C6 S6 Throttle Body Leak and Oil Cap Suction

A6 All/ S6 All
#1

Hello all,

I have done digging on the subject and I’ve come to some of my own conclusions but some of the threads I’ve read are from as far back as 2008 so I’d just like some up to date clarification and advice.

I have a 2009 S6. The issues are the oil cap suction and throttle body leakage. I also have a rough start on cold morning but goes away within the first couple of minutes. This has never thrown a CEL yet however. I assume that may even just be carbon buildup.

I have quite a leak on the driver’s side throttle body. The passenger side may be leaking but I cannot tell.
https://youtu.be/8zwfuzLlLhU

The oil cap also has some decent suction.
https://youtu.be/vbJo7Rr6UyU

For the throttle body I’ve read of people just using silicone sealer and sealing it up with no issues.
The oil suction is more my worry. From what I’ve read a common thought is immediately PCV, I’m just wondering if there are other things that could be the culprit.

Any input would be much appreciated.

Thanks in advance.

1 Like
#2

at least for the throttle body, that’s something you can easily seal with RTV.

as for the oil cap suction…i got nothin ??? ???

#3

Carbon cleaning, if never done before, is pretty much a must with our cars. It sucks because it’s time consuming, a general pain in the butt, and can be costly for some, but worth it. While you’re in there you might as well address the fuel injectors if they’ve never been done before. JHM has a good deal on flow matched sets for around $650 for all ten after you get your car charge back.

As far as your throttle bodies, I had the exact same noise as your video. What I found to be the issue with mine is that someone before me had over tightened the bolts and stripped the threads in the upper intake, as well as slightly warp the mating surface on the intake. I used a helicoil to repair the threads and RTV to address the slight warping of the mating surfaces. No issues since. Some people take the approach of just using a longer bolt with a nut on the backside to avoid using a helicoil - it’s really just a matter of preference and skill set.

The suction on the oil fill cap could be from a vacuum leak somewhere. As you mentioned the PCV systems in our cars are pretty weak. I’d start with the oil separator behind the driver’s side valve cover and go from there. A smoke test might be money well spent if you have a shop near by that will do it for a reasonable price. The vacuum systems on our cars is pretty well buried which makes it difficult to really track things done in an efficient manner.

#4

I used the Permatex Black Sealant on the throttle bodies and on where the plentum attaches to the intake… had too many small leaks there that were driving me nuts.

As for the oil cap, the vacuum is coming from the oil/air separator. if you haven’t replaced the unit, probably a good time to.

#5

Raz Very helpful posts with the videos.

Let me echo what Nebuchadnezzar said. Make sure you really dig into things like the carbon clean and injectors that are flowed and tested. JHM is the only company that hi pressure tests and cleans the injectors. Both of these are a top priority to look into.

As to the throttle body. As the others have said. The fix is usually very straight forward. remove the throttle body and place a bead of silicone around the surface gasket area. That should do the trick there.

As for the oil cap. If you have any vac leaks that will cause the motor to have a few more rpm to keep the motor happy with the extra unmetered air. But over all you want to see suction of the oil cap like that or very close to it. Keep in mind that same suction that is pulling the oil cap back is the same suction that is pulling down on your valve covers keeping them sealed and not leaking and the same goes for the oil pan and other areas.

Obviously its a good idea to check your PCV system and oil separator to make sure its in good working order but other than that I wouldn’t worry that looks to be healthy activity.

#6

Thank you everyone with your suggestions.
The carbon cleaning was always planned as the information is not known to me if the first owner ever had it done. This beast just ticked over 77k miles. I have a local shop who only does European cars and really knows these. Right now I’m just looking for the time to take it in.
(I work in logistics for FedEx so you canb probably imagine how busy we are around the holidays)

I will give the silicone sealer a chance and see how that works. If it doesn’t, I’ll look into the stripped threads thought and see if that may be a deeper issue of mine. The oil suction is minimal. Just wanted to know if that much was necessary but from what justincredible said I think mine is probably in normal limits. Fuel injectors are also planned but that depends ok how much opening my wallet is going to make me cry.

Question on the oil separator. Is that even something able to check myself or are we talking find a good shop because it’s one of the 'drop the engine’s situations?

#7

The oil separator is something that you can remove with a little work but its deffinitly not a drop the motor kind of thing. Its connected to the intake manifold. on the back. Depending on how mechanically inclined you are you can open the oil separator or test it yourself. by applying pressure and seeing if the diaphragm holds

Yes overall your crank case pressure looks right on for how its supposed to be.