Oil at rubber inlet tube

[RVG8tor]

Pulled the cowl to change the oil and as I inspected things I noticed all of my inlet tubes have a glisten or oil at the seam where the inlet tube is clamped with the rubber hose that joins the sump. This junction has a name I am sure but I don't know what it is. There is no oil leak but if you push on the rubber hose I can get some oil to flow out of the seam between the inlet tube and the rubber hose.

It is the same on all 4 cylinders, I am curious if this is normal or not.

Cheers

[Wayne Gillispie]

I tightened all of my "oil drain-back tube" clamps after 25 hrs along with mineral oil change. Cleaned off residual oil and they are still dry at 124.5.

[RVG8tor]

Just to clarify, this oil is at the rubber hose that connect the large cylinder intake tube to the sump. It is not the oil return line. I am concerned that there should be no oil here. In the picture below you can see where some oil oozed out when I touched the edge of the rubber hose. This is not a drip but there is oil in there.

Is this bad or normal, I have the same thing on all of my intake tubes.



Cheers

[Ron RV8]

Looks more like a little fuel seepage. Have you tried snugging up the hose clamps?

[Scott Hersha]

Are you fuel injected? Could it be trapped fuel leakage after engine shut down?

[RVG8tor]

Originally Posted by Scott Hersha

Are you fuel injected? Could it be trapped fuel leakage after engine shut down?

I have the Air Flow Performance FI. One thing I have noted is what looks like a bluish residue inside the intake side of the air box, it is something like a mix of fuel and oil. Up to now I have not worried about since I have not had any issues. It is just a bit so I have not thought anything of it. Oil burn is around 10-12 hour per quart.

I have one corner of my sump that always stays wet with oil, and the left front of the engine gets a drop or two of oil. I still don't know where they are coming from. When I saw the glisten on the intake tubes I thought that might be it but any oil there would get sucked into the engine. Front seal was suggested as a culprit but that is fine.

Still wonder if I should be worried. Planning a trip this week!

Advice welcome.

[LettersFromFlyoverCountry]

What you describe is my experience as well, although I haven't seen anything on the intake. I'm realizing that the oil I see on the engine (really just a drop here or there) doesn't seem to be coming from where I find it but probably is coming from the breather tube and ending up every which way.

I also get oil seepage on the back of the sump at the screen. That's the nut that I torque to the proper specification (I can't recall -- something like finger tight + 130 degrees or something) with a new crush washer every time. I suspect a drop or two is coming from there too.

When the plane sits for awhile -- as it does at this time of the year -- some of the oil from the very bottom of the cowl runs down the nosegear fairing and onto the wheel pant.

Again, I suspect the breather tube in all of this. It's pretty impossible, because of the engine mount on a nosegear (on a 7A, anyway), to get the tube positioned directly over the exhaust.

One of these years I'm going to put a separator in and see if that changes anything.

[Vlad]

Inspect intake pipe closer. Might be leaking intake gaskets all four of them. Easy and cheap fix.

[rocketbob]

This is a small example where product improvement is clearly non-existant on a Lycoming.

For one thing, on intake gaskets there is a very small lip on the tubes that is the actual sealing surface. Its very easy for this sealing surface to break its seal. The fix is a welded flange on the intake tube, exactly like the exhaust, instead of the goofy collar.

The other fix would be valve stem seals like some Continentals have where an excessive amount of oil would never get past the valve guide.

Anyways, done with my rant but make sure you use something to lubricate the gasket before you put it on, ie titeseal or fuel lube, so it doesn't stick and eventually break down. Its a lot easier to replace down the road if you don't have to scrape the old gasket off.

[DanH]

Like Bob says, the oil is probably from the intake valve guide. If it is not getting past the gasket at the top of the big tube, it is probably being washed down the inside of the big tube when you prime for start....thus the fuel/oil gunk in the airbox too.