Seeping fuel from under the wing walk - what can it be?

[MooneyAcolyte]

Yesterday I noticed a blue liquid - presumably avgas - seeping from under the wing walk on my 1984 M20J. Where could that come from? If I am not mistaken, there is no service panel under there. Could it be a crack in the wing skin?

[Aviator]

There is a panel under the wingwalk on the M20R.  Guess how I know?

Probably one there on the J.

[Guest]

There is a tank panel under your wing walk.  It’s common for one or more screws to seep fuel at times.  You have to remove the wing walk to access and re seal the screw.

Clarence

[Jeff_S]

Been there, done that. My J also had a seeping panel in that same spot, although it didn't pool like the OP's has.  Due to the PITA factor of removing the wing walk and fixing the problem, I simply chose to keep that fuel tank at a level where it wouldn't seep.  If I did have to fill up the tanks for a trip, I always made sure to use the right tank first to get it down below seepage level.  Due to my flight profiles this was never a hardship, but if you need to keep your tanks full for some reason then it will need to be fixed.

[LANCECASPER]

2 hours ago, MooneyRookie said:

Yesterday I noticed a blue liquid - presumably avgas - seeping from under the wing walk on my 1984 M20J. Where could that come from? If I am not mistaken, there is no service panel under there. Could it be a crack in the wing skin?

 

When you remove the screw where the fuel is coming from and clean the threads with a pick, put a little Permatex aviation #3 sealant (https://www.aircraftspruce.com/catalog/eppages/permatexprod4.php) on the bottom threads about half way up the screw it will work its way up to the top as you screw it in. I let mine sit for a day before putting on the new wing walk.

[MooneyAcolyte]

8 minutes ago, LANCECASPER said:

 

When you remove the screw where the fuel is coming from and clean the threads with a pick, put a little Permatex aviation #3 sealant (https://www.aircraftspruce.com/catalog/eppages/permatexprod4.php) on the bottom threads about half way up the screw it will work its way up to the top as you screw it in. I let mine sit for a day before putting on the new wing walk.

Thanks a million. I will try that during my upcoming annual and will report back here how it went. 

[DMM]

Looks to me like its leaking from a rivet in front of  or beside the panel (i'm confused on orientation).  I can see a faint outline of the panel seam below and to the right on the leak . 

Edited December 27, 2020 by DMM

[carusoam]

Rookie,

You’re not alone in your efforts...

Somebody else is chasing the same challenge, 12 hours ahead of you!

The original thread is pretty interesting as well...  12 years ahead of you!

 

[EricJ]

9 hours ago, MooneyRookie said:

Yesterday I noticed a blue liquid - presumably avgas - seeping from under the wing walk on my 1984 M20J. Where could that come from? If I am not mistaken, there is no service panel under there. Could it be a crack in the wing skin?

Maybe it's a little bit Rorschachy, but there's a circular outline of a screw right in the middle of that.   I used a small steel pick to remove the wing walk material just from the screw head, removed the screw, and did the permatex 3 reseal.   Mine has been fine since.    You can touch up the screw with wing walk material or something similar.

 

[Skates97]

You can see the faint outline of the panel. Follow it around and find the leaking screw.

[MooneyAcolyte]

On 12/27/2020 at 1:40 PM, LANCECASPER said:

 

When you remove the screw where the fuel is coming from and clean the threads with a pick, put a little Permatex aviation #3 sealant (https://www.aircraftspruce.com/catalog/eppages/permatexprod4.php) on the bottom threads about half way up the screw it will work its way up to the top as you screw it in. I let mine sit for a day before putting on the new wing walk.

Finally had some time to follow-up on the issue and found the screw! Next step: I‘ll apply the #3 sealant. I’ll post the results .

[N201MKTurbo]

On 12/27/2020 at 2:03 PM, Skates97 said:

You can see the faint outline of the panel. Follow it around and find the leaking screw.

The screw that is leaking isn’t on the cover plate exactly. There are two aluminum angles riveted to that cover plate to reinforce it. That screw is at the end of that reinforcement angle. That is a common place to leak..

Edited January 31, 2021 by N201MKTurbo

[N201MKTurbo]

2 hours ago, MooneyRookie said:

Finally had some time to follow-up on the issue and found the screw! Next step: I‘ll apply the #3 sealant. I’ll post the results .

I think you have the wrong screw. There is another screw about 2 inches inboard and aligned with the forward edge of the cover plate. It is right in the center of your splotch.

It looks like you were scratching in the right place, you just didn’t go deep enough

Edited January 31, 2021 by N201MKTurbo

[MooneyAcolyte]

5 hours ago, N201MKTurbo said:

I think you have the wrong screw. There is another screw about 2 inches inboard and aligned with the forward edge of the cover plate. It is right in the center of your splotch.

It looks like you were scratching in the right place, you just didn’t go deep enough

Thanks. I’ll check it out.

[laytonl]

Rich is correct.  The screw where you scratched is a common leaker.  Lee

[thinwing]

put a little aircraft paint stripper to quicky uncover that screw.....perma tex gas compound didnt work for long...i finally used a good coating of flamemaster sealant on both female /male threads.Randolf wingwalk compound is thick enough to be sqeegeed with a plastic scraper arround the replaced screw.For a perfect match ,spray paint entire wing walk with flat or semi flat black.

[N201MKTurbo]

Everybody is correct that tank sealant would be a better sealant than Permatex, but you need such a tiny amount it seems crazy to buy some for that little leak. If you buy a SEMKIT it is about 2000 times more than you need, if you buy a can, you will have about 10000 times more than you need. You might ask your local mechanic if he has any you can get a little dab. There are two parts, the sealant (polysulfide compound) and the activator (manganese dioxide compound).

Interesting article about the chemistry of tank sealant:

https://apps.dtic.mil/dtic/tr/fulltext/u2/a192704.pdf

 

Edited February 4, 2021 by N201MKTurbo

[EricJ]

I noticed the other day that my wing walk shows the locations of the screws pretty readily due to a few past repairs to leaky screws and some damaged wing walk.   The screws that are away from the access panel hold a stiffener that is only in the right wing due to wing walk loads.