AOS Failure ? What should I expect to find broken?
10-08-2018, 01:35 PM
#1
Track Day
Thread Starter
AOS Failure ? What should I expect to find broken?
Hey all:
So, I had what looks to be complete AOS failure at the track on Friday.
Long-story shortened: lap #2 I got into some oil that was left on-line and took my first on-track spin. (I kept it on the asphalt :-) ). I noticed almost immediately a big blue / white cloud behind me, but I've seen the "Boxster Smoke Bomb" a number of times, so I thought it'd burn-out, as usual, and be fine. Seconds later it was clear this was not that simple, so I found a place to get off-line, pull off track and shut the motor off. They put me on the flatbed and took me back to the pits. Once there, I tried to turn the motor over; it turned for a split second, then stopped. HARD.
I towed it home and last night took a second to look it over more closely.
First things first:
The exhaust was full of oil. Every pipe-joint is dripping, as is the header-flange.
The little "vent / drain" that sits on the bottom of the air filter housing (that I remove to get to the middle spark plug on the left side) was also full of oil, suggesting it was WAY up in the intake as well.
When I pulled the middle plug on the right side, that cylinder was completely full of oil; ran out into my armpit as I removed the plug.
None of the plugs look like they have any physical damage to them, from anything hitting them. And once they were all out, the motor turns freely with the starter motor. I can hear what to ME sounds like normal valvetrain noises, nothing more. It was clearly hydraulic-locked on that cylinder.
SO: it seems I MIGHT have dodged a bullet.
TWO questions, for those of y'all who know:
1) What else should I check before buttoning it back up? I mean, should I drop the pan and look for bent rods? or?
2) I'll replace the AOS, but I'll be honest: any PCV system that includes such an easy path for the oil to dump into the intake, such as we have with this AOS system, seems like a design-failure. For decades, we've been dumping PCV into catch-cans which then vent to atmosphere, or to header-pipes, and a separate drain back to the sump. Why don't we simply do that with these motors? What am I missing? Is there a better design on the market already? What are y'all racers doing?
Thanks again for all of the knowledge base here. 'preciate your time for me!
So, I had what looks to be complete AOS failure at the track on Friday.
Long-story shortened: lap #2 I got into some oil that was left on-line and took my first on-track spin. (I kept it on the asphalt :-) ). I noticed almost immediately a big blue / white cloud behind me, but I've seen the "Boxster Smoke Bomb" a number of times, so I thought it'd burn-out, as usual, and be fine. Seconds later it was clear this was not that simple, so I found a place to get off-line, pull off track and shut the motor off. They put me on the flatbed and took me back to the pits. Once there, I tried to turn the motor over; it turned for a split second, then stopped. HARD.
I towed it home and last night took a second to look it over more closely.
First things first:
The exhaust was full of oil. Every pipe-joint is dripping, as is the header-flange.
The little "vent / drain" that sits on the bottom of the air filter housing (that I remove to get to the middle spark plug on the left side) was also full of oil, suggesting it was WAY up in the intake as well.
When I pulled the middle plug on the right side, that cylinder was completely full of oil; ran out into my armpit as I removed the plug.
None of the plugs look like they have any physical damage to them, from anything hitting them. And once they were all out, the motor turns freely with the starter motor. I can hear what to ME sounds like normal valvetrain noises, nothing more. It was clearly hydraulic-locked on that cylinder.
SO: it seems I MIGHT have dodged a bullet.
TWO questions, for those of y'all who know:
1) What else should I check before buttoning it back up? I mean, should I drop the pan and look for bent rods? or?
2) I'll replace the AOS, but I'll be honest: any PCV system that includes such an easy path for the oil to dump into the intake, such as we have with this AOS system, seems like a design-failure. For decades, we've been dumping PCV into catch-cans which then vent to atmosphere, or to header-pipes, and a separate drain back to the sump. Why don't we simply do that with these motors? What am I missing? Is there a better design on the market already? What are y'all racers doing?
Thanks again for all of the knowledge base here. 'preciate your time for me!
10-08-2018, 01:52 PM
#2
Rennlist Member
Sounds like you dodged a bullet. You can not see the rods from removing the pan. You will have to hope it didn't bend and just fire it up and listen,( and clear the smoke bomb) I have seen it before just as you described, and the rod didn't bend. Yes you can run a catch can vented to atmosphere,I've been running mine like that for a year with no problem other than a slight increase in oil consumption due to the low tension rings, but I kind like the extra oiling of the cylinders to prevent bore scoring. You can also use a catch can in-line for added protection, or use the Motorsport AOS that will also require some modification.
10-08-2018, 04:28 PM
#3
Track Day
Thread Starter
Thanks, Porschetech3. That's sorta news I was hoping for, haha.
Do I assume that is the AOS is bad? Or is it possible it gets overwhelmed after a spin like that, then drains and goes back to normal function? (there were no previous signs of failure)
I think I'll look at the idea of a catch-can in-line, so that I retain the vacuum to the system, for ring-seal, and big-brother / emissions control.
I'll also probably run a borescope around and see what else I can look at while I've got it open.
Do I assume that is the AOS is bad? Or is it possible it gets overwhelmed after a spin like that, then drains and goes back to normal function? (there were no previous signs of failure)
I think I'll look at the idea of a catch-can in-line, so that I retain the vacuum to the system, for ring-seal, and big-brother / emissions control.
I'll also probably run a borescope around and see what else I can look at while I've got it open.
10-08-2018, 07:15 PM
#4
Race Director
My first AOS experience involved a hydraulically locked engine but this happened at the dealer when I guess the tech decided to run the engine some even though the thing was smoking like crazy. I didn't think to attach a "do not start" tag to the car. (The 2nd AOS failure which had the car back at the same dealer I practically covered the car with "do not start" Post-Its.)
The tech ran a compression test which found no problems. I argued this was not part of what I had agreed to and the charge was removed.
What I would recommend you do is remove all plugs and turn the engine over by hand. If it turns over ok then after a couple of revolutions by hand use the starter to crank the engine and remove as much oil from the cylinders as possible. Pull the fuel pump fuse so you don't flood the engine.
If the engine makes scary noises being spun by the starter shut it off ASAP, but I don't believe this will be the case.
Replace the AOS. Be sure all hoses associated with the AOS are also replaced and properly connected. Be sure the oil level is ok.
Put in the plugs.
Start and run the engine and burn out the oil. This can take quite a while. The engine needs to get up to temperature and remain there. Around town driving is the best as this results in the engine including the intake gets plenty hot. The intake walls are likely very wet with oil and this oil won't immediately be removed by a brief running of the engine because the intake walls remain relatively cool. But around town with an elevated engine compartment temperature the intake can get pretty warm.
The check engine light may come up and you'll have to read the error codes and write the info down then clear the codes. The odds are the error codes are just the aftereffects of the engine/sensors/converters being exposed to a lot of oil. (Concurrent with the running the engine after the AOS failure one O2 sensor took this opportunity to go bad. So I had to deal with that in that I wanted to see with an OBD2 data viewer the actual failure which proved to be hard to do.. If I had to do it over again I'd just replace all 4.)
At some point I ran a bottle of Techron through the engine to help remove any deposits arising from the AOS failure (and any that might have existed before this).
After some engine run time if all seems well you can consider replacing the plugs. I did the first time, but the 2nd and 3rd times, meh. I just let the remain in service until they were do to be replaced on miles.
If the engine essentially runs drama free you dodged a bullet. Had the lock up occurred at some higher RPM the engine would be toast, mostly likely.
The tech ran a compression test which found no problems. I argued this was not part of what I had agreed to and the charge was removed.
What I would recommend you do is remove all plugs and turn the engine over by hand. If it turns over ok then after a couple of revolutions by hand use the starter to crank the engine and remove as much oil from the cylinders as possible. Pull the fuel pump fuse so you don't flood the engine.
If the engine makes scary noises being spun by the starter shut it off ASAP, but I don't believe this will be the case.
Replace the AOS. Be sure all hoses associated with the AOS are also replaced and properly connected. Be sure the oil level is ok.
Put in the plugs.
Start and run the engine and burn out the oil. This can take quite a while. The engine needs to get up to temperature and remain there. Around town driving is the best as this results in the engine including the intake gets plenty hot. The intake walls are likely very wet with oil and this oil won't immediately be removed by a brief running of the engine because the intake walls remain relatively cool. But around town with an elevated engine compartment temperature the intake can get pretty warm.
The check engine light may come up and you'll have to read the error codes and write the info down then clear the codes. The odds are the error codes are just the aftereffects of the engine/sensors/converters being exposed to a lot of oil. (Concurrent with the running the engine after the AOS failure one O2 sensor took this opportunity to go bad. So I had to deal with that in that I wanted to see with an OBD2 data viewer the actual failure which proved to be hard to do.. If I had to do it over again I'd just replace all 4.)
At some point I ran a bottle of Techron through the engine to help remove any deposits arising from the AOS failure (and any that might have existed before this).
After some engine run time if all seems well you can consider replacing the plugs. I did the first time, but the 2nd and 3rd times, meh. I just let the remain in service until they were do to be replaced on miles.
If the engine essentially runs drama free you dodged a bullet. Had the lock up occurred at some higher RPM the engine would be toast, mostly likely.
10-08-2018, 09:55 PM
#5
Track Day
Thread Starter
DONE.
too late, haha.
Done, and it didn't. I can hear the valves moving, but I don't hear anything I'd call "scary"
So, is my AOS for sure bad? (I know I said it was from the start, but hear me out). Is is possible that the AOS is fine, but was simply overwhelmed by the slinging of oil caused by my spin? Or will this take-out the AOS?
Here's a video from another car. He comes up on me as I'm recovering from the spin, and then you can see the rest .... haha. Anticipating the question: Yes, I pulled off track and shut the motor off. It did not lock up on me there.
too late, haha.
Here's a video from another car. He comes up on me as I'm recovering from the spin, and then you can see the rest .... haha. Anticipating the question: Yes, I pulled off track and shut the motor off. It did not lock up on me there.
10-08-2018, 11:40 PM
#6
Rennlist Member
Well if you have a manometer, it is a quick test to see if the AOS is bad,A good one should put 5-7 inches of WATER negative pressure on the crankcase. A quick start and test would verify.
Or disconnect the AOS pipe from the throttle body housing, and plug housing , Takes about 20mm plug , a 3/4-7/8 rubber expandable live well plug works well. Then run engine until smoke clears then reconnect AOS, if smoke reappears or if oil cap is hard to remove while running AOS has failed.
Or disconnect the AOS pipe from the throttle body housing, and plug housing , Takes about 20mm plug , a 3/4-7/8 rubber expandable live well plug works well. Then run engine until smoke clears then reconnect AOS, if smoke reappears or if oil cap is hard to remove while running AOS has failed.
10-09-2018, 09:44 AM
#7
Track Day
Thread Starter
Well if you have a manometer, it is a quick test to see if the AOS is bad,A good one should put 5-7 inches of WATER negative pressure on the crankcase. A quick start and test would verify.
Or disconnect the AOS pipe from the throttle body housing, and plug housing , Takes about 20mm plug , a 3/4-7/8 rubber expandable live well plug works well. Then run engine until smoke clears then reconnect AOS, if smoke reappears or if oil cap is hard to remove while running AOS has failed.
Or disconnect the AOS pipe from the throttle body housing, and plug housing , Takes about 20mm plug , a 3/4-7/8 rubber expandable live well plug works well. Then run engine until smoke clears then reconnect AOS, if smoke reappears or if oil cap is hard to remove while running AOS has failed.
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10-09-2018, 10:53 AM
#8
Race Director
There is an initial outpouring of smoke which I guess was during the spin or shortly thereafter. But not long after that, after the spin recovery, there was a much denser cloud of smoke.
Given the amount of smoke and the volume of oil the engine apparently ingested I just assumed the AOS was bad. A new one is not expensive and if you replace it yourself then you save on labor cost. Based on my experience it is a wear item -- in a strictly street driven car no less -- and with the rigors of tracking can have an even shorter life span but if you don't want to replace it unless it is bad then as Porschetech3 offered the nanometer test can be used along with some other tests to determine the AOS's current condition. Good. Or bad.
Given the amount of smoke and the volume of oil the engine apparently ingested I just assumed the AOS was bad. A new one is not expensive and if you replace it yourself then you save on labor cost. Based on my experience it is a wear item -- in a strictly street driven car no less -- and with the rigors of tracking can have an even shorter life span but if you don't want to replace it unless it is bad then as Porschetech3 offered the nanometer test can be used along with some other tests to determine the AOS's current condition. Good. Or bad.
10-09-2018, 04:13 PM
#9
Track Day
Thread Starter
There is an initial outpouring of smoke which I guess was during the spin or shortly thereafter. But not long after that, after the spin recovery, there was a much denser cloud of smoke.
Given the amount of smoke and the volume of oil the engine apparently ingested I just assumed the AOS was bad. A new one is not expensive and if you replace it yourself then you save on labor cost. Based on my experience it is a wear item -- in a strictly street driven car no less -- and with the rigors of tracking can have an even shorter life span but if you don't want to replace it unless it is bad then as Porschetech3 offered the nanometer test can be used along with some other tests to determine the AOS's current condition. Good. Or bad.
Given the amount of smoke and the volume of oil the engine apparently ingested I just assumed the AOS was bad. A new one is not expensive and if you replace it yourself then you save on labor cost. Based on my experience it is a wear item -- in a strictly street driven car no less -- and with the rigors of tracking can have an even shorter life span but if you don't want to replace it unless it is bad then as Porschetech3 offered the nanometer test can be used along with some other tests to determine the AOS's current condition. Good. Or bad.
10-09-2018, 07:12 PM
#10
Rennlist Member
Cheap manometer sufficient, like this one?
https://www.amazon.com/Hti-Xintai-Ma...70955011&psc=1
https://www.amazon.com/Hti-Xintai-Ma...70955011&psc=1
