Hunting oil leaks

[AndreiC]

My 1970 E (IO360) has developed what seems to be two unrelated oil leaks. One I think I understand -- I am pretty certain comes from the left mag, where it mates to the accessory case. The other one is more confusing. While diagnosing today the first leak, I cleaned the engine as best I could, then ran it for 5 minutes at settings between 1400 and 1800 rpm, with just the top cowling on (no cheeks). The strange thing is that at the end of it I had a clear oil streak (as if one big drop dripped down) along the intake tube for the #2 cylinder (left front). I then checked the left cheek, and, sure enough, there were multiple streaks of oil in that same area (front side).

Where could this second leak be from? I can't imagine oil being brought forward from the magneto all the way to the intake, so my guess is this is a separate leak. My first thought was that maybe It is the valve cover gasket, but from what I could tell it was dry. Also the oil return tube seemed to be dry,. Is there oil at the mating of the intake tube and the cylinder? Can there be an oil leak from there?

Thanks,

Andrei.

[N201MKTurbo]

Some times if you have a leaking push rod tube it will run down the fins and then down the intake.

[AndreiC]

51 minutes ago, N201MKTurbo said:

Some times if you have a leaking push rod tube it will run down the fins and then down the intake.

Oh, ok, I'll check that next time I go.

[Yetti]

take a flashlight and see if you see any drips hanging when cool.   valve covers, drainback tubes are starters.

[Pinecone]

UV Dye.

Clean engine, add 1/2 ounce to the crankcase.  Run for 2 minutes.

In hangar, look with UV flashlight.  Oil leaks are very visible.

[Sabremech]

1 hour ago, Pinecone said:

UV Dye.

Clean engine, add 1/2 ounce to the crankcase.  Run for 2 minutes.

In hangar, look with UV flashlight.  Oil leaks are very visible.

I was chasing an oil leak on a J model last fall and thought of UV dye until I saw the price. If memory serves me right, the minimum quantity was a gallon and I’d never use that in my life time. I didn’t search for every possible source so maybe it could be found cheaper and in a smaller quantity.

ultimately, we found it using Magnaflux developer.

David

[Fly Boomer]

10 hours ago, AndreiC said:

Oh, ok, I'll check that next time I go.

If you don't have UV dye, or would rather not buy a large quantity, you can try just using a UV flashlight and UV glasses in a darkened hangar.  Engine oil is mildly phosphorescent (maybe it is fluorescent?) under UV light.  Okay, I will just say luminescent, and avoid the subtle differences.

[Greg Ellis]

47 minutes ago, Sabremech said:

I was chasing an oil leak on a J model last fall and thought of UV dye until I saw the price. If memory serves me right, the minimum quantity was a gallon and I’d never use that in my life time. I didn’t search for every possible source so maybe it could be found cheaper and in a smaller quantity.

ultimately, we found it using Magnaflux developer.

David

They have lots on Amazon at very small quantities.  This one for instance... Amazon.com: InterDynamics Certified Auto Pro Oil and Fuel System UV Dye Leak Detection for Cars & Trucks & More, 1 Oz, 374CS, Universal : Automotive

As well as others in small quantities.

[Fritz1]

clean real well, dust with baby powder or dye penetrant developer, fly airplane, pop cowl and look for traces, some leaks only leak when the engine comes to operating temperature all around, patience and persistence kills all leaks

[MikeOH]

6 hours ago, Pinecone said:

UV Dye.

Clean engine, add 1/2 ounce to the crankcase.  Run for 2 minutes.

In hangar, look with UV flashlight.  Oil leaks are very visible.

I have found it VERY difficult to illuminate and get a line of sight to the back of the engine...all the stuff on the accessory case.  Just sayin'