Need help with a fuel tank leak.

[AX-O]

Well, I guess half of my prayers were answered. One tank out of two is leaking I let the proseal on my tanks cure for about 2 weeks prior to pressure testing them. I pressurized the tanks for about 24 hrs. One of the tanks was good to go (99.99% sure). The other one, not so much. The water level dropped about 2.5 inches over 24 hours. After applying soapy water to every inch of the tank I found a very small leak The leak is coming from the BNC connector. Not from the outside of the connector but from the inside. To be more specific the leak is coming from the small hole in the middle of the connector. I did the same thing on both tanks and applied proseal to the wire and the BNC connector after crimping and soldering the wire. Should I take the access plate off and apply more proseal to the connector prior to resealing the tank or should I replace the BNC connector all together and reinstall the assembly?

 

[bullojm1]

Axel-

Sorry to hear about your leak! At least it is easily fixable! Could be much more buried in these tanks. I don't think you need to replace the BNC connector, just be sure to cover it liberally. Here is a pic of mine:

Good Luck!

 

[brenegan]

wick in some green loctite

 

[vmirv8bldr]

I had the EXACT same thing happen!!!!

Same thing happened to me, I thought it was really wierd. I mixed up some Proseal and globbed it on the back of the connector, then smeared it all around it. Let it cure for about a day then tested again...no leak.

 

[N941WR]

Same thing happened to me, I thought it was really wierd. I mixed up some Proseal and globbed it on the back of the connector, then smeared it all around it. Let it cure for about a day then tested again...no leak.

Ditto for me. This is a common leak area. You really need to cover that thing up with a LOT of pro seal.

 

[AX-O]

Well guys, it did not work I pulled the access plate off and applied A LOT of proseal to the back of the BNC connector. I found a spot that looked suspect and covered it up along with the rest of the connector and wire. Then I let the proseal cure for 10 days prior to testing it. The leak is still there and is leaking at the same rate (kind of like I did nothing to it).

Is it possible for the electrical wire to have a hole on the outer cover and the air is entering it and escaping trough the BNC connector? Seems stupid however, I've covered the BNC connector very well twice now and no joy. I did the same thing to the other tank and it did not leak

Any more ideas???? I want to put these tanks behind me.

 

[Mike S]

and applied proseal to the wire and the BNC connector after crimping and soldering the wire.

Wires have two ends.

What did you do to the other end??

 

[ten4teg]

Fuel Tank Pressure Testing

What is a good way to pressure test the fuel tanks?? I saw on this post that you pressurized them and the water level dropped. How does that work. Did you fill the tanks with water and then pressure test it? Also, what are good connectors to do a pressure test with? Thanks, Tom

 

[AX-O]

What is a good way to pressure test the fuel tanks?? I saw on this post that you pressurized them and the water level dropped. How does that work. Did you fill the tanks with water and then pressure test it? Also, what are good connectors to do a pressure test with? Thanks, Tom

I used the kit from Vans plus a few other AN fitting caps. The kit provides a valve (kind of like on a bicycle tube) that screws onto the fuel drain attach point. You use that to pump air into the tank. The part number from Vans is indicated below.

Fuel Tank Test Kit
Part Number = FUEL TANK TEST KIT
Price = $5.00

Two ways to do it:
1. Place a balloon on the fuel vent AN fitting. Inflate the balloon by pressurizing the tank. If the pressure inside the tank is above approximately 1 PSI, the balloon should pop and prevent damage to your tank.

2. The other way is by using a manometer. Connect a clear hose to the fuel vent AN fitting, fill the hose with water, then pressurize the tank so the water level on the open side of the tube is approximately 2 feet and 3 inches higher than the side attached to the tank. That will ensure approx 1 PSI inside the tank. You will see variation on the water level due to Pressure and Temperature. The ideal gas law (pV=nRT) explains the relationship. Pressure is directly related to Temperature. Temp goes down and so does Pressure.

Hope that helps. If you need to see pictures and what I did, check my log page. http://www.mykitlog.com/users/display_log.php?user=alvarez&project=163&category=0&log=47689&row=3

 

[AX-O]

Wires have two ends.

What did you do to the other end??

The other side of the wire is attached to the fuel sender plates. The wire was soldered and crimped to a connector. Proseal was then applied to the wire, the connector, the bolt and fuel sender plate.

 

[brenegan]

So lemme picture this... in the center of the connector on the
outside of the tank you have some bubbling?

And you opened the tank back up and gooped more proseal on the
connector and wire. IMHO, won't help. Wick some green loctite.
You didn't say if you tried it... I'll bet you didn't.

 

[AX-O]

So lemme picture this... in the center of the connector on the outside of the tank you have some bubbling?

Yes, that is correct.

And you opened the tank back up and gooped more proseal on the
connector and wire. IMHO, won't help. Wick some green loctite.
You didn't say if you tried it... I'll bet you didn't.

I opened the tank and apllied proseal to the connector and wire. I did not try the green loctite. Where do I find it and how durable would that method be? Will it still be good 5 years from now? Thanks for the help.

 

[brenegan]

I can't tell you about 'five years from now' sorry.... My tanks aren't flying yet. What I can say is this, the stuff wicked in very well, didn't affect
electrical conductivity and resolved my problem. That's what I can attest to.
I pressure tested this tank for several days on accident because I went on
a business trip at the time. Search for 'green loctite' on this site and you'll
see it's used to resolve issues in other cases of tank leaks and is very
durable. Google for green loctite for places to buy it. Make sure you get the 'loctite' brand.

 

[RV8RIVETER]

VACUUM

I am sorry I saw this thread late. I had the same problem. I reopened and then packed the proseal as hard as I could and then taped a shop vac to the outside of the connector and pulled a vacuum on it for about 45min to an hour. Had no more leaks. If I were to do it again I would spend the $ and buy an aircraft grade, tank bulkhead BNC.

 

[brenegan]

I am sorry I saw this thread late. I had the same problem. I reopened and then packed the proseal as hard as I could and then taped a shop vac to the outside of the connector and pulled a vacuum on it for about 45min to an hour. Had no more leaks. If I were to do it again I would spend the $ and buy an aircraft grade, tank bulkhead BNC.

I bought some of those 'Aircraft grade' bnc connectors at boeing surplus
before the retail store closed; never used them. strictly speaking, you don't
need them; but they would probably eliminate the leak if installed correctly.
Then again, the kit supplied connectors won't leak either imo.

 

[AX-O]

Well, the tank leak is fixed (99% sure)

I did not want to use the loctite method because I did not know how permanent that fix would be and I would not want to deal with it after I was flying. I decided to try something else. I mixed a batch of proseal and poured MEK in the container to thin out the proseal. After I was happy with the proseal (consistency like runny toothpaste), I used a toothpick and placed proseal on the small hole in question. Instead of putting a vacuum on the tank, I decided to connect the line that I was using as the manometer on the outside of the BNC connector and blew the proseal inwards by using my mouth. I repeated that step 3 times until no more proseal would go in. I placed proseal one more time on the middle hole of the BNC connector and then used about 20 psi to blow the proseal inside the connector (tank was free to vent in case I blew out the BNC connector). Once that was done I cleaned the excess proseal from the connector and waited almost 2 weeks prior to testing. The tank was tested for about 16 hrs and the water level actually went up. One more major step accomplished.

 

[Lucio I-NLCM]

how is your BNC leaking?

hello gent

After 6 years and 630h I found the same fuel leaking problem, my left wing leak fuel from bnc connector.

so after years from your leak fixed, I’m wondering if it still doesn’t leak or…

I’m doing the same way in first, hoping to fix it without pull access plate.

thanks a lot

Well, the tank leak is fixed (99% sure)
I did not want to use the loctite method because I did not know how permanent that fix would be and I would not want to deal with it after I was flying. I decided to try something else. I mixed a batch of proseal and poured MEK in the container to thin out the proseal. After I was happy with the proseal (consistency like runny toothpaste), I used a toothpick and placed proseal on the small hole in question. Instead of putting a vacuum on the tank, I decided to connect the line that I was using as the manometer on the outside of the BNC connector and blew the proseal inwards by using my mouth. I repeated that step 3 times until no more proseal would go in. I placed proseal one more time on the middle hole of the BNC connector and then used about 20 psi to blow the proseal inside the connector (tank was free to vent in case I blew out the BNC connector). Once that was done I cleaned the excess proseal from the connector and waited almost 2 weeks prior to testing. The tank was tested for about 16 hrs and the water level actually went up. One more major step accomplished.

 

[Lucio I-NLCM]

hi
I did exactly the same like AX-O and fix the problem; no more any leak from bnc connector.
Just to know, I used tank sealant expired from 2009 it work perfectly
Yes guys, I’ve checked before use it

thanks AX-O