed driver side intake manifold which by the way was real pain, 1 bolt was just close to impossible to reach, took me 2 hours, I found out that bolt holding AOS are on the top of the engine, not on the bottom like the article says.
So, my point is this acticle is not correct at all. My buddy got 05 carrera with the same engine - AOS is located at the same location as on my car.
March 9, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
builder1 Comments: I am contemplating DIY this on my 2003 C4S. Not smoking yet, but I hear the whining noise. How much time will this take me.

Also, what parts do I need from Pelican here. I noticed an Oil Separator Internal and other parts. Thanks.
February 5, 2015
  Followup from the Pelican Staff: Should take about 3 hours.

The oil separator, the hose for the bottom of it. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need. - Nick at Pelican Parts
 
Zen 911 Comments: : I have a 2005 911 Carrera 997 3.6 . I started seeing left tail pipe smoke and black residue on the pipe plus hearing a knocking or ticking noise but car full of oil. I only have the car for a year it was my dream car and a birthday gift to myself. The car drives strong just in shifting gears you see smoke come out of left tail pipe. I took it to Porsche and they wanted to put a new engine in 30k expected I then took it to another mechanic and he attached a reader and discovered cylinder 3456 was bad and he didn't detect any metal in the oil so he recommended changing the Pistons. 7k : He stated its not a bottom end issue. So I was waiting for taxes to attempt the repair..then one day after adding oil to the car I took it for a spin and started to see the engine light start blinking and right a few miles it started losing power. I pulled over and googled the warning light and it instructed me to get it home immediately. Then driving home it started smoking really bad. Now when I start it up the engine light flashes and its smoking very bad . Just need some direction , I see the piece about the oil separator . Love the car . The I found another mechanic in NJ said he would do a top engine rebuild for 6k I was supposed to me this guy at the Maryland house and he stood me up and I had it towed there then had to return home with vehicle in tow .. : ... a friend that's a fellow Porsche owner recommended this site for honest help! I live in Maryland near Washington DC
January 31, 2015
  Followup from the Pelican Staff: First I would figure out where the smoke is coming from. Is the coolant level ok? You mentioned the oil level is Ok. If you have smoke, one of your engine fluids is leaking into the cylinder. Start there, then follow up with me. - Nick at Pelican Parts  
hobbitalan Comments: Just read the article my 1998 911 996 c2 tiptronic makes this squeal and I have ordered a new AOS which I will change out. Is there any other parts required for this task, also do I need to remove both intake manifolds or just the left hand side. My car also leaks oil from the bell house area which I am told is the crank seal will the AOS replacement make any difference to the leak and is it ok to run the car with this minor leak.
Many Thanks.
October 7, 2014
  Followup from the Pelican Staff: Just remove what is described in the article. As far as a parts kit, give our parts specialists a call at 1-888-280-7799. They can help you find the right parts.
- Nick at Pelican Parts
 
Tom W Comments: Hi,
I have a 2002 996 with a Tipp Trans. Are the steps the same as in the article to remove the AOS.

Thanks,
Tom
September 10, 2014
  Followup from the Pelican Staff: It should be similar, I can;t recall any major differences. - Nick at Pelican Parts  
Dave Comments: Gone through the article. Very good. Hoping to eliminate smoke after HPDE events. May consider the motorsport separator #996-107-926-00-M100. Is it worth 3x $'s an does it work? Please share unique install requirements and additional parts, if any. 2002 996 C4S application. Thank you.
July 26, 2014
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
levdeb Comments: Was able to get it all figured out. Thanks for the writeup!
June 10, 2014
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
levdeb Comments: Well, got all the way to the "get under the car" part, and its a different world. My AOS looks like the one in the photo I've attached. Nothing under the car looks like the photos you have. Not sure where I've messed up! 2003 C4 Cab auto...
June 10, 2014
  Followup from the Pelican Staff: It still attaches to the engine the same way. Look on the left side of the engine, near firewall. - Nick at Pelican Parts  

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