Leaking near fuel cap

[Johan]

I have noticed a fuel vapor leak near the fuel tank cap seal (attached). It has been there for two years already but it got worse over the last winter.

 

What material is used as a sealant around the cap?
Does anyone have a suggestion how to fix this/what the source if it might be (some kind of gasket)?

 

Thanks

[Roger Lee]

This is just an epoxy that FD uses. I forget the brand I have used a small bit Dremel tool to remove the epoxy and then just epoxy it back in place. Just make sure the epoxy you use is compatible with fuel and ethanol. I just set the fuel cap insert in place and just used a tongue depressor or popsicle stick to let it flow around the edge. When it is just a tad above level just quit and let it set for a day or so.

 

Just a side note. Youy can Dremel all the way down to a protrusion under the outer layer of epoxy. Leave the insert in place and just replace that epoxy you removed. When you start to Dremel down to remove some of the epoxy around the edges you will see where it kind of bottoms out. 

 

takes alittle time to Dremel out the old epoxy, but is easy enough to do.

[Johan]

Thanks a lot, Roger!

[Runtoeat]

Roger, are you saying you 1st remove the outer part of the filler from the wing, then set this back into the wing, leave it loose, apply the Epoflex and let this flow down around the filler, then screw the filler in? Or, are you saying you just remove the old Epoflex with a dremel and apply new Epoflex without removing the filler?

[Roger Lee]

I was talking about two ways to do it. If it's loose then yank it all together andd then you have to epoxy the whole thing. If it's tight with just a tiny seep then mill out around the edges and just

re-pour  and seal down to where you stopped Dremeling.

[Runtoeat]

Thanks Roger. Sending you an email.

[Roger Lee]

Oh No, I knew I shouldn't have answered that question. 

[Runtoeat]

He, he.  Just comparing notes with you.

[Johan]

I am ready to fix this soon.
One more question though - do you think drilling out the problematic spot and filling it up with the new compatible epoxy would be enough in my case?

I don't know how exactly the fuel tank is fitted to the wing and the cap. Doesn't the problem look like leaking gasket KA7020053 which needs to be replaced and removing KA7020052 part completely would be needed to get access to it? 

Thanks for suggestion.

[Runtoeat]

zvlcxgme.  If you might be able to provide a simple first name, I know, personally, I would really appreciate it.  My CTSW was repaired and those parts you call out in your post are correct for needing removal.  One other consideration is that the 4 attaching screws are epoxied in and these are very hard to remove.  You may end up stripping out the hex head on these and if you do, you may need to drill these out to remove them.  I recommend that you call Flight Design (Arian) and buy some Epoflex to reseal the filler (KA7020052) after this has been reinstalled.  Arian should be able to provide you with directions for doing this repair.

[Mike Koerner]

Dick,

I have leakage around my filler fittings too. In fact, mine look worse than zvl's. 

If KA7020053 is an elastimeric (rubber) seal that fits under the filler fitting as shown in the drawing, and the 4 screws are in blind holes, why would you need Epoflex (or any other sealant)?

Mike Koerner

[Runtoeat]

Hi Mike.  The factory seal that was in my filler and the new one sent to me appears to be treated a paper gasket.  It appeared that Halomar, or some similar blue colored sealant was used in addition to the gasket.  The gasket and blue sealant were compromised and fuel had made it's way past the gasket, traveled up thru the Epoflex and then was carried back to the trailing edge of the wing by airflow.  The Epoflex was discolored by the fuel leak on my filler and I imagine this is the case on all of those who have leaks.  Long story short, my filler was removed and had to be destroyed in the process.  A new aluminum filler was installed.  This ended up leaking up thru the new paper gasket and past the new Epoflex again.  This new filler was removed and a new gasket was installed.  1 of the 4 screws was stripped and it was no longer in a blind hole but was now exposed to the fuel in the tank.  After some good repairs done by my mechanic, all is good now.  If one repairs this area, perhaps one might consider fashioning a gasket using a different material than the factory paper gasket and using a sealant, perhaps proseal. 

 

Roger, this is the note I sent you but didn't get a reply.  No surprise since I don't know how you find time to sleep with all you do.   I'd be interested in your comments and comments by the other experts on our forum regarding repair of this area.

[Mike Koerner]

Ah, the old bogus gasket trick.

Thanks for the description Dick, but after reading of your trials I'm inclined to just let mine leak.

Mike Koerner 

[Runtoeat]

Mike, if you get the 4 screws out and these are not stripped, you have the major work done.  You should be able to then pop out the filler from the epoxy sealant.  It sounds like you've had experience with gaskets and so should be able to come up with a better one than the factory.  I have no experience with Hylomar sealant but Roger Lee says this is the only sealant to be used.  My mechanic doesn't use Hylomar and uses a different aviation sealant.