Oil Leak on back of IO-360-A1A

[MooneyMunnerlyn]

Hello,

 

I fly a M20E and I have an oil leak on the back of my engine. It runs down the rear interior cowling and down covering the front gear as all Mooney oil leaks do. I have somewhat located the general area of the leak through cleaning the engine and running it. But, I am not super engine savvy so I was hoping that someone could point me in a more accurate direction. I know it could be a vacuum pump, rear mounted governor, or magneto leak from what I have researched. I think it originates above the governor though. The oil filter is tight and so are the return lines. The leak runs down and covers the exhaust manifold and the orange and black lines in this photo. It seems to equate to a loss of about 1 quart every 4 hours. Here are some photos of the leak thus far (seems to come from high rear).

[Fritz1]

clean real well with mineral spirits, let dry, spray suspect area with white developer from dye penetrant system, run engine on ground for 10 min on ground at 1200 rpm, check if you see any traces of oil in the developer, if not go fly airplane for 20 min so all engine parts are at ops temperature, land airplane, pop cowl and look for oil traces, this will give you an idea where the leak is, if there are still doubts, clean everything again, spray smaller area with developer and run the engine again, no black magic, just persistence does the trick

[PT20J]

A quart every four hours is a pretty big leak.

I like @Fritz1 idea. You might try spray baby powder if you don't have the developer. 

[MikeOH]

The issue I've had is that it is VERY difficult to view the back of the engine!  Even resorting to using a borescope camera is not that effective.

[LANCECASPER]

I would be very surprised if it was leaking a quart every four hours. Are you sure some of that isn’t blow-by?

[Ragsf15e]

7 hours ago, MooneyMunnerlyn said:

Hello,

 

I fly a M20E and I have an oil leak on the back of my engine. It runs down the rear interior cowling and down covering the front gear as all Mooney oil leaks do. I have somewhat located the general area of the leak through cleaning the engine and running it. But, I am not super engine savvy so I was hoping that someone could point me in a more accurate direction. I know it could be a vacuum pump, rear mounted governor, or magneto leak from what I have researched. I think it originates above the governor though. The oil filter is tight and so are the return lines. The leak runs down and covers the exhaust manifold and the orange and black lines in this photo. It seems to equate to a loss of about 1 quart every 4 hours. Here are some photos of the leak thus far (seems to come from high rear).

What the other guys are saying nicely is that you’re not leaking a qt/4 hours.  If you were, you’d be shocked at what the bottom of the airplane looked like. You’re likely leaking a tablespoon per 4 hours, but hot oil spreads very easily and makes a big mess.  I’m not saying that your oil level doesn’t go down by a qt/4 hours.  Actually that’s not terrible, but it’s unlikely caused by a leak.  Oil can also go out the breather or through the exhaust valves.  Blow by of the rings is pretty common and will significantly increase your oil loss. These things do use some oil.

Now there’s absolutely nothing wrong with finding/fixing your leak (we all have small ones), but don’t expect it to change your oil use. Most of these engines use a qt/4-12 hours depending on cylinder type and age.

[Shadrach]

How do you know it’s on the back of the engine? The exhaust heat muff looks soaked. Oil gets everywhere  when there is airflow through the cowl. Everything must be thoroughly cleaned. When looking for the source, do not limit your focus to the rear of the engine.

[MooneyMunnerlyn]

Hey everyone quick update, 

I cleaned the engine again, ran it on the ramp at mid RPM settings to try and discover the leak. I used a UV light and I believe I located the culprit. It appears to be the bottom portion of the right mag gasket. It leaks out of the bottom and then leaks down the governor and so forth (picture shows collection on bottom of governor mounting pad). I have my A&P looking/fixing it this week. I will update you all if that was not the issue. Fingers crossed! 

[LANCECASPER]

When you put on the new mag gasket make sure that new star washers are used.

[MooneyMunnerlyn]

6 minutes ago, LANCECASPER said:

When you put on the new mag gasket make sure that new star washers are used.

Will do, thank you!