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I have had my 996 since 2013, and I do some DE events with the car. During most track weekends I will find oil leaking off the front of the motor, and it appears the oil is coming from the AOS. I occasionally get some puffs of smoke out the tailpipes as well. I try to run with the oil on the low end of the dipstick, and if the oil level is ever higher, it seems that the symptoms are more pronounced. I do not get any of this during normal, street driving. Anyone else ever have this issue? Is this the sort of thing that the motorsports AOS is supposed to cure? Back around 2015 the original AOS was replaced with a new, standard AOS. That did not cure the problem.
Keeping the oil level low on the dip stick for a car used at track events is never a good idea, especially on a 996!
After you replaced the AOS in 2015, the issue never got better? Did you find the previous AOS to be defective? Did you find oil anywhere where it shouldn't be?
I have had my 996 since 2013, and I do some DE events with the car. During most track weekends I will find oil leaking off the front of the motor, and it appears the oil is coming from the AOS. I occasionally get some puffs of smoke out the tailpipes as well. I try to run with the oil on the low end of the dipstick, and if the oil level is ever higher, it seems that the symptoms are more pronounced. I do not get any of this during normal, street driving. Anyone else ever have this issue? Is this the sort of thing that the motorsports AOS is supposed to cure? Back around 2015 the original AOS was replaced with a new, standard AOS. That did not cure the problem.
At higher g's the AOS can become overwhelmed, and suck oil into the intake. This is more pronounced with the .2 cars ('02 and up) due to slight design changes. As you go faster with stickier tires, it can get worse (it is NOT good for your motor). So yes, this is why the Motorsport AOS is used in many track builds.
Edit: as for the oil leak, that is not associated with Motorsport AOS or lack there of. The crankcase vent system may be compromised somewhere. The exact location of the oil leak should be determined.
Your symptoms are common. First. as said above, just make sure where your oil leak is originating.
Unfortunately the AOS is one of the Achilles heals on a 996. Track driving puts a real strain on the AOS, and can show up on the track but not during normal street driving. However, it also means that the AOS diaphragm is getting weak and will eventually fail. Sudden failure of the AOS can result in a hydro-locked engine...…..very bad, especially if it happens on the track. I've just put in my 2nd AOS in 9,000 miles because of lots of track events.
FYI - You can install the stock Porsche AOS for significantly less than the cost of doing the Porsche Motorsports version. The Porsche Motorsports version requires quite a bit of plumbing alterations if installed in a stock 996. Stock AOS is less than $150, the Motorsports version is around $800-$900 (plus all the extra installation labor). Lastly, the Motorsports AOS is not fail-proof either. There are instances of it failing too.
Just budget $1000 and replace your AOS if that's the problem.
P.S. For track events, you want to keep your oil level at the half-way point on the dipstick, i.e. not full. Check it manually on the stick, not with the display on start-up.
Thanks for the feedback! I installed a deep sump a few years ago, and I keep an eye on the oil pressure. No problems with that so far. I started my last track event with the oil level near the top of the dipstick (yes, I love having a real dipstick!), and blew some clouds of smoke. I wish I had a decent picture of the oil leak, but I don't. Looking at the motor from the front of the car on the driver's side, up where the AOS resides, there is oil on the AOS and dripping down the front of the motor below the AOS. Other than the mess, it doesn't seem to be causing any particular problem. I just keep an eye on the oil level.
When I did replace the original AOS with a standard replacement, the symptoms returned the next time I was at the track.
I have had my 996 since 2013, and I do some DE events with the car. During most track weekends I will find oil leaking off the front of the motor, and it appears the oil is coming from the AOS. I occasionally get some puffs of smoke out the tailpipes as well. I try to run with the oil on the low end of the dipstick, and if the oil level is ever higher, it seems that the symptoms are more pronounced. I do not get any of this during normal, street driving. Anyone else ever have this issue? Is this the sort of thing that the motorsports AOS is supposed to cure? Back around 2015 the original AOS was replaced with a new, standard AOS. That did not cure the problem.
This is one reason I'm glad I had my AOS changed out during my clutch service. I looked at the higher end Porsche motorsports AOS, but it was crazy expensive at around $800 compared to the $150 standard version. Since I didn't plan to track my car, I didn't give it a second thought, but I'm heard they are much better for tracking applications.
I bit the bullet and installed the Motorsport AOS. On sharp left sweepers I would get smoke, sometimes a lot. Never happened under any other condition. MS AOS fixed the issue.
I think I had this problem after my track day yesterday. After got home looked the car over and saw some oil had dripped down front of motor on passenger side. Following it up, I see some oil on this corrugated tube that runs under the intake manifold runners on the passenger side. The AOS itself is dry though.
I started my tack day with oil slightly above half way on dip stick. Car has LN 2QT deep sump.
The car ran strong, had solid oil pressure and ran cool for temps in mid 80s. Did not see any visible smoke and no one mentioned seeing any while I was on track.
Since the AOS itself is dry, does that rule it out and I should be looking elsewhere ? Can has not leaked any oil during street driving.
I think I had this problem after my track day yesterday. After got home looked the car over and saw some oil had dripped down front of motor on passenger side. Following it up, I see some oil on this corrugated tube that runs under the intake manifold runners on the passenger side. The AOS itself is dry though.
I started my tack day with oil slightly above half way on dip stick. Car has LN 2QT deep sump.
The car ran strong, had solid oil pressure and ran cool for temps in mid 80s. Did not see any visible smoke and no one mentioned seeing any while I was on track.
Since the AOS itself is dry, does that rule it out and I should be looking elsewhere ? Can has not leaked any oil during street driving.
The AOS line run on the back of the engine just next to the accessories. The black corrugated tub you see here I believe is the wire loom?
that black pipe is the line running from the AOS to bank 2. I’ll update this post with a picture.
IMO if there is ANY sign of the AOS sucking up oil you need to test it ASAP. This is sign that you potentially dodged a bullet from hydrolock.
Look on the marketplace, there is a user selling oil caps used for hooking up a manometer to test your AOS or make one yourself.
I would also strongly advise you take a look at the UAOS solution from another user on this forum, especially if you track the car.
Well, your wrong. The AOS pipe is only corrugated close to the AOS on the left side of the engine. This is the right side and you can see the oil cooler, the AOS line does not run that close to it. Here is what the AOS line looks like: https://www.rosepassion.com/fr/schem...10714753-57258
Fyi, my original aos line was corragated on both ends of the tube.
I would guess that if the aos was dry, then the tube may be cracked. U may have sucked oil up through the aos and it drained out the tube. U should test the aos a precaution and check the tube.
Well, your wrong. The AOS pipe is only corrugated close to the AOS on the left side of the engine. This is the right side and you can see the oil cooler, the AOS line does not run that close to it. Here is what the AOS line looks like: https://www.rosepassion.com/fr/schem...10714753-57258
Okay.... Well you're wrong....
See pictures below....
And one more point... you can see VERY CLEARLY the other wire loom you are speaking about below in his picture (see Red circle). Also see the additional picture below that one that CLEARLY shows the difference in what the wire loom piping vs the AOS piping looks like.
07-15-2019, 11:22 AM
Oil leak from AOS (?) during track weekends
