Is this a Fuel Leak ( x-post)

[AdamZ]

The other day a friend and I were supposed to do a Angel Flight. I had the FBO top off the tanks on the Lance the night before to save time in the morning and to prevent condensation ( we were due for our first frost)We got to the field around 7:00 A.M. and waited for the sun to help melt the frost on the wings ( can't use glycol anymore, no way to recapture it) anyway about 15 min later I notice a big blue stain under the wing. I have seen this before near the strainer valves and the overflow vents, its the blue dye in 100LL. This stain however was in the middle of the wing and not connected to the strainer valve or an overflow vent. Then I notice a drip drip drip comming from a little "button" under the wing a bit outboard from the gear, I'm thinking is this frost melt, I don't know so I stick my fingers in the drip and smell it. Yikes its fuel. I then get my strainer and put it under the drip collect an inch or so and sure enough its blue.
I spoke to one of the CFIs and he said perhaps it was expansion out the vent or overfill. problem is it was filled the night before and it was still pretty cold also the drip was not near a vent tube which is much closer to the gear in the lance ( and inboard from the leak) The CFI concurrs its a fuel leak. He said when he removed the button the fuel cam out and went down the wing rather than the slow drip when he put it back it reverted to a slow drip. and we scrub the mission. I call the plane owner and give him the bad news. Later that day a few hours later the owner stops by looks at it and thinks its a fuel leak. The FBO owner then stops in and says its not a leak but over fill. ( At this point the owner of the Lance is ready to sell it he is so frustrated expensive few months for him)
I went back on Sunday to do some other business at the airport and check out the Lance. Now its bone dry and the tank is full to within an inch of the top, no dripping.
I spoke with the owner of the Lance quite a bit about it and he put the plane in the shop yesterday to have the A&P check it out. Today A&P says No Leak, its normal just overflow. The A&P seems to know his stuff but I'm sitting her scratching my head trying to figure out where the hell this fuel was comming from. It wasn't coming out a vent tube it wasnt comming from a strainer valve, just this little metal button about the size of a dime that you can pop in and out of the wing. Any ideas here. I'd really love to figure this out! Is there someother venting source inside the wing? Thanks for the input.

 

[Let'sgoflying!]

How could it not be a leak if there is fuel inside the wing? Does the POH or service manual say anywhere, "Fuel floating around inside the wing may result from overfilling the tank, and this is normal" or something like that?

Sounds like a leak near the top of the tank, could even be the filler neck.

 

[wsuffa]

This falls into the category of "know the plane".

On my plane there are two fuel vents on each tank. One vents external to the fuselage at the tip of the tank, the other vents under the belly. If you overfill the tanks (or you park on a tilt with the fuel selector in both and the check-valves are not fully closed), you can see fuel seepage at the bottom of the belly.

I don't know the Lance at all. Could be a similar situation, could be a leak at the top of the tank.

My rule of thumbs are 1) to leave just a slight amount of expansion space when fueling unless I am planning an immediate takeoff, and 2) make sure the fuel selector is in the off position when parked.