Wild weather swing - sudden fuel leak

[Matt Ward]

Hey there, hoping you guys can help.  1966 M20E with no known history fuel leaks. I've not seen any blue marks, noticed any fuel loss, etc.

Monday of this week it was 75 degrees in Denver.  I had the fuel truck top off my mains - I have Monroy aux tanks too.  The truck typically gets the tanks *very* full which I'm sure they did this time too.  Fast forward to Sat and Sun.  48 hours of snow and temps in the mid teens.  I went to check on the plane today and brush the snow off - it's on the ramp but under covers.  There was a stream of fuel coming from the right wing near what I think is the fuel vent hole - although I truly haven't been able to confirm what it is.

Pictures and video below.

My assumption is this is related to the likely overfill of the tanks and the sudden and significant temp drop.  But I don't really know why that would be so I thought I'd throw it out to the Mooney hive mind.  Thanks for anything you can offer!

-Matt

 

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[DonMuncy]

If it was filled to the very brim when very cold, if it warmed up some, the fuel would expand, perhaps pushing the excess out the overflow. That does not sound like what you are describing, but worthy of some thought.

[Matt Ward]

1 minute ago, DonMuncy said:

If it was filled to the very brim when very cold, if it warmed up some, the fuel would expand, perhaps pushing the excess out the overflow. That does not sound like what you are describing, but worthy of some thought.

Right, it’s the opposite. Filled when warm and leaking when cold. 

[kortopates]

None of those pict are anywhere near the fuel tank vent which is outboard of the wing tank. I can't be sure of what I am looking at but the third picture looks like a rear inspection panel behind the tank near the fuselage and behind the gear. The dark stains indicate this isn't a new leak. Anyway it looks like this isn't the source of the leak, but it looks like its leaking somewhere at the rear of the tank and just draining out at that inspection plate area. Given the dark staining I wouldn't suspect it had anything to do with your recent fill up in Denver but probably just getting bad enough that you noticed it now.  

[carusoam]

Fuel pouring out a drain hole…

Indicates there is something leaking inside the wing…

Could be as simple as a seal on fuel level sensor, outboard, if you have one…

 

Note, it is really hard to over fill a Mooney enough to have it get to the fuel vents… they are pretty far up hill in most cases…. And require being parked on a slanted surface…

We have more dihedral than a Cessna… that is really easy to fill to where the vents are…. 

PP thoughts only…

Best regards,

-a-

[LANCECASPER]

On 3/6/2022 at 6:50 PM, Matt Ward said:

Hey there, hoping you guys can help.  1966 M20E with no known history fuel leaks. I've not seen any blue marks, noticed any fuel loss, etc.

There are two kinds of fuel tanks in Mooneys: (1) Those that currently leak and (2) those that will leak in the future. It's just something to plan for.

Sometimes a single leak or two can be patched by someone that knows how to chase down leaks, but eventually the tanks need to be stripped and re-sealed.

[N9656G]

Hmmm... I have heard to not eat yellow snow...BUT THAT BLUE SNOW LOOKS AMZING TO TRY!

[DXB]

Agree everything points to this being an ongoing issue.  I suspect the dark blue paint was masking the stains previously, and the previously small amount dripping on the ramp asphalt would evaporate too fast for you to see it.  The snow on the other hand accentuates it beautifully.