Replacing Fuel Sump Fitting

[Rick_Luck]

I have to replace a fuel sump fitting sometime in the near future. I have the new one on hand but the old one has quit dripping for the time being. I have 2 questions for those of you with experience in replacing these.

#1. It doesn't look like there's a place for a "backing wrench" to help support the flange that the sump fitting is screwed into while you'e torquing on the old fitting to remove it - or tightening the new fitting in for that matter. In searching the posts, I see where one person attributed his leaky fitting flange to having to remove a sump fitting multiple times - causing a leak betweent the flange and the tank skin. I suppose I could use a very small pipe wrench that I sometimes use for jobs like this but I really don't want to wreck the paint or scratch the metal tank flange. The mini-pipe wrench might also be too thick to get between the sump fitting and the flange. The flange looks like it is attached to the tank with plenty of rivets, but is some kind of backing wrench still a good idea?

#2. Is it OK to use some teflon tape on the threads of the new fitting or should I be using nothing at all or another product as a thread lubricant/sealant when installing the new fitting?

Thanks for the information & help.

[TShort]

Dunno about #1 ... I think the flange is riveted with 6 -3 rivets (I'm getting ready to do my tanks now).

My buddy who is an old timer A&P/IA puts a small amount of teflon pipe tape on the drain ... I helped him replace one in his C-140 a few weeks ago. Just don't put it all the way to the end so it won't get into the tank.

Thomas
-8 wings

[Mel]

Do not use teflon tape on any fuel fitting! Use a small amount of Permatex "form-a-gasket". This sealer has been approved and used for aviation products since I was a kid. (And that was a loooong time ago.)
Mel...DAR, A&P, Tech Cnslr, Flt Advsr

[TShort]

I thought I had heard that before ... wasn't sure it applied to things like the drain that aren't "in line" in the fuel system.


Thomas
-8 wings

[dan]

There's also EZ-Turn, which is "fuelube". http://www.aircraftspruce.com/catalo...ezturnlube.php I personally prefer it over the black Permatex gunk, at least for fuel fittings (just my opinion).

But anyway, before you replace the whole drain, have you tried replacing the 18 cent O ring?
http://www.aircraftspruce.com/catalo...ges/safair.php P/N MS29513-006. I've replaced mine before...usually just cleaning the crud out of the drain fixes any dripping (assuming the drips are coming from the drain and not the fitting threads). When the O ring dries out and cracks it causes dripping. I'd rather spend 18 cents than 9 bucks. FWIW, I carry these O rings (among several other types) in my tool bag.

Also, in answer to your question about using a backing wrench...I don't use one on those fuel drains. Just make sure you're not applying any "vertical" to the wrench so it doesn't try to twist/buckle the fuel tank skin. And it shouldn't take all that much torque. You got the fitting in there in the first place, you can get it out and back in.