Another red cube leak

[BillL]

I have been fondling that red cube for a couple of days trying to figure out where it will go and thinking about the NPT seal. Information in this thread has undoubtedly saved me hours of headaches.

It is sad that the threads on such a beautifully made part are not more precise. I agree with Tom, a good straight thread and o-ring seal would be more fitting of such a part.

Happily I passed on the EzTurn and decided for my tried and true Permatex Aviation #3. (also confirmed after some research on VAF)

My donation to VAF saves me lots of time! Thanks VAF!

[Rupester]

...that the EII people have a "passive recall" (their terminology) on certain serial #s on the red cube. They were non-specific about the basis for said passive recall. I'm willing to bet it's a batch of red cubes with defective threads. The passive recall essentially means they remain passive, while we chase leaks. ( Sorry about the sarcasm there, but I'm hugely irritated by the leakage on that device; it's cost me 6 to 8 hrs flying time) If you call them and you have the right serial #, they will apparently replace your red cube.
Additional info ... I ended up installing the outlet fitting a THIRD time with a hardening thread sealant. That finally cured the incessant leakage. The sealant directions said to wait 48 hrs before subjecting the joint to any pressure ... which I did.
Thank heavens 100LL has blue dye in it. Without the traces of blue on the white engine mount and white cowl, I never would have found the source of the problem.

[RV10Rob]

Interesting about the "passive recall". If there's a problem, they should really be proactive about alerting people, since it could be dangerous.

I fixed the leak at the "in" side of the red cube back in October with some Permatex #2, and it's still holding up. I'd planned on fixing the "out" side at annual, which is now, and sure enough it's already leaking. Just did the same Permatex fix on that side, so hopefully I'm done messing with this.

Moral of the story: look for leaks with the red cube, and even though it shouldn't be necessary with a tapered fitting, use a good sealant.

-Rob

[pierre smith]

You guys flying RV-10's need to be super vigilant about leaks in the tunnel area!

Some of you may not remember Todd Sweezey's explosion in the cockpit of his -10 a few years ago. It blew out the windows and the left tank OFF the airplane, which subsequently was destroyed by fire.

Best,

[TS Flightlines]

Was NOT a pretty sight. Very glad Todd and daughter recovered.
Tom

[bird]

Two thumbs up for permatex #2

It is a true and proven sealant


Bird

[N427EF]

That Fuel Leak I had on my red cube had me concerned enough to
add one of these Fuel Fume Detectors. I have had no leaks or fuel smells
since gooping up both fitting threads with Pro Seal.



http://www.westmarine.com/webapp/wcs...FSHZQgodIFQAuA

[Skyflyer]

Several posts have ask if tapered NPT threads should seal without a sealant. The answer is not necessarily, as a bit of googling will show. NPT threads require the use of a sealant while NPTF do not. Fuel Lube is not a sealant but it might be a satisfactory lubricant with NPTF threads. With NPT threads, which we usually encounter, I always use a PTFE pipe dope/sealant and to date have never had a leak.

[RV10Rob]

Another update: it started leaking again at the end of my big trip (though I wasn?t able to find it until I was home). I don?t know whether I didn?t get the threads clean enough when I reinstalled the fittings with Permatex, but decided given the risk to safety and time/effort to keep messing around with this, I?d just start over. One new fuel sender and two new fittings later, hopefully I?m done.

-Rob

[rocketbob]

The threads on the red cubes are not deep enough. I have a 1/4" NPT tap I use on them which will correct the threads. I have a set of taps for this purpose, ground down NPT taps so they are bottoming taps.