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Fuel leak on left wing tank M20J

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I just faced fuel leak on the left wing tank : started to repair as you will see on the attached pictures

There was a micro hole at the junction of two metal sheets fixed by a spar, made the repair today, will let the glue material dry during the week end and reinstall the plates by next Monday, i will let you know if it will be fixed. Had good mechanic and advice of an experienced expert in metal plane assembly.

if any of you has similar experience and comments : welcome before i do the reassembly on Monday

Thanks in advance

Philip from France3F1F5F94-779C-4E50-BF19-505A343AA5A3.thumb.jpeg.c8f223dda2798b3ef728c7504b6f615f.jpeg






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  • 2 weeks later...

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Hello Philip, I have a Mooney Ovation and a bay in the left wing is leaking. How did you identify the exact location where you needed to add the sealant?  My paint color is the same as your Mooney!  043D2E49-489C-4D44-8B75-7B41CCD94597.thumb.jpeg.f4147132106600eae0525f1d2b94f0b7.jpeg

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There is no procedure in the service manual that allows putting sealant on top of old sealant. 

The proper procedure is to remove the old sealant in the area of the leak down to bare metal and apply new sealant per the service manual.

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I am facing a similar issue, classified as "heavy seep" per Mooney Mx Manual, in the very same spots as you mentioned, plus a few more locations. The owner of the plane has a slot scheduled with a resealing shop later this year, but I'm not sure if the plane will hold up until then. As an A&P, I'm heavily considering doing some local repairs myself, but the Mx Manual doesn't seem to mention any precautions on purging out the wing of vapors. Maybe I'm overly paranoid, but having heard of some horror stories, the last thing I want is a wing exploding in my face.

For those that did this procedure, what kind of steps did you take after draining out the fuel but before working inside the tanks? In addition, how difficult is it to remove the inspection cover screws considering they're likely covered with sealant?

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Be assured, that every step to avoid a fuel fire is incredibly important...

It may not get mentioned in the manuals anywhere...

But fuel fires and Mooneys don’t get along very well...

Vapors and confined spaces are bad...

Vapors that travel across the floor are bad... the heater is not that far away, and may even supply an open flame...

Fuel that leaks out of a screw hole onto the electric screw driver of a new mechanic are really bad...

When reading about resealing... you may see a lot of how the tank gets emptied and washed out...

Static electricity this time of year is prevalent...

There is plenty of advice written around here on best practices used for grounding and best containers to be used to empty the tanks...

... and how many fire extinguishers are around...

yes, my home drome had a bad experience after a Mooney fuel fire... 


You can’t be too careful...

PP thoughts not a mechanic...

Best regards,


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