Hi everyone, in reading up for the AOS replacement on a .2, I saw a lot of complaints about the “bitch bolt” (the last bolt in the back left corner of the intake manifold.) Getting to it is a pita because the AOS diaphragm practically covers it, making it very hard to get a socket on it. I found that a very small 10mm open wrench fits in it, if your fingers are small enough to feel the head. However, as blind as it is, it’s actually easier to loosen the 2 Allen bolts on the AOS first, to push it out of the way enough to fit a very shallow 10mm socket on it with a 4 inch 1/4in extension and the smallest 1/4 ratchet that I had. I found that a shallow craftsman socket and craftsman rachet actually worked better than my snap on tools because they are smaller. Going back in was a bigger pain in the ***. I have pretty small hands and even I couldn’t fit my fingers with the bolt in between the AOS and runner, to place the bolt in its hole. Kept dropping it. The solution I came up with was this…worked on the first try, hope it helps someone else…
Secure the AOS top hoses, seat it in its case hole, start the bolts until secure, but lose enough to get a little wiggle out of it. Start a few manifold bots to ensure that it is centered. Then the back manifold bolt:
1. look through the space under the manifold behind the alternator. You will actually be able to see the hole for that bolt through there. But you can’t reach it because it’s not big enough to fit a hand through…that’s where this tool comes in aces.
2. Use a magnetic grabber tool to hold the bolt in the center and the rest is fishing!
3. With your right hand fish the bolt under the manifold. With your left hand reach around between your manifold runner and the AOS and using your finger tip, tilt the bolt into the hole. It will drop right in. Release the grabber tool and you are in business!!
4 the. Using the same small shallow socket and extension carefully massage the slightly loose AOS back enough to fit it on the head of the bolt, attach the small ratchet, and Bob’s your uncle!!
hope this makes someone’s miserable job slightly less frustrating. Was a game changer for me when I realized it.

 

👍👍👍
Thanks

 

Suggest you consider installing the UAOS vs stock AOS when doing the replacement. Lots of discussion on this forum about the upgrade and it's highly recommended.

 

I considered it and came to the conclusion the the UOS is overkill. This AOS lasted 20 years and 55k miles. I think I can live with even a 1/4 of that lifespan. I fully expect to have to have the engine out again in the next 5 years for any of the many reasons. I’ll just treat it like a major service item. Now that I’ve suffered once, I’m sure I can bang it out in half the time.

 

Some do and some don't ....Lots of people has had bad Genuine Porsche AOS's bad right out of the box, and some would fail every year, it got so bad that experienced shops would recommend replacing the AOS every three years as a maintenance item....But the UAOS having a diaphragm that is twice as thick and a Lifetime Warranty is only one of the many advantages...

IMHO there is no such thing as overkill when it comes to longevity....but free labor is hard to beat....I have a comprehensive paper coming out soon that will detail ALL the advantages of the UAOS System..

 

Failed AOS that was less than a year old killed my engine.... Required full rebuild. YMMV

 

Not going to argue that it CAN'T happen. I was a BMW master tech for many years and saw a lot of m54 engines that had sucked oil through the AOS and hydro locked. If you had my experience, you would think they are all ticking bombs...the reality is that it was extraordinarily rare for that to happen with absolutely no warning. I just feel like as enthusiasts we sometimes allow ourselves to take these rare worst case scenario horror stories and extrapolate. If you follow that thread, we all need to stop driving right now and send our engines to Flat6 to have a full bulletproof track 3.8 built because nothing else will be reliable. This is going to be a weekend toy to rip around and enjoy, not a track car or hardcore canyon carver. I'm comfortable with the failure rate of the OEM part and confident in being able to identify early signs of a failure before it fails catastrophically. Given your experience though, I absolutely understand why you would disagree that it's not worth the risk.

 

Nothing worse than having a brand new one fail 6 months later...I hate this job!

 

I thought the same thing, even being a Porsche Gold Master and having had replaced low mileage engines due to AOS failure/hydrolock, and numerous AOS's due to excessive oil consumption and smoking and obvious signs the AOS was failing...

I thought " How In the world can these owners not see the early warning signs of AOS failure? ..They must be just driving around in "911 Heaven" oblivious to the mechanical functions of the engine" ...I thought sure I can recognise the symptoms of early failure, so I was OK with the failure rate also.....Then this happened to me a few years ago...

I was at Talladega GRP Race Track with a few friends having some Track Day fun and all was well all morning with absolutely no signs of any issue, then we took and hour for lunch while the Track went cold, then when I restarted the engine after the hour break, a HUGE plume of smoke covered the car...I knew instantly what had happened, and that I just dodged a bullet without any warning that a bullet was coming my way....

This eye opening experience was what lead me to want to develop a better AOS System that not only had a "warning system" but was more efficient and more durable...

The UAOS is not just a "better replacement part",it is a "complete redesigned system", that is 4x more efficient , over 2x more durable, easier to access the diaphragm, with a failsafe warning system built in..and can even handle a higher oil fill level to improve oil starvation situations..

Overkill? I wish all things M96 were designed as overkill from the Factory...but then again most of us would not have gotten a great car for a bargain price if it had been..

 

Oh absolutely, but I can tell you this,, I have five friends in the local club, all with 02-03 996's,,, None of them have had a AOS (Other than the original....) last more than about 2 years.. My theory (With no science whatsoever... ) is the Ethanol vapor in the blow by Eats the diaphragm in the AOS up. Especially if the car isn't driven much, it drys out and gets brittle. All of the AOS fails were after the car was parked for a month or more.. What sucked is my car was fine when parked, when I cranked it it started and made the sound of 100 dollar bills in a blender and started blowing white smoke instantly.. Cracked all 3 cylinders on the left bank.. Massive oil in intake and cylinders.

I've had the same issue on a Prior BWM, at least on my engine I was lucky the AOS was the high mounted cold weather kit version (06 E46 330X1) and it typically just smoked like a crop duster when the AOS failed. (Mine popped twice in about 6 years and 150K miles I can't gripe too much.. )

NOTE I'm just wild estimating the fail rates,, all are +/- a point or two..
I don't know how much you've interacted with Jake at flat 6 , but he has more engine fail data than just about anybody on these engines, he was very direct and gave me the numbers when I was talking to him about my rebuild. He has never been a fear monger with me, he just has the numbers on engines they touch and how many of each fail they have dealt with..

In the end, statistically I feel like the stock 996 has what I call a broad line failure curve, if you go simple, say that 6% of all 996 motors will fail a IMS in < 100K, and 6% will fail a AOS with catastrophic results, and 996.2 engines maybe 2% of them will drop a valve seat, 4% will crack a head, almost 0% will blow a head gasket, 4% will fail a waterpump that will result in engine overheat thats fatal, We have 6+6+2+4+4 for a 22% overall failure rate in the non metzger 996's. (Not including the oiling issues and pump/valve-train control issues)
Which isn't bad if you divide their age in to the percentage, its about 1% per year but the line on the graph isn't straight its a standard bell curve increasing as the cars age.. A telling note is that Porsche will not tell how many short and long blocks they have used on the 996 and 997 cars, if it was < a couple percent of total production you'd think they would be bragging about it.. But of course the lawsuit sealed the information flow off.. And of course there has been no tracking of how many cars have been repaired by Indy shops globally...

Cheers..