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weeping BNC

miyu1975

miyu1975

Well Known Member
So I have been having problems with my left tank fuel indicator not working for a while now. I went ahead and ordered a new dynon compacitance converter figuring that the one had was bad. I pulled off the converter from the bnc on fuel tank and found fuel inside and around the bnc. Further investigation showed what I believe to be a small leak around the outer edge of the bnc.
:(
Other than pile on some more proseal around the bnc how may I fix this? Trying to avoid pulling the tank off completely if I can.
 
Except I used proseal on the access cover. How difficult will that be to remove with the proseal?
 
Ryan,
Use a tongue depressor or Popsicle stick with one edge sharpened on your belt sander. You want it to look like a gasket scraper. Use this improvised tool to remove the access cover. A plastic paint scraper [available at Home Depot or Lowes] will also work and not damage the tank or cover.
Are you sure that the leak is coming from the circumference of the BNC connector? Did you use the cheapo "Made in China" BNC connector supplied with the Vans kit?
Charlie
 
Yes, for sure coming from the BNC circumference. I wiped it clean and then watched a little more fuel ooze out...(the tank is fuel right now)

I did use the "cheapo BNC" provided by Vans. Didn't know any better at the time. I suppose I could be better a better BNC from Stein?
 
Not sure how it is leaking, I recall putting gobs of proseal on the inside...even have a pic..

https://picasaweb.google.com/miyuwedding/RV7Pics#5360727401586361986


RV7Pics
 
Better BNC?

I am right at that stage, and installing cap senders in my tanks. Can anyone tell me what this "better BNC connector" is and why? Seems like anytime I order something from a vendor, I always come up with some other little thing I should have ordered... Since I just placed an order with Stein yesterday, it only makes sense..:(
 
The only leak I had when building my tanks was right through the center of the BNC connector. This is the pin where you solder the wire, I did not think to pro seal that little area. I believe there are leak proof connectors available, but since I think you should cover the entire thing with pro seal anyway I guess it doesn't matter.
 
ppilotmike said:
I am right at that stage, and installing cap senders in my tanks. Can anyone tell me what this "better BNC connector" is and why? Seems like anytime I order something from a vendor, I always come up with some other little thing I should have ordered... Since I just placed an order with Stein yesterday, it only makes sense..:(
Click to expand...

Mike,
Are you trying to tell us that "Murphy" lives in your back pocket?? :D That happens to all of us. You want to use an Amphenol [made in USA] brand Part # 31-236 RFX for the male half & # 31-326 for the female. The Chinese units sold with Vans kit are not designed to be liquid tight.
I'm going to contact Ryan & you off list with more info. You can buy these at your local electronics supply store, NOT Radio Shack [all import stuff]. Downside to buying locally, is that you might have to buy a "pack" of them. I'm sure that Stein can supply them, as well.
Charlie
 
wire seeping

I'm new at this tank sealing ordeal, being only half way done. But be sure fuel is coming from around the BNC connector fitting. I know a couple guys who had leaky BNC connectors from not sealing the sender plate - connector - wire joint properly and fuel seeped through the wire / insulation from the sender plate to the BNC connector... Hence their hershy kiss gob of pro seal was prety much useless. Just a thought from a guy who is building his tanks and absolutely paranoid about leaks of any kind.... Iv'e compile a list of reported leaks & trying to avoid them all :eek:
 
The leak could very well be coming thru the hole and not the edge...hard to tell. Either way I have find a way to remove the cover and replace the bnc. I did order some of the bnc that charlie recommended.
 
My plan was to use "low tack" proseal on the access plate. When you get the access plate off please do let us know how you did it & if it was a total PITA. If it's not to bad, I may just use normal pro-seal.

Thanks Ryan
 
I am interested to know the outcome of this leaking BNC issue in the OP. Did you replace the BNC? Were you able to do it with the tank on the plane?

My left cap indication has been acting up for a couple months and I have noticed fuel at the BNC. Disconnected, cleaned, reconnected - no improvement. This weekend I am going to make sure it is not a sending unit issue. I would rather replace a unit for $140 than open the tank, but I'm afraid the BNC will need to be replaced.
 
I have not tackled the leaking bnc yet. Plan to do so at annual time...soon. For now it is plugged.
 
BNC connector

Is there any way to identify if it's the "Made in China" connector after it's been assemble to the tank? I purchase a partially completed wing and the tanks are done.
 
Daniel S. said:
Iv'e compile a list of reported leaks & trying to avoid them all :eek:
Click to expand...

Daniel,

I sure would like to see your list, if you don't mind. I'm about to seal up my tanks (i.e. install the baffles), so it's my last chance to double/triple check all the "weak spots." thanks.
 
Mike-
on the 10, you have a bit more area to cover. For me it was a pretty short list... The BIG number uno is dont try to be an artist & skimp on the sealant!!!! I used 2.5 Quarts of PPG Desoto 890B2 ($$$$$). I used a proseal gun to lay down FAT beads on every joint & formed nice fillets with a brass spoon. No popsicle sticks used except for mixing. I also scuffed, layed down PPG PR-148 adhesion promoter, topcoated every cured joint / encapsulation with lab grade toluene thinned sealant... You'd be amazed what you find after you scuff your cured joints & encapsulations with a fine stainless steel brush!!!

http://www.yardstore.com/browse.cfm/4,5955.html

http://www.yardstore.com/browse.cfm/4,6419.html

Anywho-
I'll stop blabbing about my process. Here is the Key point I came up with

#1-Thanks to Walt, plate-nuts were pointed out as a big leak risk. domed /sealed plate-nuts cure that. I top coated those also :eek:.

http://aircraftproducts.wicksaircra...08?&plpver=10&origin=keyword&by=prod&filter=0

#2-The rear baffle. If you search weeping rivets & look at the pictures folks have posted here, you'll quickly notice that most of the complaints about weeping rivet are located on the rear baffle joint. and Vans cautions you about build up here But I loaded it up, especially in the corners, wet riveted in the same session, cleaned up the eternal excess, encapsulated all the rivets, put waxed paped on spar & clecoed in place to cure.

#3 I didnt do this but dimple the skin & rear baffle rather than countersinking. The baffle dimples can be touched up with a debur bit for a better skin-dimple fit. This ensures perfect alignment. If you kind of paint the sealant on this joint with an acid brush AND lay down a bead dead center on the rivet line, plenty squeezes to form a nice consistant bead on the inside while still leaving room for the water drain line.

#4 for the capacitive sender plates, be sure the wire - terminals are sealed to the plate and wire insulation on both sides of the plate to ensure no fuel seeps into the wire & out the BNC connector.

#5 AN fittings use only a small amount of sealant to seal during assembly (not the threads) & then seal well with decent fillets on the inside after torqueing... Also Note that there are different torque values for AN fittings, bulkhead torque values & flared tube torque values. I posted those here a while back

#6 Take your time!!! :D I spent about 130 hours on my tanks. If they leak any time down the road, I'll litteraly cry.
 
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