Leaking fuel tank

[JoshMan]

Hey, guys.  I have a quick question about fuel tanks.  I recently bought a 1969 M20E.  Tanks have not been resealed since then.  I filled both tanks up for the first time and noticed the smell of gas when I was on final.  There was a noticeable leak under the left wing.  I am scheduled to take the plane up to  Minnesota for resealing of both tanks in January, but am wondering how to approach the problem in the interim.  I filled the left tank with 10 gallons and there was no leak or odor.  I filled it with 15 gallons last night and the hangar and cockpit smell like fuel.  I assume this is unsafe to fly? How have you guys managed the leaking fuel issue? Thanks a lot

 

Josh

[Mooneymite]

Don't  assume it's  a tank unless the blue stains lead you there.  There are short legths of fuel line connecting the tank lines to the plane which sometimes leak and make a stink inside the plane.  This is easy to check behind the sidewalls by the two front seats.

I'd  check those connections first if I smelled fuel.

[JoshMan]

Thanks, there is definitely a leak under left tank but I agree a leaking line makes sense, too.  Unsafe to fly with a leak? Can it wait until January or should I pursue fixing earlier?

[neilpilot]

In addition to fuel lines, the fuel sender gasket has also been known to leak.  Can you get by safely by ferrying the plane on the right tank?

[Tony Armour]

24 minutes ago, JoshMan said:

Thanks, there is definitely a leak under left tank but I agree a leaking line makes sense, too.  Unsafe to fly with a leak? Can it wait until January or should I pursue fixing earlier?

I think to determine that, you need to lay eyes on it. Maybe pull that side panel off. There is a chart showing external Mooney leaks...kind of a go no go. Not too concerned about safety if it's only leaking out under the wing.

Run off one tank unless the other is needed for the journey...fill as needed.

[carusoam]

Don't fly with known unknowns... 

Fuel line and fuel level sensor can leak soaking the rug behind your seat.  It might be as simple as tightening some hardware.

What fire extinguisher do you have on board? Is it in reach? (Makes you think doesn't it?)

Fuel fires are awful.

Best regards,

-a-

 

[lamont337]

Leak classification page from the manual attached:

 

Edited October 22, 2016 by lamont337
Corrected pic

[lamont337]

And here is a view of where the fuel line comes in from the left tank. Check this area on both sides if you smell fumes in the cabin.

[Yetti]

Some times the tanks leak at the top so it may not leak if you leave the last 10 gallons out.   There is an inspection plate on the leading edge of the wing on the underside about in line with the gas cap.  You may remove that and see if you can see something like blue stains.  Note that the manual says leaks into the wing are a non happy situation to fly with.   Take pictures of where the staining is and post them.

[carusoam]

Great photo, Lamont!

the short piece of rubber hose is the fuel line.  It gets swollen and hard before it cracks and leaks.  Easy enough to get swapped out.  If it is original, Swap it out just because you are in there...

The lone wire coming out of the tank is the FL sensor.  The seal around that plate is known to leak.  Getting a new polymer gasket is the usual fix for that.  The old cork seal is...  old and cork!  

PP challenges I had with my 65C.

Best regards,

-a-

[MyNameIsNobody]

Been there.  The sealant at the top of the tanks is more prone to drying out and leaking.  Told this is because fuel cools sealant that is exposed in a hot summer tank over decades.  Deteriorates and weeps.  NOT a safety of flight, but if seap is running as shown in photo...needs re-sealed.  I would store for years with minimal fuel...or I would lose it, over time.  I had fuel smell in cabin with fuel sender seal deterioration...wet rear carpets...had ALL the fun.  Minnesota got me squared away.  Paul will solve your problem and the constant dread will be just a memory.  Not cheap, but leaking fuel in an airplane.  NOT a good feeling...Hope resolution is smooth and only causes some pain to pocketbook...like all things aviation.

Great photos and discussion in this thread.