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Old 07-14-2014, 06:04 PM   #1
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Did I blow my AOS autocrossing? Help me diagnose it!

I did my second SCCA autocross yesterday in the 98 Boxster (72K miles, unknown maintenance history). I've owned this car since May, and have driven 3000 miles now.

About 2500 miles ago I changed the oil. I filled it using the dipstick and it came out full scale on the electronic meter (maybe overfilled - one square past the line). I didn't know about the electronic meter then.

2500 miles later, with no problems. I often (but not every time) check the oil with the electronic meter, and it has always been the same, one square past the line.

After yesterdays autocross I drove home (20 highway miles) and put the car away. A couple hours later I decided to wash it. I started it to back out and there was a big puff of smoke

I left the car in the garage overnight and all day. I started it this evening and check the oil level with the meter. It was two squares under the line. I started it, and there was a big puff of smoke. It lasts maybe 2-3 seconds then is over.

I pulled the car out and let it idle to warm up. I shut it down, waited a little bit, and restarted with no puff. Engine was still warm.

I then drove it normally for 20 mins or so, came home, shut down. Waited maybe 15 mins, started again. No puff. Interestingly, the oil level on the electronic meter reads only 1 square low when the engine is hot. Not sure I really trust the electronic meter.

Tomorrow when it is cold I'm going to check the oil with the dipstick, then with the electronic meter, then start it. I'm expecting the big puff.

So, can you guys help diagnose this?
  • Is there a chance my AOS is OK? Somehow the lateral acceleration in the autocross forced some oil somewhere it shouldn't be?
  • Is there a chance my AOS is just partially failed?
  • Is there a test I can do to be sure?

Most important question: Should I drive the car if I get a big puff in the AM?

Second most important question: Who is going to help me change out my AOS if it is failed?

PS - I forgot to mention - this all happened right after I took off the bra in the front.....maybe she's mad ?

Here is a link to a video of my poor autocross driving. Don't make fun of me, I'm learning.
https://www.youtube.com/watch?v=tfUeUq2_06E


Last edited by DG Boxster; 07-14-2014 at 08:56 PM. Reason: added video
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Old 07-14-2014, 07:09 PM   #2
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It's not the bra.

Start the car. Take the oil cap off in the trunk. Put your palm on it. If it is a very gentle suction....your AOS is *probably* fine. Gentle sucking is normal. However, if there is a very strong pull on your palm, that's a nearly 100% sign your AOS is dieing.

As far as replacement if needed....my local Indy quoted me around $400-$500P/L. Or do a lot of reading and DIY. :-)
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Old 07-15-2014, 03:00 AM   #3
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Most important question: Should I drive the car if I get a big puff in the AM?

https://www.youtube.com/watch?v=tfUeUq2_06E

No. If the AOS fails catastrophically, it can suck in enough oil to hydro lock the engine, which will destroy it. Get it replaced.
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Old 07-15-2014, 04:08 AM   #4
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I occasionally get some smoke with my '06, it seems to happen if I run it hard before shutting down ?
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Old 07-15-2014, 05:43 AM   #5
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Update - good news and bad?

The good news is that the oil level is right where it always has been (full on the dipstick, and full on the electronic gauge).

The better news that that there was no smoke at startup.

BUT - I took Tucker2's advice and opened up the oil cap when the engine was warmed up. There is definite suction that you can hear and feel. When I remove the cap the engine idle gets uneven.

I can't tell if this is "strong" suction, but it certainly isn't faint. I have a vacuum gauge I could hook up there somehow if there was a good/bad spec for the AOS.

I don't want to tear into this if it is OK... but if it's bad I'll do it. I just need to know the difference for sure. For all I know it has been this way for 3000 miles as I never pulled the oil cap when it was running before.

Thanks for any advice!

dave

Last edited by DG Boxster; 07-15-2014 at 05:44 AM. Reason: added name
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Old 07-15-2014, 06:57 AM   #6
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When the AOS goes there will be so much suction at idle it will be hard to remove the oil cap. A little to moderate suction is normal and the idle should get higher when you remove the cap.

A high or irregular idle with the oil cap closed can also indicate a blown AOS.

Its common that racers on the bigger tracks force oil in to places that results in a puff of smoke after a day of racing, and I suppose it could happen with autocross as well.

Losing your AOS will be very obvious as your idle will be a mess and you will leave clouds of smoke so thick you will white out your neighborhood.

You will also notice high oil consumption. I lost a quart in one day my AOS died. On startup I had a puff of smoke and 10 minutes of driving later I had rough idle and then the final massive spectacular smoke bomb effect. I was freaked out and then laughing hilariously at the ridiculousness of the whole scene.
Oncoming drivers looked horrified and I was hoping no one would call a fire truck and douse my car with high pressure water.

Use the dipstick to check oil as the electronic indication is only reliable under some circumstances. (Cold engine left sitting for an hour on level ground)

Continue to drive it and monitor the oil level for a few days.
I think you'll be all right if the smoke puffs go away after a few drives.
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Old 07-15-2014, 07:53 AM   #7
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My first AOS also failed at ~80,000 miles. Which seems common from what I've read on here.
Sound to me like time was more the issue than autocrossing.

Also might want to do the waterpump or at least replace the coolant cap which has probably lost its seal if its the original. But do the water pump anyway. That failed at ~80K miles on my car as well. A bad AOS and/or waterpump are two things that can take down the engine. Well three if you count that old coolant cap.
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Old 07-15-2014, 09:29 AM   #8
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I do not really think it is your aos or anything to worry about, but there is nothing wrong with preemptive maintenance.
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Old 07-15-2014, 12:59 PM   #9
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Failed - No
In some stage of going - Possibly
About time to change it preventatively - YES

Several, including my indi, leave the oil a few bars down...overfilling may lead to premature AOS failure.
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Old 07-15-2014, 02:05 PM   #10
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Yeah....it sounds like your AOS is either normal or in the very beginning stages of failing. I agree with the others....monitor things (oil use and suction on oil-fill and smoke) and I think you'll be OK.
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Old 07-15-2014, 08:49 PM   #11
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So far so good, no more smokin'

The Boxster has been fine all day, with normal oil levels and no smoking at startup. I think the auto cross driving caused some oils to somehow get into the intake, but apparently this isn't abnormal for these cars after "spirited" driving.

Thanks to all who responded. I'm going to continue to watch carefully, and check the suction at the oil cap every once in a while as well.

I have found evidence that this car was well cared for, so it may not have the original AOS. I wonder if I can find a part number or date of manufacture on the outside of the AOS. If anyone knows where these markings are, feel free to post a picture.

Thanks again, this is a great forum.
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Old 07-16-2014, 12:28 AM   #12
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Hi,

what is the meaning of "AOS"?

Thanks!
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Old 07-16-2014, 03:57 AM   #13
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Air
Oil
Separator

Quote:
Originally Posted by Smallblock454 View Post
Hi,

what is the meaning of "AOS"?

Thanks!
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Old 07-16-2014, 04:05 AM   #14
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Thanks, Beer.

The german translation for this part is "Ölabscheider".

If this part is broken, the engine will burn much oil in general, not only sometimes. And you will allways have a lot of oil smoke from the exhaust.

There is a description on pelicanparts: Pelican Technical Article: Boxster Air / Oil Separator Replacement - 986 / 987

There are differences over the years. Attached photo shows a 1997 AOS. Part number is 99610702351. Part number stands on the side of the AOS.

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Last edited by Smallblock454; 07-16-2014 at 04:29 AM.
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Old 07-16-2014, 05:44 AM   #15
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Cool video and looks like a fun autocross. What app did you use and what platform?
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Old 07-16-2014, 11:58 AM   #16
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I have a Garmin Virb Elite camera and used their Virb Edit software. The data overlays are built in to the software and are very configurable.

Last edited by DG Boxster; 07-16-2014 at 12:10 PM.
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Old 07-16-2014, 12:12 PM   #17
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I have a Garmin Virb Elite camera and used their Virb Edit software. The data overlays are built in to the software and are very configurable.
Very cool, looks like a perfect setup for autocross.

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