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So some of you will be aware some of the first D3 S8's off the production line have had problems with inlet manifolds, there are plenty of stories of the flaps getting broken in the inlet manifold.
I too drive an early edition of the S8 so idle hands led me to have a look to see how things were today, thankfully mine are ok at present.
The following images and videos give you and idea of what to do to inspect them and how to go about it.
You will need to remove both air inlet ducts from the throttle bodies, like in the following two photo's
Intake pipe removed
Intake pipe removed
Crankcase hose separated from fine oil seperator
Bracket that is obscuring one of the fixing screws,<br/><br/>Remove bracket to gain access
A hidden screw that is the same size torx head as the other screws, its fixing the fine oil separator to the bracket on the throttle body
Plenum removed so you can get an idea of where the screws are that need removing
Plenum removed ready for insertion of camera, Iphone 6 is great for this
Looking up the inside of the inlet manifold at the flaps
Linkage rod to transfer movement to other bank of flaps
Linkage rod to transfer movement to other bank of flaps
A not so healthy inlet manifold, note the broken flap in the bottom of the manifold and others hanging down.
The small video of the Manifold flaps being tested using the Output tests of Module 01
This is an easy job with very little tools if you have the slightest bit of mechanical common sense, so don't be scared to have a go.
From the oil pooling it looks like the fine oil separator has allowed oil vapor into the intake, there is probably carbon buildup at the intake valves.
A borescope like a Ridgid SeeSnake micro with 9.5mm head could be snaked past an open flap, now that you have the plenum off.
There will always be oil vapor in the intake though no?
Unless one were to dump the oil vapor into a catch can with an atmospheric vent..
however, it seems OPs intake is squeeky clean with no broken flaps, and then he provided a sample picture of a broken flap manifold if I am not mistaken?
From the oil pooling it looks like the fine oil separator has allowed oil vapor into the intake, there is probably carbon buildup at the intake valves.
A borescope like a Ridgid SeeSnake micro with 9.5mm head could be snaked past an open flap, now that you have the plenum off.
I have a borescope but didn't go for it, I was only wanting to look at the flap valves.
Yes the last picture is another car with higher mileage and a clear issue.
The very nature of the fine oil separator lets oil mist into the inlet manifold on these engines because at full throttle the crankcase gas flow is too high for it to work so it bypasses straight into the intake.
I currently have 70k on my motor but I am in the process of getting the equipment together to do walnut shell blasting so I will be having the inlet manifold off in the near future to have a look.
I've been reading about hydrogen carbon cleaning as I'm about to pick up an FSI car. Seems like it's not very widespread yet. It would be a much better solution than having to remove the manifold and blast the valves.
Hydrogen carbon cleaning could only be effective in the closed combustion chamber under ignition, but the problem is at the back of the valves and intake area.
Notice how they market this service, they are vague as to where it works.
Besides, even if it was effective where the carbon is baked on, you don't want the diamond hard carbon entering the combustion chamber where it would cause scoring, and then into the catalyst where it would clog with any particle larger that it's cells.
Walnut blasting with valves closed is the current state of the art.
I solved the carbon buildup problem in my GT4 with a VTA modification, and will be doing something similar with my S8 before I get it cleaned.
run a catch can instead of routing back to intake?
ECS tunign has a very nice looking catch can, high and small particle filter. I made a large home made version for my truck that then sucks it in pre turbo-works decently but it's still nto 100%. I can get half a pint in about 2-3 weeks daily driving.
Vent to atmosphere/catch can mod may cause issues of its own with the manifold no?
Just looking at the oil residue in my inlet and thinking that must be lubricating the flap mechanism, if it were totally dry what would the repercussions be from doing that?
Like I mentioned earlier its currently st 70k miles and if that is all that's accumulated in that time is it something to worry about, time will tell I guess when I pull the manifold and see what the inlet valves are going to be like.
Since it is a plastic mechanism, and isnt under constant motion and/or load, it would require no lubrication. Especially if it is a PTFE plastic, (dont know what it is made of).
But I agree, looks very clean for 70k miles, looks like your separator is working good! Curious to see about the valves though.
Regarding the walnut blasting, I havent found a port adapter yet for these cars, like for BMW they have ones where you hook up the shop vac to the top, and stick the wand in the side. Its all contained right there, very minimal debris get out of the intake tract of the head.
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Just looking at the oil residue in my inlet and thinking that must be lubricating the flap mechanism, if it were totally dry what would the repercussions be from doing that?
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Better. Add to that oil mist you see the water vapor you don't see. The latter is more the killer for crap build up. On any cold start you have water vapor inside the crankcase that goes through the PCV/oil separator. If you look at catch can pictures, assuming its not some tired motor on way out, a lot of what it catches over time is water.
Not just academic. I had to replace my 2000 C5 4.2 Rube Goldberg manifold three years ago. Froze at the shaft points from vacuum drive into manifold. Pot metal broke trying to get them out and it was all done. I had externally lubricated them twice previously, and never had any broken arms either. First caught it when I pulled a head, and it was junk by second head pull a few years later. Unrelated internal engine issues led to head pulls. When I looked into it, the issue is typically not water ingress from the outside, but rather that shaft area is not properly sealed from the inside. Hence water ingress. As far as I am concerned, whole thing is a long term ticking time bomb (> 10 years) on every 4.2, 3.x and what ever other NA motors have them from what I saw if designs are similar. Honestly glad it wasn't on W12, and irrelevant on any turbo or S/C motor. A stereotype overly complicated German design destined for some precision craftsmanship museum display at Ingolstadt Forum in 10 more years.
07-26-2016, 01:43 AM
S8 Inlet manifold flaps inspection
