Oil on #2 Cylinder Intake Flange

[DSmith]

I just completed my condition inspection and performing a runup before cowling it up. I didn't have any leaks at the usual places but I had oil on the #2 cylinder intake flange and drips down the intake pipe. I was able to tighten the flange bolts just a little. There was no oil on the cylinder or anywhere else around the area. I know the propeller blast can throw oil all around but that intake flange is behind my air intake box. The valve cover gasket looks dry as well as the oil drain from the valve box.

Why would there be any oil at the intake flange to leak out regardless of the gasket condition?

Any ideas of where I should look?

 

[DanH]

... I had oil on the #2 cylinder intake flange and drips down the intake pipe.
Any ideas of where I should look?

Bad intake flange gasket. May as well replace all of them. Cheap paper. SDS sells an o-ring retrofit kit.

 

[lr172]

very little oil residue will come out of the intakes. If the oil staining is more than slight, I would look closer for a leak in the cover gasket or the oring on the intake pushrod tube. If there is enough oil to be dripping all the way down the pipe, it is unlikely to be coming from the intake, especially if it happened after one engine run. Sitting gas can become oil as it evaporates, but this takes a long time to produce visible oil stains.

Larry

 

[DSmith]

Dan Horton and IR172; It was a fairly long run up so when I put it back in the hangar I saw this oil on #2 intake tube - was not just a drip but maybe a half teaspoon of oil that had dripped down on the intake tube. It was on the intake flange and a drip hanging on the inside flange bolt. I couldn't see anything coming from the valve cover gasket but it almost has to be that?

 

[lr172]

Dan Horton and IR172; It was a fairly long run up so when I put it back in the hangar I saw this oil on #2 intake tube - was not just a drip but maybe a half teaspoon of oil that had dripped down on the intake tube. It was on the intake flange and a drip hanging on the inside flange bolt. I couldn't see anything coming from the valve cover gasket but it almost has to be that?

Definitely not coming from the intake, unless you have a serious clearance issue with the intake stem/guide AND a fully destroyed gasket. Don't forget to look at the intake pushrod tube oring. If that is the problem, you should see an oil trail on the back side of the head below the tube. This would likely drip down the backside of the head and directly onto the intake flange.

Larry