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Old 12-23-2014, 05:12 PM   #1
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AOS part number Cayman/Boxster HP version

98710792600 = $1524.35 << full pop retail from Porsche

It's MORE expensive than the 996 version, but will save you money/time during the install. The 996 version (it was developed for the 3.6/3.8 996 non Meztger) DOES not fit the Boxster/Cayman engines very well. It runs right into the M97 electric smog pump bracket!! The More expensive version I listed above? It clears everything. It is slightly smaller than the 996 versions (where it needs to be)

Contrary to popular belief (and contrary to what *most call it) It has NOTHING to do with "motorsports".

This will NOT fit any Boxster engine prior to 03

I'm up to 6 people this year asking me "how to" fit the 996 version to their cars AFTER buying the wrong one from Pelican Parts. It would take a home user 8-10hrs to modify everything to install the 996 version when the Boxster/Cayman specific version takes 1hr.
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Old 12-25-2014, 09:30 AM   #2
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Very helpful post -thank you Mr. Roberts.
Here is a thread that has a detailed diy install:
987 MOTORSPORT AOS INSTALLATION - Articles
The price of the part is horrid ! It is a pity that whatever internals make this 98710792600 part so much better can't be found as an upgrade to fit all Boxsters/Caymans.
The problem of using the 996 part and it conflicting with the AIS pump bracket - is this another incentive to remove the AIS and do the ROW reflash ? Thereby eliminating two sources of problems?
I have seen a photo sectioned ,failed AOS .The diaphragm splits apart. replace with a small circle of Teflon/Kevlar/Viton ?
Factory AOS / VOS Replacement - Articles
Air Oil Separator (AOS) Diaphragm - Rennlist Discussion Forums
Surely there is a better alternative to a $1500 part or repeated(even more expensive) failures ?
Apparently the much cheaper (but uograded) 996 unit can be modified to fit:
Modified Motorsport AOS install
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Old 12-29-2014, 10:55 AM   #3
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I have a much cheaper solution I sell to my customers. I found the exact same diaphragm... for $38. We make our own canister
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Old 12-29-2014, 11:52 AM   #4
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Elsewhere it was mentioned that overfilling the engine with oil(particularly at oil change time) contributes to premature failure of the diaphragm.
Interesting to note that some others explain that the deficiency that causes AOS diaphragm failure is insufficient capacity of the 'tank'. Since space is so limited where the stock AOS is located, this implies a solution requires some relocation of the oil/oil mist condensation/oil recovery tank.
Some have achieved this by cutting off the connections of a failed AOS and then connecting to a much larger tank located in the trunk. I guess it would be important to position it so it could be checked easily and frequently? A lister suggested using a tank from Jegs.
But whatever you selected it would need a diaphragm that mimicked the Porsche one.
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Old 12-29-2014, 12:46 PM   #5
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The main issue I see with *some people and their home brewed solutions?? (Jegs catch can) they forget that it needs to DRAIN back into the block!! They keep draining them into a pan outside the car and forget THE OIL NEEDS to go back into the engine LOL (I've seen this on track cars multiple times) then don't understand why the engine is low on oil

The aircraft industry has used AOS style devices for years.

The Porsche solution? add capacity so it has MORE time to drain back. The real issue is: the smaller ones do NOT have time to drain back into the engine when ran hard. Porsche knew they had an issue in the Boxster's in 03. They changed the block to match the 02 3.6L drain back. The steel tube inserted into the block was nearly twice as big as the opening in the 2.5/2.7/3.2/3.4 M96 engines.
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Old 12-29-2014, 01:03 PM   #6
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Very useful caution. Thank you. The consequences of a misguided experiment to out-smart Porsche with a diy AOS could be a damaged engine!
The old school catch cans seldom have any diaphragm or valve in them. But newer designs may have a one-way valve or even two valves. I wouldn't like to be the guinea-pig to determine the correct valve(s) or tank capacity! The options and cost of failure are daunting.
15 Mustang GT Plug N Play SC Oil Catch Can Separator | UPR
11-14 Ford F150 Ecoboost 3.5 Dual Valve Catch Can CSS
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Old 12-29-2014, 01:06 PM   #7
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The diaphragm I use? Is identical to the Porsche AOS diaphragm. It comes from another German vehicle
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Old 12-29-2014, 01:08 PM   #8
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Neither of the solutions you linked too have a DRAIN BACK!! They are for "oil mist/vapor" not full on overflow from our heads
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Old 12-29-2014, 01:16 PM   #9
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Let's be clear, I offered NO solutions and much caution.I am just curious about this as a 10 cent part problem that can cause $$$$ damage.
BMW have a similar AOS problem and their enthusiast Forums have tinkered with several diy catch cans.Some have a drain back. Just depends how many exhaust ports on the can and where they are located.The BMW application is much easier than ours because of engine design and space.Now their motor cycle engines are another story.........
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Old 12-29-2014, 03:24 PM   #10
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Subaru flat 4 turbo engines have similar issues but they have aftermarket solutions-just 1 example:
Air/Oil Separator - WRX/STi/LGT/FXT - GrimmSpeed
The Subie enthusiasts recommend one catch can per bank and water cooling them !
Best STi Air-Oil Separator | How-To Weed Out the Bad from the Good
Interesting to note that none of these manufacturers offer a specific after-market part for Porsche M96.
Aftermarket Air Oil Separator
Back to Boxsters - here is a helpful diy link:
Replace the Air/Oil Separator
https://sites.google.com/site/mikefocke2/airoilseparatorreplacement
There are a few 'hits' where someone crowed about inventing a diy AOS alternative for the M96 but then there is total silence.No "I've done 20,000 miles with it and it works great" follow-up !Beware.
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Old 12-29-2014, 05:43 PM   #11
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Porsche P/N 98710792600

Hopefully the stars will be properly aligned tomorrow.. :-)

So I can get the correct AOS (P/N 98710792600) as suggested by Brad Roberts
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Old 12-30-2014, 11:11 AM   #12
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One more question about AOS

Brad,

Can you help me getting an AOS P/N 98710792600 with a discount..?

Thanks in advance!
Gilles
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