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wasz
Magny-Cours


Joined: 28 Dec 2012
Posts: 2700


1999 Porsche 996 Carrera 2

PostPosted: Mon Jan 14, 2019 10:50 am    Post subject: Reply with quote

Quote:
One of the most common failures in the Boxster is the Air/Oil Separator, also referred to as the AOS.
The AOS is basically a small diaphragm distillery which distills the minute amounts of oil mist in the crankcase, liquifies it and sends it back to the crankcase. The “clean” air is now sent into the air intake (after the throttle body) to be burned off by the engine.
When the AOS starts to fail it cannot separate all of the oil out of the mist and some liquid oil is sent to the air intake.
A few drops of oil is enough to generate the GREAT SMOKE BOMB for which our cars are famous for.
A big smoke bomb once in a while is completely normal, due to the architecture of the flat-6 engine, which may let a drop of oil flow into one of the combustion chambers sporadically.
But if you car smokes on a regular basis, this is the telltale sign of a bad AOS.
Don’t let it go on for too long because it will only get worse and eventually, enough liquid oil can pass into the combustion chamber to cause hydro-lock which may cause terminal damage to the engine.


From http://www.pedrosgarage.com/Site_3/Replace_the_Air_Oil_Separator.html

That link is for a boxster, on the 996 it is a whole world of pain unless the gearbox is out, then it is a bit easier to do. Simple with the engine out. Worth swapping if you have the gearbox /engine out as its so difficult to change in situ.
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My special order Vesuvious Charcoal 996 | Clutch, Fly RMS IMS AOS Job |
Steering Rack Hard Lines | Air Con Compressor / System
 
  
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NedHan79
Monza


Joined: 08 Nov 2018
Posts: 189



PostPosted: Mon Jan 14, 2019 11:30 am    Post subject: Reply with quote

Just googled it Cool
 
  
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NedHan79
Monza


Joined: 08 Nov 2018
Posts: 189



PostPosted: Mon Jan 14, 2019 6:43 pm    Post subject: Reply with quote

crash7 wrote:
There is a flexible kit available, but I cant remember where I saw it!

Hel will make custom brake hoses for you if you decide to go the flexible route.


Sorry crash. Just saw your comment. It’s definitely something to consider. It’ll only be a short term job as sooner or later the gearbox will have to come out for a clutch and rms. And to check, clean and paint the chassis.
 
  
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5735
Location: Brighton


PostPosted: Mon Jan 14, 2019 7:37 pm    Post subject: Reply with quote

NedHan79 wrote:
Thanks wasz. I’ll get a look when I get time this evening.
Just one question, I see AOS mentioned a lot. What is this?


Air Oil Seperator .. when it starts to fail or indeed fails you get a " fair bit " of smoke out of the exhaust pipes .

The rubber pipe attaching it , if the bellows type it can also split and induce air leaks causing the car to run lean .. same as leaveing the oil filler cap off basically .

On a manual car then in theroy it can be done in situe .. after my last atttempt i swore i would never try to do one again without dropping the engine ..

To the point that if the customer didnt want to pay for that then he can take it else where i think was my final comment to the service advisor .
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NedHan79
Monza


Joined: 08 Nov 2018
Posts: 189



PostPosted: Mon Jan 14, 2019 8:14 pm    Post subject: Reply with quote

Cheers demort. Seeing as you know so much, I’ll not take any offence if you wana just do it for me. Free of charge obviously Very Happy

Seriously though, it seems that this site is worth its weight in gold for advice and tips.
A big thanks to everyone Thumb
 
  
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5735
Location: Brighton


PostPosted: Mon Jan 14, 2019 8:20 pm    Post subject: Reply with quote

Young man .. there are very few jobs on Porsches that i end up throwing my toys out of the pram ..

So far an alternator on a turbo Panamera and these dam AOS are the only times ive had a rant ..

To be fair the alternator job and i was about to walk out the door and i HAD the Porsche instructions on how to do the job .. Total crap are the Porsche instructions .. not just the normal useless ones which i often see ... but utter crap instead !
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NedHan79
Monza


Joined: 08 Nov 2018
Posts: 189



PostPosted: Wed Jan 16, 2019 9:18 pm    Post subject: Reply with quote

wasz wrote:
OK you should check my thread linked in my sig: http://911uk.com/viewtopic.php?t=124928

The only time I served as a mechanic was under my dad's watch as a kid (a time served engineer) and I managed just fine on my back on axle stands.

I dropped the gearbox, flywheel, locked the cams and checked / re-sealed the IMS bearing, swapped the AOS and replaced the brake pipe.

My brake pipe had been spliced under the cover previously as DeMort described. In the hidden clips above the gearbox the old steel was pretty grotty so inspect it well if you are considering that.

I can imagine it would be possible to get a brake line in without dropping the box, but very fiddly, and likely not exactly matching the original route - probably easier with knifer as you can bend it more easily in place. I wanted to match the original to make sure it wasn't going to rub.

Not a hard job just really frustrating and fiddly I image......easy to drop the engine and gearbox a few inches I think for better access.

**** Also check the brake line that runs along the front in front of the steering rack. Mine was well grotty.

I have done all the old steel brake lines and flexi lines on my car.

I would not want a long flexi line, it would lead to that brake being slightly less efficient and move around a lot / risk rubbing through.


Finally got a read through your thread. Looks like I’m gona have to get busy when I get the all clear with the back.

Great work thumbsup
 
  
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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 196
Location: Hertfordshire


PostPosted: Fri Jan 18, 2019 1:39 pm    Post subject: Reply with quote

I needed to do all of mine and really didnt fancy it so got my indy to do it when he serviced the car.

We used the original Porsche lines and did all of them including the full length of the car as well as flexies and the caliper hard pipes.

The 4S is also more painful on the front to gain access to the 'across' pipe so he also had to drop one of the radiators. I had the PAS hard pipe replaced at the same time as a matter of course whilst they were under there. On the rear, they lowered the box down but didnt remove it - whilst painful its possible. I'm told the female apprentice with very small hands came in incredibly useful whilst getting the new line in position.

The price was also so good that I wouldnt even consider doing this job myself. The pipes are expensive from Porsche if you buy them all but no way round that as I wanted to stick with the originals rather than making them up myself. The labour was fantastic so if you're near Hertfordshire, give Archer Motorsport a call. I use them for all work now that I dont fancy myself and I'm lucky enough to have a ramp in my workshop - I just hate working with brake lines.
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93 Skyline R33 GTS-t
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NedHan79
Monza


Joined: 08 Nov 2018
Posts: 189



PostPosted: Fri Jan 18, 2019 5:05 pm    Post subject: Reply with quote

It’s good to get another bit of experience from someone having to get it done. I wouldn’t be paying anyone to do it as I hate the thought of paying for something I can do myself. I used to be lucky enough to earn more by working and pay someone else to do it but those days are gone.
Besides, half the classic car ownership is the work involved.
I wonder if my 8 year old son could get his hands in Floor
 
  
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