Smoke at Track - Possible AOS Failure??

I have a 2002 996.2 6MT 117k miles yada yada that I recently bought from a member here to use as a track/daily/beater. I believe it came with a failed AOS which of course was not disclosed to me (among other things). First hint should have been the smoke coming from the exhaust as the transporter was unloading it from the trailer. I have done 3 track days with it. One at sebring and two at homestead. Each time I have a similar issue. I start the day with the oil level close to full, both on the dash and on the dipstick. When I take a hard right turn the car feels like it hesitates and when I look back there is a huge cloud of smoke behind me. It seems like it burns oil until it gets to the bottom of the dipstick/dash and then it doesn't burn any more. If I put more oil in it, it gets burned again until it gets back to showing almost empty. While the level shows low the car runs great. Seller claimed the engine has a baffle installed but I have not removed the sump to confirm. And now when I look up the post to get all the info he specified he deleted all the info and just says SOLD. I hate when people do that !!!! Moving on. Last time at Homestead I noticed the level was a little low after the first session so I put some more until the level showed sufficient. This time I forgot to replace the oil cap - I know stupid mistake. Needless to say when I came back in there was a mess. Oil all over the back and dripping down onto the exhaust. So I cleaned it all up, Put more oil again and tightly secured the cap. But it kept on burning the oil until it got to the bottom of the dipstick and dash. Once at that level it would not burn any more. My though was that if it was overfilled then that would explain the strange behavior. But being at the bottom of the range does not seem like overfilled to me. After the last session, when I started the car up to go home, it blew some smoke from the exhaust for about 20-30 seconds which had not happened before. Get the car back to my shop to take a look. I took out the airbox - nice and clean. Removed the throttle body expecting to find a mess but it too was nice and clean. Inside the first plenum (didn't remove the second) was also nice and clean. It did not look at all as if oil was getting in there. I mean barely a coating. Looking at all the videos and searching this forum I saw that one way to check the aos was at the filler cap. I don't have a manometer but seems like it's time to buy one (unless someone wants to lend me one). There is definitely vacuum there and the idle does drop a little and become less stable. Otherwise the car runs great. Should I just bite the bullet and replace the aos? I'm not the least intimidated by the job but would rather not do it if I don't have to. You Tube

If you are going to track it, those long sweepers make the oil slosh to one side of the engine. Mainly it is right hand long sweepers that moves the oil over and up the AOS inlet from the oil pan. This is a very common problem tracking our cars. Many stories on here about just that topic. What to do? Replace the AOS and get the UAOS solution. It's in a thread here somewhere, just do a search. Here it is https://rennlist.com/forums/996-foru...ps-tricks.html

Yes, zbomb had a ton of oil in his intake after an AOS failure. Oil getting into the cylinders = no good, you'll end up with bent rods.

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You need to do a crankcase manometer reading. This would prove conclusively that the AOS is bad. You Tube

I had a similar issue of smoking after hard runs at the track. A few days later it will be fine and no longer smoke. Learning the hard way, I found that if you run your oil level between the lines instead of full it should alleviate the smoking issue.

Have the AOS checked just to be sure. However my car did the same thing my first few track events until i too was informed of keeping the oil level well below the MAX line. Any time the oil level is slap full and you track it she is gonna blow smoke BAD!

Yep. I installed the 2 quart deep sump and run the oil level half way between the marks on the dipstick. Also use Driven XP9 oil (low foaming). No issues at Road Atlanta, including some really hard laps by my instructor.

Sebring has seen a lot of dead M96 engines.

I'll chime in as some are familiar with my story. 2QT Dep Sump Spin on filter Driven XP9 Oil Stock AOS - no issue on the street - first track day with the car, oil at about 3/4 full - a spectator mentioned they saw a puff of smoke from the tail pipe a couple times while they thought shifting up a gear. After the day noticed an oil leak later confirmed to be coming from the AOS crossover pipe. I attributed the issue to running over filled and moved on. The factory AOS was installed less than a year prior and my thinking was it was unlikely to be bad showing no other symptoms - smoke on startup, oil consumption etc. 2nd track day have the oil just barely showing on the dip stick. Come in from the 2nd session of the day and my friend tells me when I started the car prior to the session it billowed out a large smoke cloud, I did not even see it. Decided to call it a day to investigate further, Confirmed when I got the car home and on the stands the leak from the crossover pipe was back and decided to start pulling intake pieces apart. Found the plenum to have a thick coating of oil and puddles in the bank 2 intake manifold. As I was running the oil level at the lowest I felt comfortable I now ruled that out as the culprit and decided it was time to replace the factory AOS with Porschetech's UAOS and replace the cracked AOS crossover tube while I was in there. Since replacing I have not had any oil consumption / smoking issues. Thats my story.

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I found that when I run it at the bottom of the line on the dash and hardly nothing on the dipstick it no longer smokes. It's an uneasy feeling running it at that level but maybe I just need to get over it That's not good for me because Sebring is where I do 80-90% of my track days. All my track cars have been mezger engines so this is a whole new thing for me Mine usually happens going from 3rd to 4th. Is there a common place where the crossover pipe is known to crack so I know where to look? How does a cracked crossover pipe cause smoking? Too much air getting sucked into the AOS system? Or did it leak out and smoke from falling on exhaust? Also, as I mentioned, when I took the plenum off the inside looked very clean. Wouldn't a failed aos send lots of oil into the intake?

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If that's the case, installing an Accusump just went to the top of the list of what needs to be installed on your car. I wouldn't trust anything else if Sebring was my home track. The oiling system on the M96 is not a good design and most upgrades fall short for M96s used at the track.

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My crossover pipe was zip tied to the rear plenum crossover and I believe it cracked right where the zip tie was securing it to the bank 2 side. When I pulled it out it was super brittle and cracked at the touch so no way to do a good post mortem on it. The cracked cross over did not cause the smoking, the excessive volume of oil going through it did expose the leak though. The smoking was from the oil that was seen in the plenum and intake manifold being combusted. The first time I had my issues (when I thought oil level was just over filled) I also only had a light covering of oil in the plenum - the next track day I had puddles in the plenum...

I find that almost everyone that tracks their M96 996 has this story as it is evident in the replies. I've experienced myself too. 2 qt sump and new aos/motorsports aos/UAOS seems to be the most cost effective way to control the problem, but not eliminate it due to the design of the motor.