Fuel tank line seep leak

[SkySteve]

I have one fuel tank line that seeps a little fuel at the point where the fuel tank line (copper/brass?) attaches to the plastic header tank fuel line. I've tried multiple clamping techniques but in time the seep always wins. Question: Should I try (1) swaging the fuel tank line to expand it; (2) add a ferrul to the fuel tank line with clamps on both sides; or (3) some other technique that somebody smart about these things already knows will work?

[Dave S]

Hi Steve,

I am a little unclear about the details....is this leak at the fuel tank end or at the header tank end of the hose? Got a photo?

FYI - connections on both ends of the hose should go over barb fittings which seal up pretty good and hold with light clamp pressure.

If a straight hose/tube go together, it can be difficult to make these behave.

What kind of clamp are you using? the conventional screw clamps, particularily the small ones, can leave an uneven pressure on the hose, an auto fuel injection clamp with a smooth contact surface all the way around can help sometimes.

Might check on the condition of the inside of the hose.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp
St Paul MN

[SkySteve]

Dave,
No photos right now. I can get one on Monday. The location is at the wing fuel tank end. My fuel tank has a smooth copper (I think) 6" long line coming out of it. The clear plastic fuel line is clamped over that with a regular screw type clamp. This flue line then runs downward to the header tank. The problem area is where the plastic line goes over the smooth copper line coming out of the wing fuel tank.

[Dave S]

Steve,

OK, That makes sense now. I think the construction of using a smooth copper tube slipped inside the hose with a screw clamp might be the source of problem....this is a non-standard construction for a fuel line connection.

Don't know what your fitting going into the wing tank looks like, but, I believe most had a finger strainer screwed into the wing tank with a right angle fitting screwed into the finger strainer and the right angle terminating in a barb fitting.

I have attached a photo which shows the fittings I am talking about. BTW - the access panel on the bottom of the wing at the fitting is non-standard - I just wanted to be able to get at the fitting if I needed to.

There are tools to put those little bumps on a metal line like you have on a fuel hose fitting on a car, but I think they are pretty expensive. That might work if you can get your hands on one cheaply. A compression fitting ring would probably just leak between the ring and the copper tubing...they will seal up only with using the complete compression fitting.

I think you have several ways to go, but I think the straight slip joint will continue to do what it is already doing.

Good luck, let us know how it gets solved.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp
St Paul, MN

[n85ae]

Sounds like my header tank (and many others) I fight battles with fuel smell
constantly, I have pretty much concluded that the header is simply porous
enough that fuel migrates right through it. I don't get stains (I run 100LL)
I don't get drips, but I always have odor. Year after year I go through
it at annual and occasionally find a weepy fitting (you guessed it) at the
header which I fix (again). I think the only real solution is to scrap the
plastic header and go to the aluminum one.

Regards,
Jeff Hays
Series 5, IO-240B


I have one fuel tank line that seeps a little fuel at the point where the fuel tank line (copper/brass?) attaches to the plastic header tank fuel line. I've tried multiple clamping techniques but in time the seep always wins. Question: Should I try (1) swaging the fuel tank line to expand it; (2) add a ferrul to the fuel tank line with clamps on both sides; or (3) some other technique that somebody smart about these things already knows will work?

[SkySteve]

Dave, I like yours and it's probably a result of those like Jeff and I have. Jeff, my problem is not at the header tank. It is at the exit of the wing tank. I'll go to the Aviation Department at Home Depot and see if they have some assorent of fittings that might work. If there are any additional ideas out there I would love to hear them. Thanks so much for your responses.

[Dave S]

Jeff,

When I got my kit it was before John Mcbean had the company.....it came with a plastic tank that turned out to be defective.....didn't leak but it smelled up the cockpit.....a little investigation revealed a number of bubbles in the plastic which resulted in spots where there was only a couple thousands of an inch of plastic separating the cockpit from the fuel.

I got one of the first aluminum tanks that John made up after he got the company and I couldn't be happier with it....no stink....no leaks...the only way to fly in my opinion.

I think some people have had good luck with the plastic tanks but I did not and never liked the idea.

Another way fuel odor can get in the cockpit is through the fuel hose if a person has the old style auto fuel hose. The new fuel injection hose is great but the other will permeate gas fumes.

Take care,

Dave S
KF7 Trigear
912ULS Warp
St Paul, MN

[HighWing]

Steve,
I think the easiest way to fix your problem without redesigning the whole system is to pick up one of the compression fitting rings at HD and sweat solder it near the end of your copper tube. This will create a bead that will expand the plastic line a bit and help prevent the leak. Or you might try one of the small spring clamps (vent line fitting in pic 3). If you might want to try one of those and can't find them locally, send a PM with an address and I will send you one - I bought some online. Tell me the ID of the tubing.

On my first Model IV, I had an aluminum header tank and it worked fine, though it was mounted behind the baggage because that is what they did then. This time, I am using the poly tank and am in the process of solving the common problem as a matter of accepting a challenge. A couple of pics will show what the progression has been.

The first image shows what has been the tank for the past four months with no leaking. It consists of the typical brass bushing, but machined to accept an O-ring near the neck. The problem with this is only a perceived one as the machining left very little metal between the bottom of the O-ring seat and the inner diameter of the fitting. I was nervous about the possibility of the whole thing just popping off some day.

The second image shows what the solution was. I was able to find 5/16" barb fittings with 1/8" pipe threads. This gave a lot of material between the O-ring seat and internal diameter of the new bushing. I also made some small aluminum collars that would help secure the O-ring as they have a tendency to squeeze out of the minimlal seat on the original.

The third image shows the new units in place with the vent line still showing the O-ring in a simple machined slot on the original fitting.

Fuel smell. I removed the seat pan because I was still getting a bit of fuel smell after the first fix and wanted th check out. There was absolutely no leaking at the fittings - the dry tissue test. And as Dave suggested, the odor comes from the fuel line itself. I don't know how motivated I am to change out those lines.
Lowell

[SkySteve]

Lowell,
I think you are right about sweat soldering a compression ring on the wing tank fuel exit copper line, HOWEVER, I'm afraid if I introduced a MAPP torch to that area I would probably hear my very last CaBoom while I blew myself up. Do you think I can get enough heat out of a solder gun to sweat seal the compression ring to the copper fuel line? And do you think there will not be enough heat to create a safety hazard?

[HighWing]

Unless you can fairly easily remove that length of copper, I think, like you, that heat near the fuel tank would not be a real good idea.

I might suggest another idea. The Lancair I helped with has a wet wing. The carbon fiber skins were vacuum bagged on the molds to the extent you could blow air through them, or at least when you bonded them together with Hysol, you would see that the glue would penetrate through the skins and form beads of the Hysol on the outer surface over ribs, etc.

The solution fuel wise was to paint all internal, except bonding, surfaces with a fuel tank sealant. This was done before closing the wing. That meant that after closing the top and bottom skins, there would be a bead of expressed Hysol at the joint on inner and outer surfaces of the joint. The inner bead, constantly bathed in fuel.

I think I would be comfortable bonding the compression fitting ring with Hysol. Bond the ring and clean the excess. I suspect that the minimal amount left between ring and tube, even if it slowly dissolved would not harm the carburetor or engine and if it ever did dissolve, it would most likely only result in the slow leak you are currently seeing.
Lowell

[SkySteve]

I think I may have just had a brainstorm. What about bonding the comprression ring to the fuel tube with JB Weld? When cured, it is fuel proof!

[Lion8]

Hi Steve. I'd like to offer a few ideas. I don't use the standard slotted hose clamps. I use the smooth hose clamps from McMaster-Carr co. You can get stainless or Galv.steel. Another thing I use is 'Barricade' fuel hose from N.A.P.A. It has many layers within the hose, one of which is a vapor barrier and will not let vapors through the line. I use an aluminum header tank with aluminum fuel line from it to the firewall using AN fittings. There is electrical tape that 'welds' itself together that I always carry. I blew a radiator hose in my car many years ago. I wrapped it with this tape and filled the radiator. It got me home until the next day when I could change the hose. The 'barbed' fuel fittings are a good point as detailed above. Hope this helps, Tom, (Lion8)

[SkySteve]

Tom,
Thanks for your input. I have changed the fuel lines to E-proof lines. I will also be changing the ring clamps to the fuel type several have mentioned here. If the JB Weld idea works, I am thinking the clamp should be placed around the compression ring.

[jwlt500]

One more idea if there is room. Add a compression nut, do a double flare on the copper go from flare to barb, no torch needed.

[jtpitkin06]

Pro Seal Type sealant from ACS
It is fuel proof and stays flexible.
http://www.aircraftspruce.com/catalog/appages/prosealant.php

It's about 20 bucks for 2 oz.

Or if you want the real thing, Same as used to seal Mooney and Cardinal wet wings. FAA PMA approved.

http://www.aircraftspruce.com/catalog/appages/ps890.php

It's about 85 bucks a pint.

JP

[dholly]

The 'barbed' fuel fittings are a good point as detailed above. Hope this helps, Tom, (Lion8)
Hi Tom - I redid the fuel system on my 4-1200 in Sept., 2011 and changed out all the barbed fittings in favor of beaded fittings at that time. Less damaging to hose and far less likely to have a little piece of cut hose crud end up in the circuit somewhere IMHO. Combined with your suggested band (vs. worm gear) hose clamps, should give one the best of both worlds. I remember they were a -very- tough find, so I dug up the source info to share if anyone is looking:

Item#PCO 168-05-04, (10) @ $0.999 EA = $9.99 (on the invoice it looks like S&H was inc'd)

Winco Fluid Power Inc.
PO Box 355
Jamison, PA 18929
Tel: 215-657-4940 (Glenna)
Fax: 215-657-7226
www.wincofp.com (http://www.wincofp.com)

[Lion8]

Hi Doug. The fuel hose clamps are in the McMaster-Carr catalog. That is a great company to deal with. They have good products and delivery is very fast. Of course, here in Southern New Jersey, their outlet is not far from me. Incidentally, it has been a long time but as soon as I get my propeller, I'll be ready for main engine start of the 'Jabiru 2200'. Remember that one?-Tom.

[dholly]

Sorry Tom, guess I was less than clear. The barbed fittings were tough to find.

Re: the Jab start, you got the honors but I expect the video! :)