Oil leak - guess the source!

[JamesMooney]

Time for one of MS'ers favorite pastimes.... guess the source of the oil.

Discovered ~5 minutes after flight. Only on the left side of nose wheel. A 'few' drops (4-8 droplets?). It was fairly green-ish colored to the touch (not black). No leak/signs of oil observed in pre-flight. Oil steady at 6 qts - none extra added before flight. No oil on belly or anywhere else. This was the ~8th flight (15 hrs) after prop gov O/H and engine IRAN'd and re-installed. Oil on tire wasn't seen in any of the previous flights.

With A&P this week for oil change - and to hunt for the source.

 

[Ragsf15e]

Easy.  Normal fuel drips out the sniffle valve after shutdown!

with Anthony’s standard disclaimer… not an A&P, etc etc.

[RLCarter]

18 minutes ago, Ragsf15e said:

Easy.  Normal fuel drips out the sniffle valve after shutdown!

with Anthony’s standard disclaimer… not an A&P, etc etc.

But it’s an oil (clean oil) leak  not fuel 

[Ragsf15e]

Just now, RLCarter said:

But it’s an oil (clean oil) leak  not fuel 

Well you said greenish, and by the time my fuel drips out the sniffle onto my tire, that’s about how it looks.  
 

The tire is a common place to get them, however, that drip occurred after shutdown (wheel wasn’t turning).   Directly above that spot should be your fuel pump drain and sniffle drain. Most likely one of those.  I’d keep an eye on it and see exactly what’s coming out those two tubes.

[JamesMooney]

Ok so we have....

1. Sniffle valve 

2. Fuel pump drain (o/h'd fuel system installed 12 hours ago)

3. Unknown leak of clean oil

What about prop governor? Any chance there's oil coming off that? Would it only happen at the END of the flight?

[Ragsf15e]

And just to make it tougher, I’ve had oil come out both the sniffle and fuel pump drain.  One was a bad fuel pump leaking oil.  The sniffle oil was from a cylinder with some issues… wobbling valve?  Bad valves?  Oily cylinder?  Anyway, there was some oil in the intake manifold that use to drip after each sortie.  OH cylinder fixed that one.

I know this is a fresh engine, so I really think it’s fuel, maybe mixed with a little something?

[carusoam]

1) Grab a roll of white paper towel…

2) Dab the drips with the towel…

3) Observe what the drips do on or in the towel….

4) oil has a tendency to be golden brown, and will spread out… leaving dirt behind…

5) Fuel… spreads even faster.  If it was concentrated by evaporation it will have deep blue parts

6) Grease… is usually so thick it doesn’t drip…

7) Take some pics of the towel…

PP thoughts only, not a mechanic…

Best regards,

-a-

[N201MKTurbo]

It indicates the engine isn’t out of oil. It’s a good thing.

Seriously, there is no way to tell from those drips. Any leak in the engine will make its way to there. You will need to pull the cowl and look around.

[jaylw314]

I gotta say, that just looks like oil from the breather tube.  I don't know how the drains for the F's are arranged, but in the J the fuel pump overflow, intake manifold drain and crankcase breather are all bundled together out the left cowl flap.  If there is oil dripping from the breather tube, with the right breeze, it drips on the tire.  Likewise if there's any blue fuel dye on the end of the intake manifold drain, the oil can mix with it.  I'd also point out that yellow oil + blue fuel dye = green crap.

Edited June 16, 2021 by jaylw314

[jlunseth]

There are several things it could be. That is what a leaking quick drain looks like when it is starting to fail, but there are other things, since oil tends to cling to a surface and run before it has to drip. Quick drain leak is clean oil. 

[neilpilot]

When I observed this after a flight, it turned out to be a loose mag that had recently been installed by a well known MSC.

[mike_elliott]

6 hours ago, N201MKTurbo said:

It indicates the engine isn’t out of oil. It’s a good thing.

Seriously, there is no way to tell from those drips. Any leak in the engine will make its way to there. You will need to pull the cowl and look around.

Exactly, From most expensive to least cause, It could be anything from a cracked case to a oil filler tube O ring. Might I suggest a complete cleaning of the engine then use some magnaflux developer around the suspected areas based on your Mark I eyeball locater. Run the engine hard for a few minutes decowled, and the leak origination point will be obvious.

CB's can use spray foot powder if they dont want to buy the proper stuff...

[bob865]

Look just like the oil leak I had when my prop governor started leaking.  Same place and everything.  There s a "shelf" in there that sits under the governor.  it's either part of the landing gear strut or a foot well for the rudder pedals.  That's were it would collect on mine and not drip down until enough had collected.  Made it appear to be an intermittent leak.

[JamesMooney]

Thanks all. I'm intrigued by the governor theory. This was an o/h'd governor (and after all, don't things always seem to break or be wonky right after major work on them!). Since getting the plane back, I've noticed it doesn't cycle on the runup at 2000 RPM - but does cycle well at 2200 RPM. My A&Ps initial thinking was that this isn't unusual - has seen plenty of 3-blade prop Mooneys that prefer to cycle in runup at 2100-2200 RPM. But it got me wondering if there was something amiss with the o/h'd governor.

I've sent all these ideas to my A&P who has the plane today... Hoping to report back soon. (But keep the ideas coming! Thanks!)

[Hank]

5 hours ago, FlyingCanuck said:

Thanks all. I'm intrigued by the governor theory. This was an o/h'd governor (and after all, don't things always seem to break or be wonky right after major work on them!). Since getting the plane back, I've noticed it doesn't cycle on the runup at 2000 RPM - but does cycle well at 2200 RPM. My A&Ps initial thinking was that this isn't unusual - has seen plenty of 3-blade prop Mooneys that prefer to cycle in runup at 2100-2200 RPM. But it got me wondering if there was something amiss with the o/h'd governor.

The 3-blade Hartzell on my C has been cycling well at 1700 RPM since I bought her in 2007. Then again, I have the simple O-360, not your fancy IO model.

Let us know what you find!

[JamesMooney]

So the preliminary answer is in... Looks like the culprit was not one, but three sources. (1) Sniffle valve may have had a small bit of debris in it leading to a drip; (2) an engine hose had come loose (recall: this engine was just re-installed 12ish hours ago); and (3) a nut had come loose.

Those three things addressed - no oil noticed in the ground test afterward.

Knock on wood that clears things up for now! Thanks to M/S for the inputs here - they were helpful!!!

[carusoam]

Great follow-up FC!

What nut tried to get away?

Best regards,

-a-

[Ragsf15e]

Also, the sniffle valve is supposed to leak.  That’s why it’s there.  When the engine is running its sucked closed/sealed, but when the engine isn’t running, it opens to let the intake manifold drain.  Usually a few drops of fuel after shutdown.

[Boilermonkey]

Check the torque on the rocker cover screws.  If you have silicon gaskets, be sure to not over tighten....I've found a lot of APs don't have the latest SB and apply too much torque causing the gasket to mushroom out and cease leaks.  WE chased that problem for months with our old C model.

[MBDiagMan]

On 6/15/2021 at 11:47 AM, Ragsf15e said:

Easy.  Normal fuel drips out the sniffle valve after shutdown!

with Anthony’s standard disclaimer… not an A&P, etc etc.

Maybe you’re right but it doesn’t look like fuel to me.

[Yetti]

I vote some oil was spilt during the oil change.

[JamesMooney]

Just now, Yetti said:

I vote some oil was spilt during the oil change.

I'd love that - but the oil change was 12 hours and 8 flights previously.... Still viable scenario?

[JamesMooney]

1 hour ago, MBDiagMan said:

Maybe you’re right but it doesn’t look like fuel to me.

One thought was it was oil and fuel mixed - fuel from the sniffle and maybe some oil from the loose engine hose? 

[Yetti]

2 hours ago, FlyingCanuck said:

I'd love that - but the oil change was 12 hours and 8 flights previously.... Still viable scenario?

There are a couple of places it can sit before it falls out the bottom.  get a flashlight.