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wasz
Sepang


Joined: 28 Dec 2012
Posts: 2998


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 MY99 Vesuvious Charcoal 996 | Clutch, Fly RMS IMS AOS Job |
Steering Rack Hard Lines | Air Con Compressor / System
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



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

Just googled it Cool
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



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
Dijon


Joined: 21 Mar 2015
Posts: 7589
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
Hockenheim


Joined: 08 Nov 2018
Posts: 673



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
Dijon


Joined: 21 Mar 2015
Posts: 7589
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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My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



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: 205
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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02 996 C4S
93 Skyline R33 GTS-t
91 CRX vtec turbo
01 986 Boxster S
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



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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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 205
Location: Hertfordshire


PostPosted: Mon Jan 21, 2019 11:09 am    Post subject: Reply with quote

I think exactly the same as you and do pretty much everything myself including a pair of head gaskets on my 986 recently, a new engine in the 996 a few years back however my biggest issue is time. With the cost of doing head gaskets for example, I had no choice but to do it myself and save a fortune in labour however with the price I paid to have all of the hard pipes on the C4S done, I didnt even consider doing it myself as its a really rubbish, time consuming job and then to have a proper full fluid change (inc ABS), its not a home job as you need special equipment.

If I ever get the 986 back on the road, I know that needs the pipes done as well - it will be going to straight to my indy - not a chance I'm tackling it.
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93 Skyline R33 GTS-t
91 CRX vtec turbo
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



PostPosted: Mon Jan 21, 2019 12:34 pm    Post subject: Reply with quote

I would hazard a guess that at least 7 out of 10 996’s are still on the brake fluid they left Germany with. It’ll need flushed no matter what happens.

Good on ya for doin the gaskets. Ya have to do whatever it takes to own the dream. Thumb
 
  
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Bluebird911
Nürburgring


Joined: 29 May 2010
Posts: 461



PostPosted: Mon Jan 21, 2019 12:45 pm    Post subject: Reply with quote

I would hazard a guess that at least 7 out of 10 996’s are still on the brake fluid they left Germany with.

Surprised
 
  
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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 205
Location: Hertfordshire


PostPosted: Mon Jan 21, 2019 12:52 pm    Post subject: Reply with quote

I'd like to think that more than 3 in 10 have a proper service done - at least when the car was a little younger. My 996 is on its 5th lot of brake fluid from a full change. Whilst I do pretty much all of my own work and keep all receipts from parts, when it comes to service time I take it to my specialist for a couple of reasons. Firstly its a stamp in the book and another good receipt to add, secondly he has the kit to do a proper FULL fluid change when required and thirdly I think its important to have a different set of eyes and ears going over the car - even if just for peace of mind.
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93 Skyline R33 GTS-t
91 CRX vtec turbo
01 986 Boxster S
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



PostPosted: Mon Jan 21, 2019 1:13 pm    Post subject: Reply with quote

I’d be very surprised if the fluids changed every 2 years or whatever the time frame may be. Worked in a different manufacturers dealership when I was younger and I don’t think I had ever seen it done.

I hear ya on the stamp in the book. Mine has full history. apart from 1 stamp it’s all opc and specialist. Mice to have but I’d say it’s basic oil change stuff. At least reading more into it, it is. You have to look beyond a stamp when buying
 
  
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Bluebird911
Nürburgring


Joined: 29 May 2010
Posts: 461



PostPosted: Mon Jan 21, 2019 5:01 pm    Post subject: Reply with quote

The reason I am surprised by your comment is that, as you are probably aware, brake fluid is hygroscopic and aside from the poor pedal feel associated with moisture in the fluid, 20 years of moisture infused fluid would render abs pumps and modules inoperative due to heavy corrosion of the internals.
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



PostPosted: Mon Jan 21, 2019 5:12 pm    Post subject: Reply with quote

You maybe right but it’s a time consuming thing that I’d bet just isn’t done.

Just on abs, does anyone ever delete it?
Either for track cars or due to pump problems
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7589
Location: Brighton


PostPosted: Mon Jan 21, 2019 9:00 pm    Post subject: Reply with quote

There is a lot of conjecture over brake fluid change .

As mentioned , over time brake fluid absorbs moisture .. water in essence .

This will boil at 100 degrees so the more water the more chance of this happening.

Boiling water will produce air .. in brakes it gives a soft or in extereme cases no brake pedal ... pump it and you will have a pedal though .

There are cheap tools you can buy to measure the amount of moisture in a brake system .

Every 2 years .. its a bit over kill but thats what Porsche recomend .

Now then .. these cars are not new .. not every bleed nipple will come undone.

So the theroy is you wont have a total fluid change ..

heres an example ..

Raceing blue fluid .. i changed it back to standard .. started n/s/r ..

I watched the blue fluid come out of the n/s/r .. it took over half a ltr untill it went clear .. i then did the other corners.

A standard fluid change is to take 1/4 ltr per corner out .

Basically unless you take over half a ltr out of the n/s/r then you are not clearing the line .. sucking out the resevoir would have made it less though.

A small amount of fluid left in the system wil have no impact .

Dot 4 boiling point is about 145 degrees .

Think about it .. if you replace 50 % then you have halved the amount of water in the system .. normal change and i would estimate 90 % plus .

The odd siezed nipple or indeed a total caliper would still change the vast majority of the fluid .

this is fine .

Bear in mind .. an oil change doesnt get all the oil out .. it will still leave 1 - 1.5 ltrs of oil in an engine .

Brake fluid change is aimed at getting as much moisture contaminated fluid out as possible .. in 2 years .. hmm .. not going to be much moisture in the system .
_________________
.
My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 673



PostPosted: Mon Jan 21, 2019 10:55 pm    Post subject: Reply with quote

Very well put demort. Not really a problem of changing fluid when your changing all the pipes.
Never heard of racing blue fluid. I just tend to use 5.1
 
  
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maldren
Suzuka


Joined: 07 Oct 2016
Posts: 1198



PostPosted: Tue Jan 22, 2019 9:55 am    Post subject: Reply with quote

and change to stainless nipples while you're at it.
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Mike
2003 996.2 C2 Coupe Arctic Silver
 
  
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GMG
Nürburgring


Joined: 07 Jan 2018
Posts: 464
Location: Devon


PostPosted: Tue Jan 22, 2019 10:30 am    Post subject: Reply with quote

...interesting and Iain after my recent engine rebuild and replacement over gearbox brake lines replacement the brakes were bled (takijg litres of fluid) however an inner rear drivers side nipple sheared thus this couldn't be bled...should I worry that air might be trapped in this short brake line leading to a less than perfect brake feel?

In other words do I need to rush to remove caliper and have a new bleed nipple fitted?
 
  
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