Possible Oil leak on a new engine? M20E 1975

[ighazali]

Hey everyone not sure if this is concerning. My current oil consumption is about .13qt per hour so essentially 1 quart every 7.6 hrs. Today when looking through the cowl flap door where the breather tube and blowout valve is I saw some oil on an intake pipe. Any ideas if the O-ring may need to be replaced. Oil pressure and consumption seem to be okay. Oil analysis also came back stating a healthy engine. 

[N201MKTurbo]

Most likely running down from above. There is no oil behind the O-rings.

[ighazali]

1 hour ago, N201MKTurbo said:

Most likely running down from above. There is no oil behind the O-rings.

Thanks! So nothing to be concerned? Also is the oil burn normal?

[LANCECASPER]

7 hours ago, ighazali said:

Hey everyone not sure if this is concerning. My current oil consumption is about .13qt per hour so essentially 1 quart every 7.6 hrs. Today when looking through the cowl flap door where the breather tube and blowout valve is I saw some oil on an intake pipe. Any ideas if the O-ring may need to be replaced. Oil pressure and consumption seem to be okay. Oil analysis also came back stating a healthy engine. 

When you say "new engine" is this a factory overhaul or re-man, an engine specialty shop overhaul or a field overhaul?

[Aaviationist]

Also the fact that that it can’t be coming from the intake doesn’t mean “nothing to be concerned about”

 

you need to find where it’s coming g from to make that determination. 

[skykrawler]

New engine?  I guess those are Teflon hoses (replace on condition), otherwise they look kind of oldish.

Sources of oil from 'up above' include the rocker box gaskets, rocker box drain B nut connections,  intake manifold gaskets, push-rod tube seals, and even exhaust flanges.  Engines that 'pool oil' in the cylinder at shutdown can leak it at the intake and exhaust stack connections.  One mode of this is oil coming down the valve stems. The #2 intake runner is most susceptible to chewing it's gasket due to it's length.    If it doesn't leak out the flange it will likely end up in the induction chamber where the four intake runner connect.  The next time you flood the engine some oil will wash out the sniffle valve.

But....what you're seeing is a relatively small amount of oil compared to a quart.

IMHO.

[N201MKTurbo]

6 hours ago, ighazali said:

Thanks! So nothing to be concerned? Also is the oil burn normal?

It doesn’t sound like you are going to run out of oil, but it should be fixed, if for no other reason, so your airplane doesn’t look too ghetto.

[Flyler]

Lycoming says allowable oil consumption is up to about .65qt per hour for your motor.  So you are far from that.

[Ragsf15e]

So to “Carusum” (summarize), 1 qt in 7 hours is just fine but you should look into it because something isn’t right and it won’t get better by itself.  It’s probably not urgent.

[cliffy]

I hate oil leaks!  I want my engine to rust away from the outside not be preserved in a bath of oil!  :-)

My guess is the rocker cover drain tubes hose couplings above.

Just found my prop governor cap leaking on last trip so off it comes next week in annual.

Antique airplanes take constant maintenance just like old Rolls Royces  !!  :-)

Don't fall behind on the job.

[ighazali]

6 hours ago, LANCECASPER said:

When you say "new engine" is this a factory overhaul or re-man, an engine specialty shop overhaul or a field overhaul?

It is factory overhaul was done back in 2023 only has about 100 hours on it

[Jsno]

Your oil return line clamps probably need tightened.

[ighazali]

Had a A&P check it out he said that I was missing a screw on the cylinder head cap which is the grey caps towards the top of the engine, however that cylinder was not the issue. He said the front cylinder cover cap had a bit of oil so it might be the gasket. However, he tighten the cylinder head cover cap and then told me to keep an eye on it. If it still leaks it may need new gaskets where the cap goes. Will keep you guys updated. 

[Ragsf15e]

9 minutes ago, ighazali said:

Had a A&P check it out he said that I was missing a screw on the cylinder head cap which is the grey caps towards the top of the engine, however that cylinder was not the issue. He said the front cylinder cover cap had a bit of oil so it might be the gasket. However, he tighten the cylinder head cover cap and then told me to keep an eye on it. If it still leaks it may need new gaskets where the cap goes. Will keep you guys updated. 

Those square caps cover the rockers and are a common leak source.  When you look closely at them, see if you can tell what kind of gasket is in there.  There’s an older cork (or paper?) one and a newer silicone type (Ive seen orange).  Both can leak if too loose or too tight, so that sucks.  I have had better luck with the silicone ones.

[Nico1]

On 11/23/2025 at 3:55 PM, Jsno said:

Your oil return line clamps probably need tightened.

Check this. Follow oil return lines Under the cylinders, pita to reach.