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I have seen the part (or parts rather - is it true there are two AOS, one for each bank? How do you know which one should be changed?
The AOS is located on the drivers side cylinder bank. Fairly easy to to change out yourself (20-30mins) only a T27 torx required if my memory serves correctly. Be aware, your best bet is to buy the whole assembly/cover with AOS built in, it is possible to buy just the rubber diaphragm which is likely the only faulty part, but Porsche no longer supplies them on their own so you need to source one from Russia, took me 2 weeks with expedited shipping and it did not fit properly, just a hair too small in diameter allowing air to leak past same as a tear would. Save yourself time and money by replacing the whole part.
Good morning All, New member to this awesome site. I am in the middle of the 2008 Cayenne Turbo (144,400 miles) Blue Smoke during downhill and highway decel then partial accel with the 2 to 3 seconds blue smoke in the rear view. Yesterday i removed the 2 rubber intake flex tubes, held on by hose clamps, that feed IC outlet air to the Intake Manifold via the Y pipe. The driver side (US orientation) was wet with oil pooling. I removed the driver side AOS chamber, it was fine, normally lightly wet with oil. I did find what i think is the problem, the Crankcase Bleed Vent Line (the 3 tip black plastic flex tube assembly that sits elevated across the top of the back of the engine towards the firewall, and connects to the 2 AOS chambers, part number 94810724553) PHOTO attached below, has a black plastic tube that runs perpendicular from that tubing assembly and drops down to the main Vacuum line that passes across the back of the engine. The white plastic T-fitting that's part of this factory part, the T-fitting portion that feeds this AOS vent line breaks due to age and heat, and causes a Vacuum leak. From what i can tell, this Vacuum leak would take away from the required Engine Vacuum causing operation problems with the AOS system.
The oil in the intake piping feeding the driver side of the engine is the lack of pooling we normally find in the Drivers Side IC hose from the turbo discharge, my IC hose was clear, contained oil residue, no pooling after 4000 miles on the oil, not normal, i should have seen some pooling. This told me that the oil instead of being retained in the bottom of the IC with normal closed system vacuum, this vacuum leak was allowing the engine to suck this oil into the engine, the oil was traveling vertical thru the IC from the bottom up, with the air flow, where it should be air only. Again, i have to point the blame for now on the broken vacuum fitting. I fixed it for now using a red electrical splice (double crimp) connector, its rigid and its a good tight fit in the broken T-fitting ports. I had the same problem on the 06 Cayenne Turbo S with the broken T-fitting and this red splice connector fixed it. The 06 did not show any oil smoke at all, i just found the leak at the time i was replacing the failed Coolant T-pipe at home and had the entire intake distributor off and just doing a good thorough visual inspection due to age and mileage.
And in the colder weather i noticed an engine valve tap, not the fuel injector orchestra, a real valve tap. I will monitor and report on that as well.
This blue smoke issue did also provide an increase in oil consumption, about 30 to 40% more oil consumption.
I will keep this board posted with my progress for the overall solution.
Thanks.
The little white plastic T-fitting breaks at the portion of the T where it enters the Black tube for the 3 port main vent line. my observation.
Good morning All, New member to this awesome site. I am in the middle of the 2008 Cayenne Turbo (144,400 miles) Blue Smoke during downhill and highway decel then partial accel with the 2 to 3 seconds blue smoke in the rear view. Yesterday i removed the 2 rubber intake flex tubes, held on by hose clamps, that feed IC outlet air to the Intake Manifold via the Y pipe. The driver side (US orientation) was wet with oil pooling. I removed the driver side AOS chamber, it was fine, normally lightly wet with oil. I did find what i think is the problem, the Crankcase Bleed Vent Line (the 3 tip black plastic flex tube assembly that sits elevated across the top of the back of the engine towards the firewall, and connects to the 2 AOS chambers, part number 94810724553) PHOTO attached below, has a black plastic tube that runs perpendicular from that tubing assembly and drops down to the main Vacuum line that passes across the back of the engine. The white plastic T-fitting that's part of this factory part, the T-fitting portion that feeds this AOS vent line breaks due to age and heat, and causes a Vacuum leak. From what i can tell, this Vacuum leak would take away from the required Engine Vacuum causing operation problems with the AOS system.
The oil in the intake piping feeding the driver side of the engine is the lack of pooling we normally find in the Drivers Side IC hose from the turbo discharge, my IC hose was clear, contained oil residue, no pooling after 4000 miles on the oil, not normal, i should have seen some pooling. This told me that the oil instead of being retained in the bottom of the IC with normal closed system vacuum, this vacuum leak was allowing the engine to suck this oil into the engine, the oil was traveling vertical thru the IC from the bottom up, with the air flow, where it should be air only. Again, i have to point the blame for now on the broken vacuum fitting. I fixed it for now using a red electrical splice (double crimp) connector, its rigid and its a good tight fit in the broken T-fitting ports. I had the same problem on the 06 Cayenne Turbo S with the broken T-fitting and this red splice connector fixed it. The 06 did not show any oil smoke at all, i just found the leak at the time i was replacing the failed Coolant T-pipe at home and had the entire intake distributor off and just doing a good thorough visual inspection due to age and mileage.
And in the colder weather i noticed an engine valve tap, not the fuel injector orchestra, a real valve tap. I will monitor and report on that as well.
This blue smoke issue did also provide an increase in oil consumption, about 30 to 40% more oil consumption.
I will keep this board posted with my progress for the overall solution.
Thanks.
The little white plastic T-fitting breaks at the portion of the T where it enters the Black tube for the 3 port main vent line. my observation.
Would this also cause intermittent idle increase too? I am also blowing tons of blue smoke on winding, mountain descents, with off-throttle decel. I'm burning close to a liter every 550 miles. AOS is brand new, PCV check valve is new... yet the consumption is driving me nuts. If there is one breather I have NOT replaced yet - it's that part you have pictured above....
Hello Dilberto, I am not the expert but we are all learning fast about these issues that just appear due to age and mileage. Yes, i noticed light surges in the idle while in Drive at a stop with the brake pedal applied, probably from the vacuum leak; that's normal for vacuum leaks with most engines. I run Regular Techron Fuel Injector Cleaner thru the system every 6 months, usually 2-16 oz bottles on a full tank of fresh premium (93 octane), and drive that tank full of fuel + cleaner down below a 1/4 tank to optimize the fuel system cleaning, get the fuel level as close to the "Please ReFuel" display indicator as possible.
The blue smoke you are seeing is most likely due to the oil being drawn in thru your fresh air intake, if you remove the 4 hose clamps and the 2 Y pipe flex hoses at the front of the engine, you will see the oil pooling and line of oil in the bottom of the hose at least on the drivers side hose and IC outlet tube feeding the Y pipe. Oil consumption is the life of these turbos, my normal oil consumption is 600 miles per quart, (using only Edge 5w40 since 2011, and its driven like its stolen constantly), now i'm at 400 to 450 miles maybe 500 on a good week. i have not driven yet since the repair work that i performed yesterday, but i did start the engine to make sure all was good with the reassembly and no Codes were being thrown. I did notice the engine was quieter after the repair. With this vac leak at the back of the engine, i had no codes at all for it or for any lean misfires; as sensitive as the Gen 2 computer system is, it has not presented any codes, using the Durametric and always the latest updates. I also pulled a spark plug and saw the light blue crust build-up during yesterdays repair work, it flaked off very easy when i checked the gap with the Ramp-style Gap tool.
Also the oil is dirtier and more worn than normal for having only 4000 miles on it, its got the same color, clarity and (nitrile gloved fingers with 3 to 4 dipstick drops of oil on the thumb and forefinger) the pinch and squeeze test as the 06 Cayenne Turbo S with 8000 miles on its engine oil. The Turbo S has about 144,100 miles total on it. Both oils still feel good when doing the pinch and squeeze test (my version of oil quality verification).
Can you tell me about the PCV check valve, maybe post a photo of it with a part number as i did for the T-fitting and a PCV check valve location, not sure if that's the Brass top check valve on the passenger side rear-of-the-cylinder-head vacuum pump. I would like to look at that also. I am also taking time this afternoon to see what i can find about the Porsche AOS technology and how vac and a lack of vac affects its function.
Another blue smoke indicator, If i park overnight with the front end pitched slightly downward from the vehicle horizontal, i get the 2 to 3 seconds of cold start blue smoke, more so from the drivers side tail pipe, normally half the smoke from the passengers side tailpipe. Also, Just cruising down the highway (Interstate 95), taking the foot off the gas pedal and lightly applying it, i get the rear cloud, more than i want to see.
Definitely the engine's internal vacuum and turbo pressure, drawing and forcing the oil vapor thru the IC system thru the Y-pipe and combusting it, hopefully this fixed vacuum leak fixes the problem.
I too ordered the new AOS diaphragm from Russia, Outside diameter was too small to provide the proper seal, and it screamed at me to let me know. The original diaphragm is still good, i verified it with a very thorough visual inspection, and no noises from it and the black cap during engine run time.
I was planning on driving it for a few days, give the system a chance to return to normal if this vac leak was the main cause of the problem, then i will report back either way with my findings. I am not seeing any other posts anywhere with this info, and as these Gen 2 Turbo Cayenne's continue to be driven and age, these problems are going to become more prevalent. That's why we are here discussing it now. Hope this all helps, it seems to be my complete experience so far with the blue smoke. Please keep us posted as well with all of your progress.
This is the 955 PCV check valve, which the L-bend inlet comes directly from the AOS. It's a one-way oil vapor conduit, allowing it to be burned, thru the intake. However, I'm suspecting the AOS is pulling straight oil at full boost, instead... possibly due to an undiagnosed vacuum leak, or valve cover gasket failure:
Thanks for the Photo. i attached my upgrade below.
I drove the 08 about 1 hour ago, the idle surging is gone, engine is smoother, quieter at idle, and accelerating. Still seeing some residual smoke as i did not clean the system, will take a few weeks to dry out the oil residue. on the 06 the Vacuum T-fitting is not visible without removing the rear upper plastic cover under the hood with the pushpins, and maybe the drivers side air pump. Also consider if you have had any maintenance performed by a garage and they removed the intake distributor, possibility of the new gaskets being over-torqued causing a vac leak and rough idle, that's what brought me to do my own Coolant T-pipe on the back of the engine at home.
Standard 1/2 inch copper tubing for home water supply, the gray paste is just an automotive gasket sealer, the 1/2 inch copper was an incredibly tight fit to begin, the sealant makes sure no leaks become present. Not paying $124 for a plastic tube that will fail again. Copper is the most readily available and the least reactive to most chemicals, at least engine oil and gasoline for this application.
Please keep me posted for when you work on the Vac T-fitting.
Thanks D! I'm kinda wondering if this item is going to be problem for me when 30lbs of boost put my crankcase pressure through the roof. I ordered from here because I'm in Tx and Klain is in OK. I would do buisness with them again in a heartbeat.
Thanks D! I'm kinda wondering if this item is going to be problem for me when 30lbs of boost put my crankcase pressure through the roof. I ordered from here because I'm in Tx and Klain is in OK. I would do buisness with them again in a heartbeat.
Do you know if this is this just a 4.8 issue or does it affect the 4.5 TT too? Mine hardly uses any oil at all but I want to keep it that way!
02-16-2018, 08:09 AM
