Oh No The Jägermobile Broke Today!

[Mark_T]

Originally Posted by Jake Raby

Absolutely not. Manifold vacuum is heavily dependent upon atmospheric conditions and thats what gives the diaphragms inside the AOS their biggest workout.

Before the AOS failure was well known we'd always receive cars with this failure that were thought to have "blown engines" from areas near sea level with California and Florida always having the most, along with the entire east coast. We receive calls and keep logs from all over the USA, its not like we only see local cars, and in fact its quite opposite as we have Porsches here from 30 states now and only one of them is from our own state.

I've never had an AOS failure called in from Denver or any other area of higher elevation. When I travel across the US to instruct my Porsche engine schools I quiz the attendees on several things and one of those is "Who here has seen an AOS failure?". The trend data I have gathered has been priceless.

BTW- Suby engines also have AOS issues, especially those with high boost as the changeovers from + to - manifold pressures are hell on them.

Well, the things you learn as you go through life, eh? Hopefully 750 ft above sea level is enough to not experience this. Thanks for the explanation, Jake!

[Jager]

Thank you for the information Jake... I will keep a spare AOS available for the next time... There will be a next time.

I installed the new AOS today and got the Jägermobile back on the road... Sure was smoky for a few minutes. I will probably change the spark plugs this weekend.

I cut the AOS diaphragm casing to take a look inside and here is what I found:









The material of the diaphragm was flexible but tore very easily. There were at least three holes that were visible.

[Paul]

Looks like a $20 part, wonder why they cost so much?

Glad you are back on the road.

[DennisAN]

It reminds me of the old vent valve on MGBs and Spridgets back circa 1970.

Someone suggested that engine braking could harm the AOS, but the greatest use of engine braking is from long descents in the mountains. Jake said living in higher elevations causes few AOS problems so I think this would imply that severe engine braking shouldn't harm the AOS.

[healthservices]

Originally Posted by DennisAN

It reminds me of the old vent valve on MGBs and Spridgets back circa 1970.

Someone suggested that engine braking could harm the AOS, but the greatest use of engine braking is from long descents in the mountains. Jake said living in higher elevations causes few AOS problems so I think this would imply that severe engine braking shouldn't harm the AOS.

Less atmospheric pressure in the mountains vs. sea level, less pressure differential on the diaphragm, less stress on the diaphragm.

[Perfectlap]

Jager, How many miles are you gettting on each AOS? Assuming you drive consistently.
Have the intervals been shrinking?

[Jager]

Originally Posted by Perfectlap

Jager, How many miles are you gettting on each AOS? Assuming you drive consistently.
Have the intervals been shrinking?

The intervals have been approximately three years and between 62,000 and 71,000 miles. The last AOS had just over 62,000 miles on it but I have been driving harder (higher RPM average) than previous years.:dance:

[Perfectlap]

Interesting my aos went right in those averages as well.

[Jager]

The date I purchased my last AOS was 4/8/2011.

[oc-boxster]

Just so I know, If (when) mine fails how far is safe to drive while blowing a smoke screen from a failed AOS?

[Mark_T]

Shut it down immediately as there is a danger of hydro-locking a cylinder with oil, in which case a bent rod is the best you can hope for.

[healthservices]

Originally Posted by Mark_T

Shut it down immediately as there is a danger of hydro-locking a cylinder with oil, in which case a bent rod is the best you can hope for.

Danger of hydrolocking is low if the motor is running as the oil will go into the intake as a heavy vapor/mist not a full on liquid. Restarting after a tow maybe another matter as oil collected in intake may run off and pool into one of the cylinders, which is still unlikely. But better safe than sorry.

Sent from my SM-T310 using Tapatalk

[Jake Raby]

Engine braking produces the highest vacuum that the system can see. All you need is a manometer to attach to the oil cap to see these things.

And its all you need to check the health of an AOS.

[Frodo]

Originally Posted by Jake Raby

Engine braking produces the highest vacuum that the system can see. All you need is a manometer to attach to the oil cap to see these things.

And its all you need to check the health of an AOS.

Jake, is this something that basically any mechanic can quickly/easily do? Don't know if you've read any of my "AOS?" thread or not. I've got an appt to replace the AOS, but they're tied up for a couple of weeks before they can work on it. I'm just curious whether I can easily figure out if it's safe/advisable to drive the car in the meantime.

Any input appreciated

[Timco]

Originally Posted by Frodo

Jake, is this something that basically any mechanic can quickly/easily do? Don't know if you've read any of my "AOS?" thread or not. I've got an appt to replace the AOS, but they're tied up for a couple of weeks before they can work on it. I'm just curious whether I can easily figure out if it's safe/advisable to drive the car in the meantime.

Any input appreciated

Just get a manometer and drill / thread a tap into an extra oil cap. Some better meters record so it can be left in the trunk.

Just get one in PSI, not "WC.

[Frodo]

Sure...but who's got "an extra oil cap" layin' around? Not me

I'm a LONG way from wealthy (BELIEVE ME!), but at the moment I don't have lots of time on my hands. If having someone else quickly and reliably checking this for me is an available option, I'd jump at it.

[hancock1701]

I was thinking about this issue the other day. I replaced mine 20k miles ago at 120k and cleaned the intake interior very well. I just checked the engine a couple days ago and saw shiny wetness around the rubber boots connecting the intake plenum to the manifold. I haven't looked inside yet to see how much oil is in there, but is that a normal, or my AOS is not doing its job?

[Frodo]

Originally Posted by Frodo

Jake, is this something that basically any mechanic can quickly/easily do? Don't know if you've read any of my "AOS?" thread or not. I've got an appt to replace the AOS, but they're tied up for a couple of weeks before they can work on it. I'm just curious whether I can easily figure out if it's safe/advisable to drive the car in the meantime.

Any input appreciated

NOBODY knows the answer to this

[Jager]

Originally Posted by Frodo

NOBODY knows the answer to this

Frodo,
You have multiple questions here. I can say any skilful mechanic can change out an AOS. You have to raise the car and work above and below the vehicle to remove and replace the AOS.
You can drive your Boxster if the AOS failure is minor, that is if the hole in the AOS diaphragm is small. I would guess many of us have driven our Boxsters for quite awhile with a failing AOS before the symptoms got worse, and then continued driving until we got the replacement part. The risk is if the hole gets bigger or the diaphragm tears while you are driving and there is a huge smoke screen behind you, shut down the motor ASAP.

[Frodo]

Thanks, Jager. I was actually curious about Jake's statement about assessing the health of someone's AOS (as in using a manometer on it). I've got an appointment to have it replaced and was just wondering how far down the 'failure path' it had gone. Based on what I told him, the mechanic who's gonna work on it said it was okay to drive it. But wanting to avoid the more catastrophic forms of AOS failure, I was hoping to get some sort of more quantitative measurement of how bad (or not bad) my AOS really is. (They can't work on it for a couple weeks.)

Yeah, I have no doubt these guys will do a good job on the replacement. Heck, given a few hours (I'm slow but persistent) I'm pretty sure I could change it. I've just got too much going on right now to tackle it.

Thanks again.