Possible tank leak search help needed.

[beeryboats]

Hi all,
I posted a help needed on this issue before, but now I have a photo. I got the header tank out without leaking a drop of fuel even though it was half full. The secret you ask? All the inlets and outlets were plugged solid! And I removed the semi-rigid rubber fuel line on the right side. At one time the builder opened the hangar door to find a puddle of fuel and an empty R/H wing tank. Since then it has set for ten years. So now I'm looking for a leaking tank problem. I've been told to do the balloon on the cap vent, but take a look at the photo and tell me if those fittings look ok to you.
Thanks,
Jay

[cap01]

pretty nasty looking but probably didn't leak a tank of gas on the hangar floor .
I'm not a fan of a poly / galvanized combo. if it needs taken apart , Kitfox has some permatex 9a that works really well , a little messy but works well for sealing the fittings in the fiberglass tanks . just be careful not to over tighten and strip out the threads in the fiberglass when you put it back together .

[jrevens]

Hi Jay,
That looks like a nylon barbed hose fitting. Nylon can get relatively brittle over time & is much weaker than any metallic fitting. Even baring that, I don't think it's a good choice for a fuel fitting. I would personally use brass or stainless steel, or even anodized aluminum instead of nylon. I would use the same metal for the threaded bushing. That's just my personal opinion based on standard aircraft practices.

[Wheels]

Yup, replace that plastic/poly stuff. Your fuel system is the lifeblood of ignition. ignition is the lifeblood of compression … lifeblood of spinny thing in front … or sometimes in back, but ultimately lifeblood of thrust, which is usually how we overcome gravity and … have fun and stuff.
I replaced mine by purchasing the new ethanol resistant tanks and replacing the entire fuel system. Probably NOT necessary if the rest of the system is healthy, but mine was not. I had two power failures related to fuel in 250 hours, so I did the whole thing. I'm not a fan of unsanitary fuel or oil delivery systems. Fix it or walk. Flying isn't an option unless you like to gamble.

[beeryboats]

I know, pretty stupid. I'm going to change over to brass. Is that bushing a finger strainer going back into the tank? I also wonder why they don't put inline filters between the tanks and header tank?

[beeryboats]

Ok, to answer my own question, yes there is a finger strainer. Mine however, has a large hole in the end. It was very hard to photograph, but see for yourself. I'm pretty sure that's a generic item. Aircraft Spruce maybe?

[Dave S]

Beeryboats,

Filters in the line between the wing tanks and header tanks??.....at least in my case I experimented with that.....tested it and found the filter could cavitate if air hit the filter..... to get the flow started again it was necessary to pressurize the wing tank ...after my experiment on the ground I ripped the filters out and stayed with the fuel system design specified in the Kitfox manual before taking to the air.

Other's milege may differ depending on specific components (filter or line size); however that was the experience I had.

Sincerely,

Dave S
KF 7 Trigear flying
912ULS Warp drive

[beeryboats]

That's why I post my questions to the group. So many had issues with the older tanks, I was thinking if you had one tank that was going bad you could isolate the bad tank with a filter while the other good tank was free to flow. Versus both good and bad fuel going to the one filter and shutting down the engine.
I had to settle on Gates/Napa brand barricade hose today as the Goodyear brand is not available. The Napa guy was nice enough to print the specs so I could look at them before I pulled the trigger on the purchase.
As I need to place an order with Spruce anyway I got to thinking about all the sump drains that will need to be rebuilt now while all the fuel is out.

[Wheels]

Ok, to muddy the waters, I do have glass visible filters in my line from tank to header. I also have a vent line to each tank. I fly it and can visually see what's happening and have run several dozen tanks of fuel through the system. The extra vent solved a problem with excess fuel being overboarded through the single vent into a single tank and giving me an asymetrical fuel load in flight.

You probably can over filterize (I just made that up) but to leave out essential filters is a no no. Bing carbs don't like dirt. (check the forum)
I have an inline filter at the tank, a gascolator, finger strainers for the big stuff in the tank, and whatever else comes organic to the carbs and fuel pump if anything.
I used the in line filters because of the old sloshing compound that was coming off my tanks. Now I have new tanks and thats not an issue but I like seeing if there is any crud in my fuel before it gets to far down stream.

[beeryboats]

Ok, so I'm not crazy on the filter idea. I don't see any sloshing compound in my tanks from the filler, but I plan on endoscoping the tanks tomorrow. I'm still not understanding your issue with only the one vent though.

[kitfoxnick]

I have glass filters that can be seen thru the turtle deck. These filters come apart to clean, and have a fine mesh filter. I like being able to see if I'm getting any crud out of the tanks. I would not recommend the use of paper filters.

[Micro Mong Bldr]

Only 1 vent has the potential to cause uneven flow, you have to plumb the vent to both tanks if you have only 1. Probably easier to just have 2.
Cheers,
L

[beeryboats]

L,
I don't know how that could happen when both caps have air pressure tubes pointed forward. I noticed that the left tank has what looks like a poor mans fuel gauge. It's a piece of 1/4" clear tubing that goes from the bottom to the top of the tank. But the builder also left large sections of the end of the tank unpainted with fuel level marks in felt pen.

I took a couple videos with my endoscope of the inside of the tanks. I don't know what to think. I see what appears to be large pieces of epoxy that I can move by thumping the underside of the tank. And on the left side I also see what looks like an area of flaking paint. But that could be just epoxy sticking up too. I was looking for fuzzy fibers and didn't see anything like that at all. I think I'm going to go with in-line filters, at least for a while, and see what comes out of the tanks.:eek:

[Wheels]

Ok, John Mcbean, slap me if I use the wrong word again. Vent line or Return line are two distinctly different components to the fuel system.
When you add the rotax recommended return line to your system, you are giving a route for excessive fuel to be "returned" to the tank. The fuel pump is capable of delivering more fuel than you will use during operations and the return line allows the excessive fuel to go back to the tank rather than be pressure pumped into a carburator that doesn't need it and cant burn it all.

As the fuel returns to a single point, EXAMPLE, left tank, the left tank ends up with more fuel than the right tank. (DUH) On a long flight, say 3 or more hours, it is not abnormal to see one tank at 1/4 full and one tank nearly empty. So I simply added a y connection at the return line from the header tank. I put in a return to the left and one to the right tank. Now excessive fuel is symetrically pumped back to my tanks and I don't see the difference in my fuel load during a long flight. I did this to a set of brand new Kitfox supplied ethonol resistant fuel tanks before I installed them. My Mechanic "friend" used all brass fittings.

Fuel Vent/ is the forward angled tubes on top of your wing and yes it allows ram air to lightly enter your fuel tank to keep possitive pressure in your fuel flow while simultaeneously giving your fuel system a breath of air to keep VACUME from occuring in the system. (Put your finger over a straw and suck through the other end, nothing moves. Open the "vent" and you have flow.)
If you turn them backward, you will create a vacume problem and life can become interesting in a short time, or it could end in tragedy. So, to recap, Vent is air, return is fuel. whatdoyathink? I am unsure about the condition of your tanks but it sounds bad, can you send pics?

[beeryboats]

Thanks for the info, but I'm wondering if we have the same set-up. I have the 582 Rotax two stroke, and from what I've been able to see so far I have a feed line to the header tank from each wing and a header tank vent that goes back up to the right tank. I've been able to trace the fuel system up to the firewall so far, but I just got things moved around so I could get the cowling off. From what I saw yesterday I see the fuel line go to the fuel shut-off, which broke when I turned it, then to the gascolator, then to the fuel pump, then two lines go into the mess of stuff around the carbs.
I'm touching anything else until I can get some photos taken. But I see nothing like a return line. I work at a diesel shop and I'm very familiar return fuel systems. I see nothing like that.

[cap01]

you are correct , you don't have the same set up for your fuel system . my model IV book makes no mention of a fuel return in the system . seems that the fuel return is to remedy starting problems associated with a hot engine where the fuel in the lines on the engine is heated causing the engine to flood for the next start

[Wheels]

Yep, Wheels here is flying a model IV with a 912, not a 582. Someone out there has a clue, today, its not me. But, its a pretty logical system, you wont need a NASA resume to figure it all out. Do check your tanks, they sound like they need to be replaced or reworked. would love to follow this thread and see pix.

[cap01]

wheels is correct , if there is stuff lifting in the tanks you are asking for trouble

[beeryboats]

I'm not sure it's lifting. It looks like globs of resin that dripped down and never adhered to the tank bottom. It's hard to tell from the camera image, but the biggest looks about two inches long. Or maybe the size of your pinky finger. I wonder if I could tape a probe to the camera so I could poke and push at things in the tank? I wish I had an idea of what the internal structure of the tanks looked like. I assume there must be a baffle of some sort. I was going to ask the folks at Kitfox about the tanks when I ordered a new header tank, but I guess they are all at Oshkosh. Lucky stiffs!!!
I gotta work.

[kitfoxnick]

In my original mid 1990's 13 gallon tank there are two baffles. My tanks also had large globs of resin all over the place and was from the original layup. Don't confuse this with the kreem separation issues. The Kreem is tan in color, and the resin is more of an amber color. The new tanks from kitfox are of much better construction then the tanks supplied in then mid 90's.

[beeryboats]

Thanks Nick. Was the kreem, or kream, a factory applied coating? From what I can see, it looks like natural epoxy and mat finish. When I get home I'll try and take some still photos and post them.

[Wheels]

My problem was the Kream coming off the tanks in large and small chunks. You could literally peel it off the filler neck area. When we took out the tanks we broke them but there was no damage to the metal spars or anything. Its not fun but the new tanks fit was perfect and well worth the effort.

[wannafly]

I guess I will enter the discussion. After a 6 day fly around our province I must have gotten some of that dreaded ethanol in my tank. The last day I thought I could smell fuel but not signs of any leak, so thought I may have spilt some on me. After getting home the right tank is showing leaks all over the bottom of the tank and floaters inside of tank. I knew the day would come to replace them. These are pre90s tanks. I didnt build it so it is a bit intimadating to cut my wing open to replace them. Any advice, pictures would be great. Possible pitfalls in the process? Should I take all the covering off the wing and start over? What covering should I use? I best give John a call and get things ordered.

[cap01]

there are some pictures of my tank project in my album . mine would have been somewhat more involved than yours if you intend to install the same size tank . I had two 6gallon tanks which wasn't enough gas so I replaced them with the 12 gallon tanks . required removing a rib and relocating braces . also my wings aren't rib stitched but I wish they were . feel free to ask if any questions come up

[beeryboats]

I called John Mcbean tonight to order a couple things, including a new aluminum header tank. I asked about what I was seeing inside my tanks, and it sounded like he wasn't too sure he liked the idea of loose hunks of resin floating around. He also said some tanks were factory Kreamed. Not good. I swear mine have that coating, but it must be very thin. I need to take some still photos so I can post them to the group for viewing and feed back.

[Av8r_Sed]

I have the early 90's fiberglass tanks that were Kreamed. They have never seen Ethanol gas and the Kream appears as a very thin whitish coating on top of the light tan fiberglass. I don't have any delamination of the Kream (yet) and no gobs of resin, though my tanks have only seen a couple of years with fuel. During the annual condition inspection I pull the finger strainers and inspect the tank interior but have found no loose material in them to date.

[Esser]

I guess I will enter the discussion. After a 6 day fly around our province I must have gotten some of that dreaded ethanol in my tank. The last day I thought I could smell fuel but not signs of any leak, so thought I may have spilt some on me. After getting home the right tank is showing leaks all over the bottom of the tank and floaters inside of tank. I knew the day would come to replace them. These are pre90s tanks. I didnt build it so it is a bit intimadating to cut my wing open to replace them. Any advice, pictures would be great. Possible pitfalls in the process? Should I take all the covering off the wing and start over? What covering should I use? I best give John a call and get things ordered.

Sorry to hear!

I haven't replaced the tanks but if I were in your boat and knowing what I know, I would just cut the fabric off the top of the wing over the tanks(If you have poly fibre) and drop in new tanks. I haven't done this before but I have installed the new tanks. If you want a hand let me know and I'll see if I can fly down to Lethbridge in the Cherokee if the timing works out.

[Wheels]

I'm with Esser, I dropped in the new tanks and just cut the fabric tapes over the tank bays. I'ts a job but no way to be happy about sanitary fuel supply until you know the tanks are clean.
I will try and post some pictures today or this evening. I think I have some valuable photos.

[HighWing]

I have the early 90's fiberglass tanks that were Kreamed. They have never seen Ethanol gas and the Kream appears as a very thin whitish coating on top of the light tan fiberglass. I don't have any delamination of the Kream (yet) and no gobs of resin, though my tanks have only seen a couple of years with fuel. During the annual condition inspection I pull the finger strainers and inspect the tank interior but have found no loose material in them to date.

This has been my experience exactly with one difference. I did use ethanol containing fuel in my first Model IV. When I first looked in my tanks - 1993 factory Kreemed - I was disappointed to find that the Kreem was a very thin coating rather than the thick rubbery coating I had expected. It was my expectation that was wrong. I believe the Kreem was initially used to fill pinholes in the fiberglass rather than fill the exposed weave of the glass or protect the resin. I re-Kreemed once in the right tank because of very small leaks on the top of the tank just outboard of the filler neck that somehow caused eighth inch blisters In the Aerothane. After removing the Kreem, I tried filling with fuel and the tank held fuel like a colander would hold water - drips everywhere. After re-Kreeming the right tank - no issues for the rest of the 900 hours of flight time over nine years. This was with mostly autogas with 10% EOH but avgas on long cross countries.

Folks often relate the Kreem coming off in sheets to "mold release" This is not likely as the tanks are made up in female molds and then mated. The mold release would be on the outside - the smooth side. My guess is that the Kreem failures resulted because polyester resin is oxygen inhibited and the resin surface exposed to the air will not cure, but remain tacky due to the oxygen contact. Add Kreem to a layer of uncured resin and eventually the uncured resin will dissolve away leaving the Kreem floating on nothing. (The likely reason the new EOH resistant tanks require chemical rinsing before use is also due to the oxygen inhibited uncured resin on the (inside) surface of the tank - dissolve the uncured surface resin and move it to the carburetor and you will have a mess). Surface Type resin has a wax in the resin that floats to the surface and protects the surface from the oxygen, but I am not comfortable with adding Kreem to a waxed surface either.

I suspect over the years, more than one vendor manufactured the tanks - both my tank sets were manufactured by Denney Aerocraft. And without a doubt, even with a single vendor, different workers made up the tanks. These resins are extremely technique sensitive. A lot of variation can be introduced by resin quality, mix ratios, shop temperatures and simple attention to detail. Remember the old adage, "Don't buy a car assembled on Mondays or Fridays". I am afraid that some of us got tanks "made" on a Monday or Friday. The sad thing, in my opinion, is that the Kreem unfairly took the rap. Put any coating on a poorly prepared surface, whether it be a fuel tank liner or the finish on a flaperon and bad things can happen.

[beeryboats]

Thanks Lowell. Did you get your bleed screw back? When I talked to John he said to stay away from oxygenated fuel (autogas). I never did figure out if it was in relation to the tanks or the hoses.

So how bad a job is it to change the tanks? I'm not so worried about the price as I am about the job itself. How bad does it look when you're done? How did the paint match turn out? And I assume the wings have to come off.

I knew there was a fuel leak issue when I bought the plane, but I hoped it was a bad line. I had no idea the early tanks were crap until I bought the old girl, brought her home, and got on the forums. Yuck! Help!

[beeryboats]

Can those of you that built your Kitfox's back in the '90's tell me if I take the wings off, can I shake the odd bits in the tanks outboard so I can suck them out with the vacuum through the filler neck? I really don't want to remove the wings, and I really, really don't want to replace the tanks. She is so pretty I just can't stand taking a knife to the wing fabric. But I don't see anything amiss besides the chunks of resin. So, can I take the wings off and shake this crap near the filler neck or not? Where are the holes in the baffles?

[Wheels]

Here is a pic of the old tank on top of the new one. note the obvious difference in the material. You can count the new fittings, one of them is the fuel return.
I know you don't want to do it. I don't blame you and it isn't for the faint of heart. I would not tackle it without an A&P mechanic and now you have a bill.

As for taking off the wings, no problem on a model IV. take a look at the items you will disconnect. Pitot, fuel lines, strobes, return lines, hinge pins and voila, a two man job in about 2 hours if you go slow. Do you have disconnects on all your electrical? can you vacuum out the tanks and not remove them? Did yo say you didn't like the visual filters?
can you get more crap out of the wings by shaking them or is a vacuums the safe way? I changed em, I'm happy, I know I have done everything I can do to give a clean fuel supply to my plane.
For what its worth. I believe it was free.

[beeryboats]

Tanks for the photo! I was wondering where the baffles are in the tank so I can see if I can get the chunks out. I assume there is a baffle about where a rib would be in the wing. But where are the holes in the baffle so I can shake the pieces the right direction so I can suck them out through the filler neck.

[kitfoxnick]

I've done the wing tank replacement three times now. It can be done in two to three days. The holes in the baffles are at the front and rear and aren't much more than an inch in diameter. Be careful vacuuming out the tanks you could collapse the tank if you put to much negative pressure on the tank. If using an electric vacuum guard against igniting the fumes being drawn into the vacuum. that could cause an explosion. If your tanks aren't leaking and the Kreem isn't coming off consider putting a glass cleanable filter after the wing tank but before the header. Most of the loose resin I found after cutting into my tanks wouldn't have made it past the finger strainers.

[Wheels]

Nick nailed it. I'm looking for a pic of the tanks I removed. I cut them up and inspected them forensically. they were NOT healthy.
I"ll try and get it to you tonight.

[beeryboats]

Thanks guys. No chance of a boom with these tanks, they've been dry for ten years. I didn't even get a whiff of gas out of them. I doubt I could collapse the tank with the outlet wide open and the neck half open. And I'm sure you're right about the large pieces. I really want to post some still photos so you guys can take a look. I'm sure the Kream, if it's there, is fine. I'm just worried about the massive leak at some point in the past. I guess I'll do the balloon test this weekend if I can find a balloon large enough for the filler neck. My dad used a rubber glove, but I don't usually keep those around. They go rotten too fast.

[wannafly]

Does anybody make a polymer tank. The 13 gallon ones. Are the new "resistant resin" from Kitfox going to stand the test of time? Just asking?

[Av8r3400]

There was a company making polymer tanks that went inside the existing fiberglass tanks. I don't know if they are in business anymore. Kind of a goofy setup, IMO. Cut the top off the tank insert two new tanks with hoses and clamps then put a piece of plywood over the opening. Not for me.

So far no one has complained of a failure of the "new" tanks, that I know of...

[Wheels]

If that tank ever starts leaking, I'll turn my plane into a bon fire and roast marshmallows. I don't think there is a chance of that, but then again, I'm not a chemist.

[beeryboats]

Great New! My suspect R/H tank passed a latex glove test with flying colors. I've attached a photo from each tank. Let me know what you think. I'm inclined to run with what I have. The rod you see at the bottom of the photos is my "pointer" taped to the camera.

Ok, I give up. The kb size of the photos makes them too small to see. They seem to email just fine.

[Av8r_Sed]

The pics you posted for some reason stay postage stamp size for me. I can't make out any detail.

[beeryboats]

The pics you posted for some reason stay postage stamp size for me. I can't make out any detail.

Yeah, I know. For some reason they max out the allowed pixel size of the website. I would love a second opinion if you're willing to PM me your email. They seem to email fine.
Jay