Oil Leak, but where?

I have an oil leak. It is coming from the driver's side of the engine but I can't identify the location. I know I need to clean it, I'm not sure the best way to do that in order to not damage the rubber hoses and fittings and wires. Here's a picture from the bottom of the engine and a picture from the top. From the top, I can't see any signs of an oil leak. From the bottom is looks like it could be coming from anywhere. Are there any common areas that this could be leaking from? ​​​​​​​

2nd pick is the bottom of the aos and bellow. Good chance its that rubber accordian hose (aos bellow). That motor is a mess. If u get it up on a lift u might ne able to get some engine cleaner up there and rinse if off?

Thanks for the letting me know about the AOS bellows. I'll try and change that. Yes, I definitely need to clean that engine. I don't have a lift, so need to figure out the best way to do it. I think I have PTSD from washing the car and not realizing water isn't supposed to go in the grill and then spending a day fretting over what it wasn't running right...Until I looked up on Rennlist and found that you're not suppose to spray that part of the car.

Another question, if I clean this area of the engine with simple green and wash it over with pressurized water, I assume there is some risk that the water and de-greaser will make its way into the bellows if there is a crack or hole. I don't know the how the AOS works, but is there any risk of damaging the engine if water and simple green gets into that area as I'm cleaning off the gunk that built up over time?

Yes, that risk is there. The grit carries the highest risk of causing damage, more so than the water or simple green. Personally I would scrape the majority off anything metal, then use petroleum or diesel and a tooth brush to get it properly clean. Brake cleaner would work well too but don't spray at full blast. Whilst doing so keep the crud on the bellows and turn to cleaning that at the very end just prior to removal.

Good tip, thank you!!!

WD40 is the best to clean dirt, oil & grit from the motor. I wouldn't use brake cleaner.....it dries out the rubber, plastic etc....where WD40 actually moisturizes them.

Makes sense, thank you!

Jeeper is right. The leak is coming from what's called the "bellows tube" - that accordion tube he mentions. You want to change your AOS sooner than later, otherwise you will run into a plethora of unnecessary problems down the road. If you let it go, you'll eventually hydrolock your car with oil. Can be avoided, but you have to act on it soon. If you daily your car and don't track it, a Porsche genuine aos is fine ($150). If you track it, you'll want to look at a motorsports aos, or there is a forum mate on here, porschetech3, that has developed a more durable/reliable version of the porsche motorsports aos, called the ultimate aos. You can search it online.Best of luck.

FYI - the motorsports AOS is not a direct replacement, it takes DIYwork to make it fit. The UAOS is direct fit, makes the AOS unit at the back of the engine a permanent fixture, moving the part that fails (diaphragm) to just besides the throttle body for easy replacements if/when it fails. -Tom

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+1

I swear ya'll are in on some sort of pyramid scheme here Op, UAOS by pt3 is a great product. Here's the website Ultimate AOS

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Hah! No, when you have owned a 996 for 22 years and use it on the street and track, you learn all about it and what parts are sub-optimal. To put it another way, you learn to recognize when a newly invented part is better. So you spread the word to help the guys out that are new to the 996 community and haven't had all of the experiences just yet. The point i always make is that there is nothing wrong with the M96 engine. Its a very durable engine. The problem is that there are a few lousy "bolt-on" parts that create all the problems such as: AOS (smoking, oil consumption, intermix, hydralock), IMSB and an old water pump (head/cylinder cracking, intermix). If you get a better AOS, better IMSB and keep your water pump fresh, you have mitigated a large probability of sudden catastrophic failures. For sure, bore scoring is not sudden but instead is a slow and painful failure. But it is easily addressed as well. Just run lots of high quality oil with alot of moly and change it often and you have won a good portion of the battle against bore scoring. Problem is most owners changed their oil every 15-20k miles and destroyed their bores as a result. Sure, there are bolt on parts as well that need to be used to prepare the car for the track that we haven't discussed in this thread. But you get the idea. The 996 is pretty easy to keep running strong. But you gotta know the whats and hows.

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^^ This is very true, The Porsche Motorsport requires DIY of the 19mm hoses and conectors to fit......also if going on a 996.1 it requires an $800 adapter to fit the 5 chain engine...making the total cost for 996.1 over $1600 + DIY work But I would not even recommend it at any price due to the oversize body holds 1/2 qt oil that is needed in the Sump to supply the oil pump to avoid oil starvation.. UAOS is 4x more efficient and is a no brainer...

Oh, btw, you don�t have to worry about getting �water in the grill�� there are drains in the bottom of the air box� If this were really a problem, you wouldn�t be able to drive the car in the rain. Cracked coils will give you misfires if you get them wet�

My vote for engine grime removal is LA’s Totally Awesome. It works. It’s cheap. It cleans everything pretty well, even garage floor stains, oil on shirts, etc.

Totally Awesome is great product, I buy it by the case at Dollar store.

Thank you all for the information. I cleaned up the engine with W9-40 and that worked well. I'll take the bellows off just after I grab something to eat. hkovalcik , you mentioned I need a new AOS. I prefer not to install one until I need one, but why do you think I need one? The oil leak is solved (I think). Car runs well. No smoke, no coolant leak, idle is normal, no CEL. I have an autocross event coming up next week and was planning on going, but now you have me worried... dporto - yes, I think I have cracked coils unfortunately.

Forgot to mention, I can feel a hole in the bellows on the side facing the rear of the car, so that is definitely where the leak is coming from.

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You have a place for unmetered air to be drawn into the engine. Don�t drive the car until you fix it, for your engine�s sake.

Yes, definitely won't drive the car, Got the bellows out. There is a hole about the size of a pea near the base of the bellows. Just above that hole there is a crease where it looks like the bellows got sucked into itself. Maybe the vacuum is too strong? I have a new bellows coming in on Tuesday. I'll buy a manometer too. It seems like I need to rig up some kind oil cap connection to the manometer. Once the new bellows is installed I'll test the vacuum from the oil cap to see if the AOS is functioning normally. I'll rather be driving this car than working on it, but I guess if the AOS is bad I'll go ahead and install the Ultimate AOS. I'm not the best mechanic, so not excited about it...

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Kinda but not really....its really air excaping/entering the crank case. The system is suppose to be sealed so the aos functions properly. That being said if u can get it fixed i would test the aos. A failed aos will cause high crank case pressure and cause the bellow to fail. Its probably safe to run the motor but autocross? Your call, your motor.

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Oh right, that makes sense.

So, I got the new bellows on and tested the vacuum. With engine cold, the reading was -6.53 in H2O. When warmed up a little bit (needle just before the 1 in 180) it reads -5.87. Does anyone know the actual spec for crankcase vacuum? Online I just see around 5 inches H2O. Not really sure what that means. I guess -5.87 is around 5...Which would make me feel fine, but when I drove it today at maybe 1 out of 5 stops the revs didn't settle immediately, it would jump up from 650 RPM to about a thousand or so RPM, then down to 650 RMP , then bounce up to 800RMP and then settle at 650. In one case, it just keep bouncing until I started driving. If I go to the last autocross event of the session, I need to register tonight, but it's about 170 mile drive and don't want any unnecessary damage to the engine from a bad AOS or something else, so I'm not really sure what to do. Any thoughts about the AOS?

Could the bouncing RPMs be from not installing the bellows correctly? Apparently the new house clamp for the top of the bellows is a worm screw type clamp. I clamped it down hand tight with a screw driver, but there is no spec on how tight that should be and I worried about getting it to tight on the plastic AOS or cutting the bellows, so I got it hand tight without really forcing it tighter. Maybe that is what is letting in air and causing the rpms to bounce at idle. The car never did it before at least not frequently to the point where I noticed. The bellows is the only thing that is different from the time when I drove it last and there wasn't any RMP bouncing issue then. The other weird thing was when I turned the car on, the first time I started it since changing the bellows, it wanted me to wait 56 minutes while the computer re-programmed itself. I don't know why all of a sudden it needed to do that since I didn't do anything with the battery and only jacked up the car and changed the bellows. 56 minutes seemed a bit excessive. This might have been a mistake, but I ignored the message and just started the car.

Those manometer numbers look good. I would go to the auto-x. U still might have a vac leak in the intake but i shouldnt hurt the car in the short run. The best way to check is with a smoke machine. There is a handful of vac lines, plastic fittngs and even the rear plunum flap that could be letting unmettered air in. U may also have to just clean the idle air sensor. They get clogged and sometimes stick.

Great! Hopefully I can track down the air leak. Thanks for all your help!!!

What you are experiencing is exactly - to a T - what I went thru before I eventually had to change my AOS (and yes I did eventually hydrolock the car with oil). I'll only say it once - change your AOS in the next 200-250 miles. That idle behavior is the very first sign. I used a worm clamp on the bellows tube and it eventually slipped. It is probably partially off, or keeps slipping because the diaphragm has failed inside the AOS putting excess stress on the tube itself. I am speaking from firsthand experience going thru this myself and changing the bellows tube myself, then changing the AOS myself.

@ hkovalcik , thanks for the tip. It sounds like I should really tighten down that worm screw clamp. If that doesn't stop the idle fluctuations, I'll do a smoke test, and if there is no vacuum leak that causes the RPM fluctuations I'll change out the AOS. I want to put a new oil cooler on there and switch out the starter/alternator wires so need to take a bunch of stuff off the engine anyway.

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The worm clamps will not have as clean of a hold as the snap clamps. These come pre-set from Pelican (do not have part number on me, but you can search for them). They are almost impossible to put on with the existing AOS in the car. I did not succeed when I tried, hence the worm clamp work-around, but don't believe anything is impossible so feel free to try. I am a decent wrench and will be impressed if you get it on with the AOS still bolted to the car. Again man all of this is solved with a new aos, which I think is what you should do sooner than later. Edit- Would like to make it clear that I am certain your AOS is on its way out if the bellows tube has gone once before. Whether the torn bellows tube causes a failed AOS over time, or if the AOS causes the failed bellows tube I am still unsure of. People will say it's the diaphragm that goes bad, then the bellows, but I think it's the other way around. The bellows rips first, in my opinion, and it's not from the aos being faulty. it's just a cheap tube that sees extreme temp and flexes (you can tell by the way it's connected).

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You Tube

I tightened the worm screw hose clamp as much as I could with a screw driver and the car drives perfectly now. I think hkovalcik is right that there is some risk that the worm screw hose clamp isn't the best, but it is currently the part that Porsche recommends rather than the snap clamp. Can I drench that whole worm gear in loctite or something similar to keep it from backing out? I think the AOS is fine and at the moment, I don't think there is a vacuum leak, so the car should be fine, but I just want to make sure the same thing that happened to hkovalcik doesn't happen to me.

It won't back out. If anything, the rubber hose will give were the clamp sits thereby reducing the clamping force but that will take a few years. That is the benefit of those factory-fitted clamps over worm-drive clamps: they clamp with an almost constant force irrespective of shrinkage or heat expansion of the parts clamped together.

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Who told you a worm clamp is what Porsche recommends for the bellows? I'm not saying you're wrong, just find that highly unlikely. Again I would change your aos......................

The dealership told me and showed me the on their computer because I couldn't believe it. I still didn't believe it, so looked it up on Rennlist while at the Porsche dealership. Here's the part number --> 999 512 551 01 and here is the Rennlist thread --> https://rennlist.com/forums/996-foru...ernatives.html . I have to tear apart the engine bay anyway to do the starter cable and oil cooler, so might as well do the AOS also...but the car is running strong, vacuum seems good, no smoke, no weird idle, I'll be surprised if the AOS is bad, but an upgrade to the UAOS is probably worth doing while everything is apart.