Weeping AOS line?

Hey all, Was under my car today checking the engine mount sag (which looked in good condition) when I noticed a corrugated hose that was damp/leaking with oil. No drips just looks like it's weeping, is this the crankcase breather line for the right side of the engine? First pic is under the engine on the left side. Car is a 2004 C2 83kms. Is it easy to replace? It looks like it weavs its way through the engine so it doesn't look easy. As well as the fact that it might connect into the AOS which has limited access. My documentation says the AOS was replaced before I purchased the car under 10,000kms ago. Any ideas? ​​Thanks!

There's an o-ring on each end of that AOS vent hose. The left side is plugged into the AOS. Could be the o-ring but hard to say without looking at it. Regardless, it would be good to replace the AOS and address the left end o-ring. The right end is hard to access so unless it's leaking, better leave it alone. If the AOS hose needs replacement, that's a lot of labor.

Thanks Ashai, AOS was replaced in 2015 from memory, I'll have to check my records. Any chance they could just be a crack in that corrugated hose as it seems to be damp all the way along it from near the coolant tank all the way to behind the engine? Could the O ring cause the oil to spread all the way along the hose?

Hard to say as the draft in the engine compartment can help spread the leak. I would start at the AOS end and see if it's leaking or unseat there first (with a small inspection mirror).

Purple arrow http://cdn4.pelicanparts.com/techarticles/Boxster_Tech/09-ENGINE-Air_Oil_Separator/images_small/Pic3.jpg

Thanks Ashai, just to confirm is the hose number 4 in this image: It appears that the line only looks corrugated in sections whereas mine looks totally corrugated. Upon second inspection it appears there is a line of oil from under the hose. Could it be that from contact with the coolant sensor it has cause a split? What should that hose be secured to as it currently in contact with the sensor.

Here is a pic of what I'm talking about above in terms of the sensor being im contact with the hose.

Found some images that show where the hose goes. From AOS to other side of the engine, looks difficult to replace im wondering how much access there is to replace the hose on the AOS end.

I had the same issue. I did replace the o-ring on the hose where it bolts to the right rear of the engine (viewed from behind). I guess I didn't know it was hard to do because I did it with some patience and not too much drama. It did not fix my issue though. Then during replacement of the coolant tank, I broke the darn thing. It was very brittle so I am guessing it had a hairline crack or two in it somewhere causing the oil film. If you have the engine stripped down to replace the coolant tank, including dropping it down as far as possible in the car, replacing that hose is possible. It took me 2 or 3 tries to get the routing where I thought it should be. I was also able (just barely) to snap it back on the AOS by stretching my arm all the way back and down on the left side of the engine.

Yes #4 is the hose and it should not rub against anything. Sounds like indeed the hose will need to be replaced. Most likely the alternator and the T plenum will have to come off for more space.

I did remove the T plenum but not the alternator.

Thanks rockhouse and Ashai, the dealership had already replaced the coolant tank when it was in last year. In saying that I think there might be enough space for me to tackle this. How does the hose clip into the AOS? Planning on removing the airbox and throttle body if I have to my hands aren't huge so hoping I can get away with it or at least try! ​​​​​​Could I be missing some clips that hold that hose away from the coolant sensor?

Okay so got under and had a look, I definitely think it's the hose because there was a lot of oil all over the hose but not much near the AOS end. I was able to get my hand up there but is from underneath the recommended way to detach the hose and connect the new one? I felt around but didn't feel a connector having looked at the images it appears the connector is even further in.

The hose connects at the RR of the engine with a plastic flange retained by two bolts. You can just see this by removing the air box and peering down from the top with a flashlight. This is where the o-ring is that was mentioned as a replacement item. The other end of the hose connects to the AOS with a squeeze type connector. You squeeze it to remove it and push it on until it clicks to replace it. You can pretty much see what I am talking about by referring to the parts diagram above. None of the work to replace this hose is done underneath the engine. Even if you have the transmission out and the engine dropped down, and you attack the AOS end of the hose from underneath, you will be accessing the hose by reaching up and over the AOS to get to the hose connector.

Thanks rockhouse, I can see the RR end that is bolted down so all good there. As for the AOS end, did you reach in via the back facing the engine to disconnect and re connect the hose? In the diagram that has an O ring as well. Was it hard to replace that or did it sit in the hose?

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Answers in red above.

Awesome thanks! I'll keep everyone posted on my progress. I wonder if anyone has used the 997 part and routed the hose ontop of the engine rather than through it (so to speak)??

Here are the images of how the 3.6 997 engine routs that hose, which goes up behind and back to 4-6 crankcase side:

Any thoughts on attempting to use the 997 hose and clips? I'm thinking hopefully it might be easier to route and it would stay cooler as its routed on top rather than through the engine? Also there might be less effort routing it as it can be done from the top. From checking all the part numbers it looks like the AOS end would be fine as the 997.1 AOS has a 996 part number. Also the 997.1 3.6L crankcase also has a 996 part number too, so from both sides of the hose they should theoretically fit.

Okay so im going to answer this one myself, unfortunately the 997 hose is cost prohibitive at $189aud for the 997 vs $68aud for the 996. ​​​​​​So that answers that question...

Any torque specs available for the end of the hose with the two bolts? I couldnt find any information on the AOS or the hoses in the factory manual

Okay! Got this done today, steps I followed were: 1. Remove air box 2. Remove throttle body 3. Remove 1st T plenum 4. Un-do 2 10mm bolts on the bank 4-6 side 5. Reach around the back of the engine (AOS side) unplug hose, its tricky but it comes off 6. Cut cable tie holding the cable in place (under the right side of the 2nd plenum) 7. Pull out old hose 8. Route new hose start with bank 4-6 side first 9. Route AOS hose side through 2nd intake runners (back between 4-5) then across through 2-3 10. Route hose down past coolant tank 11. Reach in and plug AOS side in 12. Cable tie hose to 2nd plenum (factory is 6mm x 500mm cable tie) 13. Re assemble - T plenum, throttle, airbox 14. Test drive Only thing that would have been useful to know was that there is a 6mm x 500mm cable tie holding it in place. Hopefully someone else finds this useful in the future! Only one thing forgot to connect my MAF for a few mins so turned off plugged it in, does this affect the maps? Also do I need to perform the throttle rest procedure (car is 04' drive by wire/e-gas). Thanks!!

I didn't mention the zip tie because I wasn't 100% sure that this was a factory installed thing or something someone added to my car. I also struggled to route the hose in such a way as to be able to replace that zip tie, so I must have gone underneath something that I should have gone over the top of. I did not replace it, but the hose just sort of stays there supported by the other hoses around it. I don't think unplugging the MAF sensor messes anything up that needs resetting. Good job getting to that AOS connection w/o removing the coolant tank. I don't know if I could have reached through there with any dexterity left to actually manipulate the hose connector.

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Thanks, yeah it wasn't an easy job by any means. Reaching behind and un hooking the hose was the hardest part. I tried to get the new hose back through the existing cable tie but it wouldn't go through. Ended up cutting it using some smaller ones. I​ve ordered some larger ones so ill eventually replace it. Hose is still sitting close to the coolant sensor though :/

As it would seem 6mm is not a standard zip tie size! Whyyyy?! Anyone have a part number for the zip tie or is that being too pedantic?

Just to confirm this was indeed the hose, filled the old hose with water and watched it very slowly drip out from a section.

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Nice. Glad you got it sorted.

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Thanks for everyone's help

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Ahsai, quick question for you, do you know what this cable tie/zip tie holds onto: The second zip tie on that intake runner/resonator is the one that holds the vent line in place. Hopefully this helps someone in the future!

Interesting, I don't have that zip tie on either of my MkII engines ('02 and '03). The AOS hose is a hard line in the middle section that rests on top of the engine case. It's supported by a plastic bracket that's bolted to the engine case top.

You can see that plastic bracket in the middle of the pic that supports the aos hose (at the lower part of the bracket), the starter y-cable and some other few wire harness.

My '04 C2 does not have the support block shown in your picture, or at least if there is one in there it isn't doing anything with the AOS hose. Not a very good picture but if you look closely you can see the AOS hose zip tied to the intake runner.

Thanks guys for the pics guys much appreciated. Interestingly my AOS hose was only zip tied to the intake runner there wasn't anything else holding it in place. Next time I'm in there ill see if there are any other places that the hose should clip into. I recently had my starter Y cable replaced at the OPC who knows what they did in there. The Y cable actually wasn't clipped into a place it should have been. After tackling this I could have done that cable myself. Just encourages me to DIY more when I see things like that and corners being cut by the OPC. Maybe the majority of people don't care but in my opinion that clip or tie or whatever it might be was put there for a reason. Anyway back to that second zip tie it might be a tip thing being there is additional lines for the transmission etc.

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​​​​​​Rockhouse was there only a single zip tie for your hose as well? On my 04' there was only one but if there was a second it might have been cut by the dealership for more access when they replaced my Y starter cable? I might order another tie just in case. IMO the higher and further away from the bloc​​​​​k and from heat the hose sits (even by a few inches) the better for its longevity? Although the current one lasted from 04'. Currently have realised that this has been well overthought haha.

Yes just the one zip tie. I must have made a routing error somewhere installing my new AOS hose because I could not get the hose up high enough to reach that intake runner so did not (could not) zip tie it back into the original position up snug against the intake.

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Thanks rockhouse, same as mine only one zip tie With the routing from memory it was through the 2nd and 3rd intake then through the 4th and 5th on the other side. ​​​​​

Threads like this one make me love this site. You guys are rockstars!

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​​​​​​ Glad you like it! Just another day in the life of 996 owners haha! Helps when you have guys like Ashai and rockhouse to give you assistance too.

Gents, one last thing to add to this, if you want the correct size cable tie for the 2nd intake runner its: N 02 090 63 Officially comes from a 944 but is the exact size needed and even has the same marking on it (not that anyone might care!). Anyway part is shared across Audi, VW and maybe Skoda as well so they might keep them in stock. If you don't care tie two smaller ones together and call it a day! I wanted the challenge of finding the right size so was more about the chase than anything haha.

People, take some (reference) pictures before dismantling things!

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I have pics do you need some? This job doesn't have many reference pics as everything is mostly hidden. The AOS side of the hose has to be done by feel.

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my hose (#4) is leaking from chafing on a bracket under the right side manifold. This is all great info. Thanks! I temp repaired the hose until i need to do other work on top.

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Glad we could help, I think my hose was rubbing against the coolant tank sensor which over time created a hole. Order the extra large cable tie around the 2nd resonance tube and pull it in a little that will help with the clearance between that sender/sensor and the hose.

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Having just replaced my AOS, I suspect #5 will be the biggie for most. I tried to disconnect the tube from the AOS for a short time, but figured this would be easier once the AOS was out- which it was. Still, a nice summary and I may have to do this sometime in the future - when snaking my old tube through the manifold I think I may have heard it crack, but couldn't find for sure a break. Car seems to run fine, but only time will tell. Any other symptoms besides the weeping oil noted before you replaced the vent tube?

Number 5 was definitely the hardest in that list, you have to basically work by feel however not an impossible task it does take some patience. The tube becomes brittle from the heat and can develop very small holes, however other than it leaking out oil over time there were no other symptoms. I was actually checking my engine mounts from underneath when I noticed that the hose was covered in oil. Not enough to leak on the ground but enough to coat the hose so I knew something was wrong, luckily it was just that hose.

Hi Dan great info! I've got a weep/leak near the breather connector and the hose near the AC compressor, above number 4 cylinder. I can hardly even get my hand to that side of the connector. In your step 4. Un-do 2 10mm bolts on the bank 4-6 side. Which bolts are these? Did you have to move the cables/hoses on the right side to get the pipe through? or just stuck your hand in between and did your best. I see refridge lines/coolant pipes/other wiring all blocking access to getting that connector and hose out. Looking at part numbers, for some reason my connector has a breather on it and the hose is a smooth hose mostly non-corrugated, but according to the catalogue, these are for m96.02 cars. although i believe i have M96.03 engine. (2002 3.6L engine) So i'm a little confused on which parts to get as well. The part numbers i seem to currently have are: 99610704751 - 4 breather hose 99610714755 - breather connector Also do these come with o rings as well? Thanks in advance.

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Hey Quasio! Assuming you're on PFA with the same username! Anyway, to answer question one: Yes referring to the two 10mm bolts that are holding the hose onto bank 4-6. I didn't move anything out of the way I undid the bolts and there was a bit of room to get it out. You only need to order the hose itself it comes with everything you need, o-rings etc. the breather connector comes attached to it. Best advice would be to give your VIN to the dealership when ordering the part to make sure you get the right one. It's probably the same one i've included in this thread. Its corrugated all the way. I've also included the correct cable tie to attach the hose to the resonator pipe as well. If you need any more help drop me a PM or reply here ill get back to you. I don't remember if you're in Melbourne but if you need a hand I trade in the beer economy.

yep same guy from pfa, thought i'd reply here to give more info to others. Yeah I moved recently from melb to perth, would definitely been good for a meetup, lots of track days etc i'd love to have gone too, not much in perth. Interesting that the connector comes with the hose, i'll give the dealer a call, but pretty much their prices i don't even bother calling these days at least i can get the right part number. So the hose you replaced it with - full corrugated, is the same as your original? mine is smooth on the cylinder side, (maybe that's why it's leaking) but i'll check with them.

Had an awesome morning with the PFA on sunday actually! I get most of my parts from the dealership but I do shop around, they are usually pretty competitively priced. Don't quote me but I think the hose was only around $65 and yep came with every thing I needed except the cable tie! Yes I removed one that was corrugated and replaced it with one that was also corrugated although the middle had a smooth section. I've seen images of engines with non corrugated hoses I think thats an older style hose, mines an '04.

ok wierdly, my version of the connector has a little breather, has only 1xM10 bolt. on my engine there is no place to put 2 bolts. just the 1 at the back. Gets wierder, i checked out my engine number to ensure it's a M96.03, and it says it is.. There's also a line that goes right to the top of that bolt. so it will be interesting to move that without breaking anything.

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That is weird, haven't seen just one bolt holding the hose onto the 4-6 bank. Others on here may have though.

yeh looking at a few 2002 3.6 engines for sale, looks like the same pipe. non corrugated. now.. another question is whether it's easy to thread the non-corrugated version through the plenums, or if their interchangable but just skip the extra bolt.

There's a breather on '02 model and no breather on '03+ models. ​

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Hi Ahsai, thanks for that!, are they interchangeable? i.e. can i use the non-breather model on an 02? (just to ensure it doesn't leak anymore) and also seems easier to fit than the current pipe.

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What does the breather attach to? Or is it just part of the hose?

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The breather plugs onto the bank2 head. The AOS hose plugs onto the breather.

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The vent elbow with the breather fits a smaller diameter #4 pipe so they are not interchangeable. See pic for engine number cut over.