Oily Grime Behind Throttle Body

[cab713]

Does anyone know what is causing the oily grime on the hose clamps just behind the throttle body on my 99 996 C2? It's on both sides nearest the boot but not any farther back. There is much more on the drivers side. My neighbor does have a spec of this on the drive side clamp of his 99 996 C2, but no where near as much as mine.

This photo was shot looking over the oil filler hose and dip stick.

Edited August 20, 2011 by cab713

[logray]

Guesses.

Leak from oil filler tube (accordian thing in lower right of your pic)

Leak from intake plenum itself.

Leak from AOS tube going into T/B above that area.

[cab713]

I've searched for AOS issues. The replacement DIY seems to show oil in the upper intakes that may be similar, but I have no white smoke at start or rough idle.

I'll start with the intake plenums as that is the only place I can see grime right now. The oil filler tube seems to be totally clean from what I can see. I'll confirm while getting after the intake plenums.

Thanks!

[logray]

I wasn't speaking about the AOS specifically going bad. That is in a totally different part of the engine (on the top of the drivers side towards front of car).

What I was talking about is...

There is a tube that goes from the AOS to the y-plenum behind the throttle body.

The connector for that tube is right on the y-plenum behind the throttle body just above where you are mentioning you see grime.

That tube (and it's connector at the y-plenum behind the throttle body) has a rubber o-ring that can go bad over time and leak or the tube itself can separate from the connector to the T/B or it might not even be properly connected.

It is very hard to detect small leaks in the oil filler tube without a smoke machine (crack could be in the bottom of a pleat). Chances are if it hasn't been replaced in 12 years it might have a leak (it is plastic). Mine literally just broke off after 12 years.

As for the intake plenum, it could be one of the large rubber boots are damaged, or a clamp not tightened down fully.

Some of these items would also probably be accompanied by a rougher than normal idle.

Edited August 21, 2011 by logray

[Loren]

In most cases I've seen - if you have a leak in the oil filler tube you will get a fault code (air leak).

[logray]

The tube I am most suspecting connects to the opening on the y-plenum circled in red. The other end of that tube goes to the air oil separator.

It could also be a leak in the tube itself, if not the connector or the o-ring.

Edited August 21, 2011 by logray