Identify this part!
 

I have a p0507 CEL with eratic iddle and a hiss from somewhere in the engine bay, I suspect the problem is a vacuum leak from some where after the air oil separator. If I disconnect the breather hose from the AOS and block it off the intake side, the hiss goes away and idle returns to normal. But then I am left with a puddle of oil under the drivers side. I suspect that the oil and vacuum leak are coming from where the AOS connects to the left head. I believe this is the part that connects the head to the hose leading to the AOS. It has a funny springed vent facing the camera and the whole part was covered with dirty oil. I'd like to know what the function of the spring mechanism is to see if I can just seal off the vent. I'd also like to know the name / part number of this head breather vent thing so I can replace it.

This picture shows the part looking at the engine from behind the drivers seat firewall cover removed (USA left hand drive) and is under the intake manifold.

Well it appears you are correct on all accounts. That is the crankcase breather/ AOS connection. PN is 996-107-047-51 to MY 02, and PN 996-107-047-00 for MY 03 and newer. Not easy to get to. #6 in parts diagram below. $17.25 new from Pelican.


http://986forum.com/forums/uploads02/AOS1472924649.jpg

Look familiar:

http://986forum.com/forums/uploads01...1432431884.jpg

It is your PCV valve.

Thanks. I just capped off the vent to see what would happen. Nothing seemed to change . The hiss was still there, maybe it's normal for the AOS to hiss. Before when I capped off the breather hose to the AOS The check engine light immediately went away. when I capped the vent it did not. Is the PCV a common failure spot, is the leaking from the pcv when it's not connected to the aos normal.

Just replace the damned thing, it is not that expensive.

I'm not worried about $22, and I appreciate your help, but I'd like to identify the problem. If i wait for a valve and 5 days later (with the holiday) it comes, I install it and then the problem continues, that was 5 more days the car is out of service.

In reading about the PCV valve I suppose the problem could be that it is stuck open. But when it leaks it's about 1/2 cup of oil which seems like a lot for a PCV.

Along with the p0507 a few days after this light comes on I get a cel for running lean.

Can someone confirm that a hiss from the AOS is normal, it does seem to function correcctly and I can't be sure where the hiss is coming from, but I don't think it's coming from the PCV. Concidering the function of the PCV I suppose it is normal for it to have oil collecting around it.

The AOS doses not normally hiss. You should be checking the vacuum level (in inches of water) at your oil fill cap. It should be steady at 5 inches, if it is lower, something is leaking, if it is higher, the AOS is shot.

I pulled the PCV and started the car, no difference. I covered the part of the valve that goes into the engine expecting a vacuum, there was none.

With it out I can see it's not like a traditional PCV, there is no inline mechanism for controlling the flow between the AOS and the head, it's wide open. Instead it's only purpose it to vent to the open air. I no longer think this will be the source of my problem. The lack of vacuum reaching the PCV is suspicious is it not?

The AOS is the pvc valve, there is a membrane inside that controls the flow with manifold vacuum.
A vacuum leak usually trigger P1128 and P1130 on a boxster.
Here the is a problem with idle control.
Do you have a 2.5L?

OK so with the PCV valve out and the tube in the open air, the car still leaks oil just like when I disconnect the PCV I can't say that I should be surprised but since vacuum is not reaching the PCV - I actually am a bit surprised. but now I can say that it IS NOT leaking from this area where the valve is.

Ben006, I have a 2000 Boxster S with egas. A vacuum leak is suspected somewhere after the AOS, but maybe the AOS itself is faulty. I've tried spraying MAF cleaner all around the AOS and it's connections to try to find a vacuum leak, but it did not hear an idle change, It does not mean it's not the problem. The whole oil leak issue is maybe distracting me from looking at the AOS more closely.

Oh, and P1128 and P1130 are the lean codes I get a day or two after I get the P0507.

Leaks oil from where ?

Reconnect everything and measure crankcase vacuum through the oil filler.
If you don't have a gauge accurate enough, make one:
http://nsa38.casimages.com/img/2016/...1720915710.jpg
This is a water column pressure gauge, one end is open to atmosphere and the other to the crankcase (it has to be air tight). You then look at how far the water level at multiply by two to have the pressure in In of water column (InWC).

It should be 4 to 6 InWC of vacuum.

What engine do you have?

It's the 3.2 stock motor for the 2000 boxster S

I did check the vacuum at the oil filler without a gauge and the vacuum was light.
I just now found the source of the oil leak, it's coming from drivers side spark plug hole closest to the firewall. I suppose that when I disconnect the hose it does not allow the crankcase to vent properly and is finding the weakest seal. This surprises me as thought it would be vented to the open air and have no pressure with it disconnected. Besides the hose did not seem to pull any vacuum anyway. Clearly I lack an understanding of how all this works. That spark plug tube was fine when I changed out the plugs a month ago.

I'll have to see about making a vacuum guage. Or maybe I can just pressurize the line from where I already have it disconnected and block off the airbox and listen for a leak

I do have the torque app that will tell me vacuum from the ODBII port, will this be accurate enough?

The vacuum in the crankcase is very small, not something you can judge by hear or feeling, you need a gauge.

Change the spark plug tube first then.

A part is always fine before it breaks ;)

For the code, try to clean the throttle body if you haven't!

I've cleaned the throttle body and MAF. I'll report back after I measure the vacuum from the oil filler.

That part is part of the pcv
It is a spring loaded valve that prevents your seals to blow if too much pressure in the cranckcase is present.

If you have a semi operational AOS and bad spark plug tube seals the car leaks little oil if you disconnect or cap the throttle body to AOS hose the car with bad spark plug tube seals will leak a lot of oil because there is no vacuum present in the crancase and the pressure builds up and leaks like crazy.

You have, I believe a combination of the following:
A) bad spark plug tube seals AND
B) bad or going bad AOS diagragm (hissing)

Or
A) bad spark plug tube seals AND
B) vacuum leak

Vacuum leaks can be found at
-hose from drivers side vent valve to aos
-aos itself
-hose from aos to throttle body
-aos bottom bellow
-dipstick tube
-oil fill tube
-little hoses that go inserted into intake bellows
- little hose that connects to throttle body
- throttle body boots

Changing the spark plug tubes or/seals will stop the leak, replacing the AOS and/or finding the vacuum leak will stop the hissing noise and will fix your rough idle.

It is possible that your AOS is going bad and is creating excessive vacuum (negative pressure) in the crankcase and the hissing noise is actually air sucking thru the bad spark plug tube seals.

So I would replace all spark plug tube seals firts and go from there

I have some very sensitive manometers. Glad to help when I'm back in town if you're in SLC area. I can check very low vac or positive pressure in inches of WC.