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Repairing the Air-Oil Separator
 
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Pelican Technical Article:

Repairing the Air-Oil Separator

Jared Fenton

Time:

1 hour1 hr

Tab:

$175

Talent:

**

Tools:

Pliers, flat-head screwdriver

Applicable Models:

Porsche 955 Cayenne (2008-10)
Porsche 955 Cayenne GTS (2008-10)
Porsche 955 Cayenne S (2008-10)
Porsche 955 Cayenne Turbo (2008-10)
Porsche 955 Cayenne Turbo S (2009-10)

Parts Required:

New diaphragm

Hot Tip:

Use caution when removing the separator cover

Performance Gain:

No more smoke or idle problems

Complementary Modification:

Replace crankcase breather hoses

The engine air-oil separator is an emissions device located on the top front corner of the right side valve cover. The separator 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, it causes an 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 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 hissing from the separator when it's running. This is caused by air being sucked in past the diaphragm seal. The air/oil separator is part #948-107-236-52-OEM. PLEASE NOTE: It is no longer possible to purchase the diaphragm as a separate part. You must replace the entire assembly as a kit. 

The first step is to open the hood and remove the front engine cover. See our article on Removing Engine Covers for more information.

Squeeze the tabs (green arrows) on the breather hose leading to the air-oil separator and pull it off.
Figure 1

Squeeze the tabs (green arrows) on the breather hose leading to the air-oil separator and pull it off.

Shown here is the air-oil separator with the hose removed.
Figure 2

Shown here is the air-oil separator with the hose removed. Note the tabs (green arrows) around the perimeter of the plastic cap. Also note the oil/dirt residue at the bottom of the cap (yellow arrow). This is an indication of a leak.

Use a flat head screwdriver to carefully pry the plastic cap over the tabs on the valve cover.
Figure 3

Use a flat head screwdriver to carefully pry the plastic cap over the tabs on the valve cover. Use caution and work slowly. You should be able to pull it off once you are about halfway around.

With the cap removed take note of the spring (green arrow) inside.
Figure 4

With the cap removed take note of the spring (green arrow) inside. Make sure you don't lose this.

Carefully pull the diaphragm out of the cap along with the support plate.
Figure 5

Carefully pull the diaphragm out of the cap along with the support plate.

Pull the support plate off the diaphragm.
Figure 6

Pull the support plate off the diaphragm. Note the way the plug on the diaphragm (green arrow) fits into the support plate (yellow arrow).

Shown here is the problem.
Figure 7

Shown here is the problem. The diaphragm tends to crack right along the edge where it seals against the separator cap (green arrow). Fit the new diaphragm into the support plate and then also into the cap. Make sure that the spring is located correctly into the separator and then place the cap over and down until it locks. Press the air hose back onto the separator and you're good to go.

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Comments and Suggestions:
Mike Comments: Engine light came on . # 5 cylinder- coil area full of oil. Plug looked very gummed up.
Replaced both valve gaskets, coil, spark plug. All the other plugs like oily and rich. The oil separator looks good.
Should I replace the o2 sensors?
November 28, 2016
  Followup from the Pelican Staff: No unless the engine was burning oil and contaminated the sensors. - Nick at Pelican Parts  
grossman26 Comments: What is the oil air separator part for 3.6l 2008 Cayenne?
October 20, 2016
  Followup from the Pelican Staff: Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
ForrestForever Comments: Please note that the air/oil diaphragm orange colored disc part in the pictures is NOT the same for the 4.5l and the 4.8l engines. The repair steps shown here are very similar except the 4.8l engine has an fused diaphragm with the hard center core built into the rubber diaphragm.

June 20, 2016
  Followup from the Pelican Staff: - Nick at Pelican Parts  
CayenneSS Comments: For those looking for just the membrane without the valve cover. Can Pelican stock this part? Seems like a popular issue. http://vanos-bmw.com/diaphragm-valve-for-crankcase-ventilation-porsche-cayenne-4-8l-m48-01-m48-51
March 17, 2016
  Followup from the Pelican Staff: I will suggest it be added to the catalog. - Nick at Pelican Parts  
vincie Comments: i need a diaphragm it looks like, to fix my idle and hissing sound problem on my base cayenne 08, and when I try to click the order it's not going anywhere
December 27, 2015
  Followup from the Pelican Staff: I’m not the best with part numbers.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
theWerkstatt Comments: Can you supply the full repair kit?
November 3, 2015
  Followup from the Pelican Staff: Yes. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Raden Comments: My 2009 GTS just developed a small crack in the diaphragm which was causing a rough idle, squealing like it was a fan belt and hissing from the AOS. The crack was small enough, so I taped it with heavy duty 3M tape and it fixed the problem. I know it's a temporary fix til I receive my new diaphragm from vanos-bmw since Bruce at Pelicanparts told me that I needed to order the whole AOS which I don't need. BTW, if you try my fix, you need to tape it from behind so the tape is in between the diaphragm and the black cap.
August 28, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
SemperPorsche Comments: Pelican does not sell the diaphragm by itself, you have to buy the entire oil/air separator. Anyone want to mass produce a shit load of these and open a company with me? This seems to be a VERY common occurrence and you shouldn't have to buy a part for $175 when all you need is the rubber diaphragm inside for $10, and thats even a 1000% markup.
August 20, 2015
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help. - Nick at Pelican Parts  
Riyadh Comments: so any of you guys able to buy the diaphragm not the entire cover? where and what's the part number for a 955 2006 base model
July 28, 2015
  Followup from the Pelican Staff: We should have a kit for you.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Abdul Comments: how many oil separator valves do i need for my 2009 cayenne S V8 4.8 L engine?

thx
July 28, 2015
  Followup from the Pelican Staff: There is one valve, but both covers are part of the system.- Nick at Pelican Parts  
Glenn at Pelican Parts Comments: I'd like to summarize/update this article. The only way I know of to get the needed part at this time is to buy the entire valve cover. It's part number 94810513107.Part number 94810743750 is not it. That for the seals that go under each corner of the valve cover. Part number 94810593400 is not it either. That's the gasket for the cap on the valve cover. The only place I've heard of that offers the diaphragm is a mystery company in Russia. I don't know what company nor do I know what part number is used with that company, sorry!
July 24, 2015
  Followup from the Pelican Staff: Glenn is on it! - Nick at Pelican Parts  
rich Comments: took 3 weeks from russia for mine.
June 18, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
tcooper Comments: Alex, how long did it take to come in? Odd looking site. Some pages are in Russian.
May 27, 2015
  Followup from the Pelican Staff: Try google translate. - Nick at Pelican Parts  
Alex Comments: the number who gave Nick is for gaskets. not for the membrane.

I bought the membrane here
http://vanos-bmw.com/membrane-94810513107-porsche-cayenne-45l-450ps
May 22, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Jet Comments: 94810513107 part number is the entire Valve Cover with Crankcase vent.
April 23, 2015
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Ringnalda Comments: I think the partnumber for this membrane component is 94810513107. I paid $59 for it.

Hope this helps someone to save a lot of time.
March 24, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Ringnalda Comments: the part number in the article is actually the seal that goes around the electrical connection through the valve cover. Correct part number would be great.
March 16, 2015
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
Nickelless Comments: Hi I'm in the Netherlands
According to Porsche, it wasn't possible to order only the diaphragm, unfortunately I had to order a valve cover complete :-

Has someone the correct part number only for the diaphragm?
February 5, 2015
  Followup from the Pelican Staff: I don't think you can get just the diaphragm. Would the same here in US. - Nick at Pelican Parts  
RLHornbeck Comments: I am also looking for this part. Does anyone know the part number yet?
January 21, 2015
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
tcooper Comments: I started this mess, so I'll ask for an update. I've had no luck finding this part. :
January 20, 2015
  Followup from the Pelican Staff: Still no luck even with the part number? Did you try calling our parts specialists? - Nick at Pelican Parts  
Ben Comments: the part number listed is still incorrect. Can we please update the part number so i can order the part?
November 25, 2014
  Followup from the Pelican Staff: I will follow up with my team again. I believe it is on their to do list. - Nick at Pelican Parts  
CAS Comments: I am in Australia Nick, cant the parts team just post the correct part number?
November 12, 2014
  Followup from the Pelican Staff: OH! I will ask to email it to you. - Nick at Pelican Parts  
CAS Comments: The part number listed is still incorrect, could you please prove a link to the correct part. This is the seal below the rocker cover
November 11, 2014
  Followup from the Pelican Staff: I am not the best with part numbers, I do not have an application to look them up.

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
 
Sam Comments: I cannot seem to get a correct part number for an 04 Cayenne Turbo, can someone please advise.

Thanks
October 2, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part. - Nick at Pelican Parts  
tcooper Comments: In looking around the web, the 948 105 934 00 part number seems to be correct. YEA, Kris!! I'm going to order one and see. Wish me luck!
July 29, 2014
  Followup from the Pelican Staff: Let us know how it works out. - Nick at Pelican Parts  
Brain Comments: The 948 105 934 00 is the camshaft adjuster cap seal on the valve cover. I don't know where this replacement diaphragm is supposed to come from or what the part number is but as far as I can tell, they don't exist. The cap and diaphragm are only available with a new valve cover. If someone has information otherwise, please share.
July 17, 2014
  Followup from the Pelican Staff: I will have the article double checked to see if it is correct. for now, Give our parts specialists a call at 1-888-280-7799. They can help you find the right part. - Nick at Pelican Parts  
Kris Comments: Is it supposed to be 948 105 934 00? Because Pelican also sent me the wrong part.
July 17, 2014
  Followup from the Pelican Staff: I will have the article double checked to see if it is correct. for now, Give our parts specialists a call at 1-888-280-7799. They can help you find the right part. - Nick at Pelican Parts  
tcooper Comments: I wonder if it is the whole cap? I managed to stick the screwdriver thru it and put a hole in it. Now every time I crank it I get a plume of blue smoke out the exhaust.
July 16, 2014
  Followup from the Pelican Staff: You'll have to replace it if you punctured the diaphragm. - Nick at Pelican Parts  
Brain Comments: The part number 948-107-437-50 is not the correct part number for the diaphragm. That is for the seals that go under each corner of the valve cover.

I still can't find this part or the correct part number.
July 16, 2014
  Followup from the Pelican Staff: I will have the article double checked to see if it is correct. for now, Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts - Nick at Pelican Parts
 
tcooper Comments: Hi Nick, that part number does not seem to be correct. Can you verify? What I received doesn't look a thing like the photos. photo attached
July 15, 2014
  Followup from the Pelican Staff: I will have the artilce double checked to see if it is correct. for now, Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
tcooper Comments: The part number magically appeared in the article. NICE!
July 7, 2014
  Followup from the Pelican Staff: Thanks for the follow up. - Nick at Pelican Parts  
tcooper Comments: Looks easy enough, how about a link to the part? I cannot seem to find it.
July 5, 2014
  Followup from the Pelican Staff: The link on the article should have them, I will have it checked to see if it is working.

- Nick at Pelican Parts
 

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