Oil leak under Cylinder No.2

[Janat83]

Hello Mooniacs!!

Yesterday I was pulling the spark plugs out of my 1968 M20C O-360-A1D , I noticed oil leak on the left side of the engine (picture 1), and when I looked at my Cylinder No.2 I saw burned oil on the exhaust manifold (picture 2, 3), I pulled out the spark plugs and It was obvious that Cylinder No.2 bottom spark plug has more oil than other spark plugs (picture 4), my mechanic said it could be from spark plug washer, he said to put new copper washer and torque it to specs and watch it, what do you guys think?

 

Thanks in Advance

Moustafa

 

[carusoam]

First you have to have oil getting into the cylinder...

Second you have to let that oil escape the cylinder...

Third, the oil is escaping to the outside of the exhaust system...

That’s a lot of escaping...

 

oil can get to the spark plugs a few ways...

Rough cylinder walls caused by rust, and subsequent removal of the rust, leaving pock marks...

Oil ring challenges... broken or worn oil rings...

Valve guides... worn...

 

See if getting pics from inside the cylinder can be helpful..?

See if oil is escaping from the base of the cylinder... any loose fasteners?

Might be two different issues..?

PP thoughts only, not a mechanic...

Best regards,

-a-

[Guest]

Clean the area really well, dry it with Isopropyl alcohol and compressed air.  Run it till it’s warm and look for a leak from the pushrod tube seal.

Clarence

[Ragsf15e]

Just now, M20Doc said:

Clean the area really well, dry it with Isopropyl alcohol and compressed air.  Run it till it’s warm and look for a leak from the pushrod tube seal.

Clarence

As doc said, for oil under a cylinder, look on top of it.  The airflow blows it down through the cooling fins.

[Janat83]

4 minutes ago, carusoam said:

First you have to have oil getting into the cylinder...

Second you have to let that oil escape the cylinder...

Third, the oil is escaping to the outside of the exhaust system...

That’s a lot of escaping...

 

oil can get to the spark plugs a few ways...

Rough cylinder walls caused by rust, and subsequent removal of the rust, leaving pock marks...

Oil ring challenges... broken or worn oil rings...

Valve guides... worn...

 

See if getting pics from inside the cylinder can be helpful..?

See if oil is escaping from the base of the cylinder... any loose fasteners?

Might be two different issues..?

PP thoughts only, not a mechanic...

Best regards,

-a-

I'll upload borescope images today, compression check was done few weeks ago and it was 75/80, also my oil consumption is 1qt every 6.8 hrs. and didn't change recently.

[Guest]

We had this same issue on a Piper Mirage, oil dripping and burning on the exhaust stub.  It turned out to be a push rod tube spring that wasn’t fully locked allowing oil to drip out at the head end not the case end.

Clarence

[DXB]

1 hour ago, Janat83 said:

I pulled out the spark plugs and It was obvious that Cylinder No.2 bottom spark plug has more oil than other spark plugs (picture 4), my mechanic said it could be from spark plug washer, he said to put new copper washer and torque it to specs and watch it, what do you guys think?

 

I think you're talking about the oil on the EXTERIOR of the bottom #2 plug in your pic?  Oil on the spark plug electrodes (part INSIDE the combustion chamber) is a common issue - it's not necessarily a big problem unless present consistently, but it has nothing to do with your oil leak.  If the oil on the exterior of the #2  bottom plug, cooling fins, and exhaust riser actually came from the #2 combustion chamber past that spark plug during operation, I suspect you'd have way bigger problems from the massive combustion leak.

Your mechanic sounds clueless.  @M20Doc's explanation sounds much more plausible, but there might be other possibilities as well.  

[A64Pilot]

That plug is oily, but does not have any evidence of burning oil, it actually looks pretty darn good to me.

‘So spark plug washer isn’t it, actually that theory is sort of nuts. So clean the engine off really well and run it uo, I like a spray can of Gunk and a cheap pressure washer myself, alcohol works great for a clean engine to start with.

‘To really find almost impossible to find leaks, spraying developer from a dye penetrant kit is excellent as it will show even a tiny amount of oil, run it’s short interval if you do that because more than a tiny bit of oil will over whelm the powder. I’d bet spray foot powder would work too.

‘ I’ve very often seen valve covers leak too, Lycoming oil tubes are an easy fix, small Continentals require you to pull the cylinder, so be thankful. 

[Shiny moose]

My vote is for pushrod seal leak or valve cover leak , but yes put in new or newly annealed copper every time you install plugs 

[Janat83]

The pushrods looked OK I couldn't spot any fresh oil on it from both sides, I did quick borescope for cylinder no. 2 you may find it in the link below

https://photos.app.goo.gl/fvMwzhmXkGVWXMpq6

The last flight I had issue with Mags switch and my right Mags wasn't firing, my mechanic said this might explain some fresh oil on the lower spark plugs due to ignition issue, but the burned oil on the outside looked not related to the last flight which was only 0.3 hours in the pattern.

Will clean the engine and try to locate the Oil leak issue. 

[DXB]

32 minutes ago, Janat83 said:

The pushrods looked OK I couldn't spot any fresh oil on it from both sides, I did quick borescope for cylinder no. 2 you may find it in the link below

https://photos.app.goo.gl/fvMwzhmXkGVWXMpq6

The last flight I had issue with Mags switch and my right Mags wasn't firing, my mechanic said this might explain some fresh oil on the lower spark plugs due to ignition issue, but the burned oil on the outside looked not related to the last flight which was only 0.3 hours in the pattern.

Will clean the engine and try to locate the Oil leak issue. 

Again, the oil on your #2 spark plug electrode provides zero insight into the source of your oil leak. Same for an oily combustion chamber on borescope exam - a completely separate issue.  Running on one mag has nothing to do with it either.  The valve cover gasket is a very common source for leaks, but the visible part of the gasket for your #2 cylinder in the pic looks quite dry.  Unless you see a part of the gasket becoming oily, that's not it either.  

[SSimpson77]

Pushrod oil tubes might look okay but under temp and vibration could be leaking a bit. Definitely not the spark plug washer idea. While your checking that pushrod tube again, check out engine breather hose. Think of all the pressure created inside cases, and if it’s slightly constricted, you might get oil blow by(into cylinders =fouled Up combustion chambers) and failed seals. The breather hose on mine was squashed to about 1/2 it’s diameter (5/8” is stock I recall) because of heat and the bend it goes through. 
 

[Guest]

The rocker cover gasket appears dry and is a silicone version, so less likely to leak if installed correctly.

Clean, dry and run till you find it.

Clarence