Best way to fix tank leaks

Despite having "finished" my tanks around two months ago, I am just getting around to truly leak checking them. Early results seem to be that the only leaks I can detect with Snoop are:

- Small leak around the fuel sender plate where it makes a seal with the rib (screws are not leaking)

- Bulkhead Union seems to have a leak, or the hose clamp is just not tight enough, it is frankly hard to tell which it is right now.

Question is: To fix a leak in either of these places, especially the sender plate, is it necessary to remove the actual plate and start again or is it sufficient to lather additional proseal on the outside of the seal and just fill the gap? I am anticipating the answer to be that you need to redo the whole thing but want to get advice before I go there.

Thanks.

Like others, once I adjusted the tightness of the fuel cap there was no need for me to put packing tape across it anymore. Initially it seemed like I would need to put the usual layers of tape but tightening worked. Thanks for that tip.

I have heard of one way, but never tried it, that sounds like it might work. If I have any trouble with the leak check on my tanks I will consider trying this before I do any major surgury.

This comes from an old airplane mechanic that used to work on prop airliners back in the day...

Empty your tank and set up a system to puts a slight vacuum on the inside, nothing more than a pound or two PSI. You don't want to collapse your tank and destroy it.

Take some pro-seal and mix it normally. Then take a dab of said pro-seal and thin it out to a very liquid form with lacquer thinner.

With the tank under vacuum, liberally apply the liquid pro-seal/lacquer thinner mixture to the leak area to pull the mixture into the leak path.

Remove vacuum and allow for normal pro-seal cure time and then re-test.

If you decide to try it, let us know how it worked out.

Howdy, I'm working on sealing my tanks, under another thread in the general maint thread.
http://www.vansairforce.com/community/showthread.php?t=126019
I wasn't sure what to use for leak checking and had heard that sometimes using the soap/water/squirt bottle you may introduce your own bubbles so my brother recommended:
http://www.amazon.com/gp/product/B000EDUTMC?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s02
Which I ordered. But then I see that someone asked for the MSDS to see what exactly was in it as they didn't want it eating rubber seals etc. Anyone have any experience with this "Camco 10324 Gas Leak Detector with Sprayer - 8 oz"? Certainly don't want to cause any damage. ie: if it melts proseal, that would be a mess!
I realize it is meant for checking propane gas lines, so I'm not sure if they specially formulate it for interacting with the propane or something like that. Maybe the safer bet is SOAP/WATER! I'll email them and ask for the MSDS.

Mark

I am using Snoop and have had great luck with it so far.

Just adding even a small amount of air pressure to the tank allows the bubbles to show if you have issues.

Not sure if I will try that suction idea to fix the leak as it is in a very accessable area. Would love to hear opinions if I can just add proseal on top of the outside of the plate or if I need to redo the plate for the sender. I bet just putting some on would work.

Boomer506 said:

I have heard of one way, but never tried it, that sounds like it might work. If I have any trouble with the leak check on my tanks I will consider trying this before I do any major surgury.

This comes from an old airplane mechanic that used to work on prop airliners back in the day...

Empty your tank and set up a system to puts a slight vacuum on the inside, nothing more than a pound or two PSI. You don't want to collapse your tank and destroy it.

Take some pro-seal and mix it normally. Then take a dab of said pro-seal and thin it out to a very liquid form with lacquer thinner.

With the tank under vacuum, liberally apply the liquid pro-seal/lacquer thinner mixture to the leak area to pull the mixture into the leak path.

Remove vacuum and allow for normal pro-seal cure time and then re-test.

If you decide to try it, let us know how it worked out.

Click to expand...

I have fixed leaks on heavy aircraft using a similar method but you definitely do not want to pull any vacuum on the internal volume of a tank! The method to use is to apply plastic sheet and sealing putty adjacent to the leak point on the outside of the tank. Then you can apply vacuum and draw the sealant though the leak path from the inside of the tank. Also be careful of what chemicals you use to thin the sealant. I have had limited success with thinning sealant with solvents over the years, some times it will cure, and other times it never cures. It may be better to but a pint of A sealant if you want to try this repair method.

To the OP: if the leaks are small I would try applying an additional overcoat fillet on the outside and let it cure for a few days before I tried anything else.

Perhaps this will give an idea of how to fillet or cover things.



A mil, incidentally, is .001 inches, so 250 of them are a quarter inch; 60 are .060 inches.

This will show how I dabbed it over the rivets:



In the photo, I hadn't yet covered the edges of the flanges - I did that before closing the tanks.

I like to use the type A sealant, which has a honey-like consistency, for this. I bought some plastic hobby syringes and used them as applicators. Worked great! In some places I used a narrow Popsicle stick to shape the bead.

It's completely compatible with the thicker and more common type B sealant which Van's sells, which I used in between the parts.

I leave the sealant in the syringe and when it's cured, it comes out. In most cases I can reuse the syringe at least once.

Dave

sealant thinner

This from an A&P/IA who seals tanks on larger turbo-prop/recip engines:
Thin pro-seal with MEK as it wicks off & is usually the thinner used in the manufacture process. a consistency of mayonaise is best. Just my $.02 Nice job BTW on your tanks..

Flamemaster thins CS3204 Class B with toluene, per their tech rep. It is less than 3% by weight in the white component, per the MSDS.

Class A is thinned in production with toluene and/or MEK. The MSDS lists <12% and <15% respectively.

For thinning in the field, I would choose based on my desired evaporation rate, using MEK only if it was cold in the shop. My reason would be the difference in vapor pressure, MEK being 4x to 5x higher. There are quite enough voids in shop mixed sealant without blowing more.

Jerry Fischer said:

This from an A&P/IA who seals tanks on larger turbo-prop/recip engines:
Thin pro-seal with MEK as it wicks off & is usually the thinner used in the manufacture process. a consistency of mayonaise is best. Just my $.02 Nice job BTW on your tanks..

Click to expand...

I agree that MEK is the solvent to use IF you decide you HAVE TO thin sealant. I have used this method in the past when A sealant was not available, and it works MOST of the time. I say this becuase ther have been days where I have spent the entire day in a tank scaping out some B2 sealant that was thinned with MEK that did not cure properly. Other things to consider are adhesion characteristics and strength of the thinned sealant.

Got a message from CAMCO, they state THEY WOULD NOT USE THEIR PRODUCT IN THE APPLICATION THAT I DESCRIBED.
Guess I'll give it to my brother!

mantry said:

Got a message from CAMCO, they state THEY WOULD NOT USE THEIR PRODUCT IN THE APPLICATION THAT I DESCRIBED.
Guess I'll give it to my brother!

Click to expand...

We have that stuff where I work as well as Snoop. I have used both and they both work great. They WILL NOT cause any damage. Lots of companies get nervous when you tell them you are using thier products for aircraft maintenance purposes.

FYI: water mixed with a fairly high concentration of liquid dish soap works well. You will need to use you're fingers and "spread" the solution around a bit over the seams to eliminate the large bubbles, then wait and watch the small bubbles to see if they become larger and burst. We are making a huge science project out of something really simple . When you give it a try you will figure it out very quickly

Thanks Mike, yeah I kind of wondered that same thing. The word "Airplane" put them in a dizzy. Should have said airboat...

mantry said:

Thanks Mike, yeah I kind of wondered that same thing. The word "Airplane" put them in a dizzy. Should have said airboat...

Click to expand...

Legend has it that Chuck Slusarczyk's CGS Aviation often became "Chuck's Garden Supplies" when buying 6061 aluminum "irrigation tubing" by phone.

Looking through the paperwork on a bipe I own you can see where the builder's invoices started showing him as a toy manufacturer...

Snoop is not only awesome but it is cheap too. Find a local air systems supply company. They usually sell swagelok fittings when u are looking for them. Snoop comes in an 8 oz bottle with a handy long tube to apply it for about 4 dollars a bottle. I bought two but only used partof one.