jhasti

I have a 2005 Carrera S with 68,000 miles. I recently started having problems with a large white cloud appearing only at start-up and some poor throttle response at low rpms. I had also noticed for the last few months that the oil consumption seemed a faster than usual for my car. After a little reading I found that it might be due to the AOS. My Durametric program was giving some RKAT and misfire codes, but the check engine light (CEL) was not on - of course, after I checked the codes, the CEL came on. With the engine running, I tried to remove the oil filler cap but couldn't - I would have had to pry it off the tube. So it really did seem to the AOS. Apparently when the AOS goes bad, it causes a high vacuum in the crankcase (hence can't pull off the oil filler cap) and this pulls oil into the recirculation system that drains into the intakes (hence the white cloud at start-up and high oil consumption). I looked around and found some information on Rennlist discussing AOS replacement on a 996 (http://forums.rennli...labor-time.html). People discuss dropping the transmission or lowering the engine to help with this. I'm my case only removing the engine would have helped. The hose clamps are pointed towards the back of the car so I would not have been able to do this from the transmission side. You should know that the 997 S uses a different AOS than the non-S 997 or the 996. Based on all this information I ordered from Zim's (www.allzim.com) AOS for ~$150 3 intake gaskets (~$8) (didn't use these in the end) one throttle body gasket (~$7) as well as a new serpentine belt, and all three idler pulleys (pullies?) because I thought I would do this at the same time. Tools are shown and with some listed at the bottom. First, the pre-picture . Obviously I have a fabspeed cold air kit. The red color sticks out like a monkey-butt, but I like the sound. The AOS on the 997s is under the passenger side intake manifold about halfway to the front of the engine. So some things have to come off... the air box needs to come out, there is a good air filter replacement tutorial here on Renntech. This picture shows the air box partially out and rotated over so that you can see the connections. I also zoom in here just to show the vacuum connection on the solenoid, one of the electrical connections on the solenoid (already disconnected), and the mass air flow (MAF) sensor connector. Just ignore the broken wire clip. Some gremlin must have done that... Now the throttle body has to come off - there are four E-10 bolts, and the bottle left one has a bracket that hold a little rubber bumper attached to it. Only the four E-10 bolts need to come out. There is also an electrical connector at the top (runs from left to right) and if you squeeze it just right on a tuesday with a full moon, it will pop off. Here are two pictures of the throttle body off the car, note that there is oil on the inside and both the inside and outside need cleaning. Now to get the intake pipe out from between the left and right manifolds. You can see that there is the plastic Y splitter that the throttle body attaches two, and then two short rubber hoses that attch the plastic splitter to the intake manifolds. There is a recirculation hose connected to the top left of the splitter. The other end of this hose is connected to the AOS. Porsche was VERY nice when they made these hoses, if you squeeze the two textured parts together the hoses pull off easily - no wire hose clamps. Yeah Porsche! Also notice that this splitter piece has the groove where a new throttle body gasket should go. Each rubber hose has two large hose clamps on it. In order to get the splitter out, I recommend loosening only the two outer most clamps, that is the clamps on closes to each intake manifold, because then you can rotate the splitter up or down to help break the seal of the rubber hoses on the intakes. Then I removed the inner two clamps and broke the seal of the rubber hoses to the splitter. To get everything off, I pushed the rubber hoses as far onto the intake manifolds as I could (essentially pushing the two rubber hoses father apart) , and then the splitter came out from between the hoses. In retrospect - and after putting all this back together, I would have pushed the rubber hoses closer together onto the splitter and then taken out the splitter with the hoses attached as it went back on this way pretty easy. Here is the splitter And here is where the splitter was... In this last picture you can see the short rubber hose segments, the disconnected recirculation hose, and the back crossover tube that also connects the two intake manifolds. If you follow the disconnected recirculation hose down, you can see the top of the AOS. I could see that a fair amount of oil had collected in the intake system. I also removed the power steering reservoir - there is a 10mm bolt on the right side holding it to the right intake manifold and a plastic tub that connects down to the pump. That tube has a nice twist connector on it, twist it to the left (counterclockwise) about a quarter of a turn and the whole thing will just pull out. This picture shows where it was, and the black plastic tube that has a green o-ring is where that reservoir was connected. Now I removed the 4 E-10 bolts that held down the right intake manifold to the cylinder head. This is where things may have been easier on the non-S or the 996? My intake manifolds are one piece with the injectors attached to the bottom. There are 4 bolts, one on each end and one between each pair of cylinders. If we number them from rear of car to front, number two was the real pain to get out. There is a sensor embedded in the manifold directly above this bolt which made it difficult, but eventually the right combination of extensions and u-joint made it possible (it was harder to replace than to remove). I couldn't really get a good picture here. I couldn't easily figure out how to get the fuel supply line and injectors disconnected, so I couldn't pull out the intake. Removing the intake bolts did left me move it around some which was helpful, but I'm note sure it was actually necessary to get the AOS out. Also, since I couldn't get it off, I couldn't change the gaskets - so I'll keep my fingers crossed that the old gaskets are still in place. This picture shows that I've removed the old AOS - you can see the recirculation hoses that attach to it (there are three - two on the left and one on the back), and then two small coolant hoses (both on the left). What it doesn't show is that there are two small T20 screws that hold the AOS to a bracket on the cylinder head. See the diagram below for better idea. I sure hope your hands are any larger than mine... I used a T-20 bit and a small ratcheting monkey wrench to get to these. If I hadn't loosened the right intake manifold, then I'm not sure that I could have gotten my hand in there to do this. There are the two coolant hoses that have to come off, one of them come from the water pump and there is a small segemnt of it that is rubber with a spring clamp right at the water pump fitting. This picture shows where I'm talking about. In retrospect I don't think I had to take this off, but it was easy. Please ignore the broken oil-pipe filler. Who did that? Turns out that this filler just sticks out into space and it is really easy to put too much pressure on it with your arm when trying to work on the intake. It snaps with a nice crisp pop that reminds you of a broken bone. Turns out it is a $40 dollar part that has to be ordered and it looks like the alternator has to come off to replace it. I think I'll keep my serpentine belt and pulleys for a future weekend when I get to change the filler pipe. Also, here I want to show the water hose connection, again an excellent job by Porsche. The blue piece on the end of the hose is a tab, than when pushed releases the connection and the hose comes right off. I only lost about 1/ 4 cup of coolant when disconnecting both water hoses. Lastly, here is a picture of the space where the AOS was sitting. You can see the opening in to the crankcase where the bottom tube of the AOS fits. A little wiggling and the new one slides right in. I cleaned everything using a carb cleaner and P21 citrus cleaner. Now that everything is apart, it's time to put it together. 1. new AOS in, connecting coolant hoses first and then getting the t20 screws into the AOS from the right side of the engine. 2. connect recirculation hoses to the aos, and the coolant hose back to the water pump fitting. 3. reconnect the rear crossover tube by pushing the rubber hoses as far as possible onto the intakes - again this helped that my intake was loose (take special care to get the vacuum connection reattached - I had to disconnect this vacuum hose over on the left intake manifold so that I could get enough slack to work with it, once it was back on I reconnected the vacuum hose on the left intake manifold. 4. put the bolts back into the right intake manifold, I did each hand tight with a socket extension and then torqued each to 7.5 ft-lbs (this seems right) - I also had to reconnect the sensor connector over that #2 bolt. 5. then I adjusted the rear crossover tube and then tightened the hose clamps (not too tight). 6. Then I put the front intake splitter and rubber hoses back on, to do this I pushed the hoses all the way onto the splitter and fit it between the intake openings and then separated them onto the intakes. Worked pretty well. 7. lined everything up and tightened the hose clamps (not too tight). 8. connected the recirculation hose to the splitter 9. Replaced the power steering reservoir, twisted the pipe connection to lock and replace the bolt into the right intake manifold 10. put new gasket on the splitter to throttle body face. 11. put throttle body back on the splitter - (torqued these to 7.5 ft-lbs also) 12. replace the air box with the two electrical connections and the vacuum connection. (13. duct tape the crap out of the oil filler tube to hold it and seal the vacuum until I can replace it) I'll say, there is some satisfaction in knowing that part of my $100k car is held together with duct tape. I started the car and filled my garage with white smoke - there was still some oil in the system from the last time it was stopped, but the car idles lower, better low end response, and I can get the oil filler cap off without giving myself an aneurysm. The posts I've seen say that it will continue to smoke on start up until the oil is cleared out. Might have done differently: 1. Not sure if I had to take the intake manifold bolts out - I had hoped to remove it, but in the end I couldn't. 2. Probably would remove the belt, and alternator in order to take off the oil filler pipe and get it out of the way - that would have kept me from braking mine.. 3. and if I did #2 above, I would have changed the pulleys and belt at the same time. Time: about 7 hours split over two days, next time might take 5 hours. Tools: here is everything that I used. Note the diet coke, this was necessary in copious amounts. Lots of 1/4 and 3/8 inch extensions and adapters to make different lengths. 7mm, 10mm, and 13mm sockets. An E-10 star socket and a T-20 torx bit (or a star bit) I have both of these from a kit sold by harbor freight. Also came in handy when I changed the spark plugs and coils a year ago. The magnet and mirror are indispensable. I hope you have as much fun as I did. Someone described it like having your hand up a cow's backside, and there are times that made me chuckle. It is always nice to learn a little more about my car. I am in Dallas, and if anyone needs help or has questions, just let me know.