Failing gas tank sealant
 

Question: How effective are pencil-style fuel screens when your gas tank sealant is failing and shedding flakes? (see attachment of screen)

Situation: My gas tank was boiled and sealed less than ten years ago. This was a competent job by a well-known local shop. But, ethanol has done its work, causing the sealant to shed in large chunks. I tried to rinse it out with clean gas, but 1/4" flakes are still coming out.

This is my first time using such a fuel screen.

Will the fuel screen clog up? Will I need another gas tank boil, or will the screen stay relatively clear and functional for years to come?

Re: Failing gas tank sealant
 

It depends on how much is flaking off the tank. That screen is about 2 inches tall so if an inch and a half is covered it would still probably flow enough fuel to keep you going. You can see the screen by looking down in the tank so you can keep an eye on it.

Re: Failing gas tank sealant
 

You may be surprised at the size of flakes that you can't see...
-Tim

Re: Failing gas tank sealant
 

Try to fish as much of the old sealant as you can, then install a pencil filter and give it a try.


The old sealant was fine until the ethanol came along.


Chris W.

Re: Failing gas tank sealant
 

I’ve been going thru the same thing. Mine had been working for 20yrs, then came corn gas.
Mine was coming off in big sheets in the beginning. It was covering the gas outlet in the bottom of the tank and shutting the motor off.
I kept pulling the larger sheets out with a coat hanger. They didn’t have the “pencil filter”
When this first started happening. So I happened to have my airless sprayer apart cleaning it and there was a real slick filter in there much like the pencil filters except it screwed in to
The spray wand. I tapped my shut off valve and screwed it in and it has worked great.
It is also a little taller than the pencil filter and made out of stainless steel.

Re: Failing gas tank sealant
 

I think I would forget the pencil filter and build what's called a dirty leg. Do a search on this site to see how it is made and run with it until the flanking stops.

Re: Failing gas tank sealant
 

I bought a 56 Farmall that had never seen the inside of a shed...the tank was terrible. I pulled the tank and pressure washed it until clean water came out, drained it and left it in the sun a week (100F) until it dried. I installed a pencil filter and havent had a bit of trouble in 3 years.

Re: Failing gas tank sealant
 

why I only use the Hirsch sealer. the white stuff. guaranteed to not flake off and used in airplanes.


the others all come undone.

Re: Failing gas tank sealant
 

I’ve seen all of them fail to some degree
What is the guarantee? Send you another quart?
The problem is the ethanol gas....mostly
Run 100% gas

Re: Failing gas tank sealant
 

I used the Hirsch sealer, so far so good. If I had to do it again, I would just send my tank out to B. Terry Restorations.

Re: Failing gas tank sealant
 

Wow, I appreciate that referral however I need to make this public and this is probably the best place to start.

Yesterday we shipped 6 restored tanks back to their owners, -and we probably have that many left to do and once those are completed then I am going to quit offering this service. The reason is a simple but very stressful one for me. This service has grown to where it has become overwhelming for us in that we are already overbooked in the shop with other restoration work, and the amount of tanks that people want to send just keeps growing.

In the perfect world, I would like to find someone already in the Model-A hobby that we can just pass the torch on to them and let them start doing this as a cottage industry to possibly help subsidize their hobby -or maybe a sideline business. I would like to pass on the info I/we have learned in restoring these, and assist whomever in learning this where they can help others out there. I probably won't sell any of our fixtures and equipment as we will still restore tanks for vehicles we are restoring, but if someone else is interested in taking this on, please send me a PM.

Re: Failing gas tank sealant
 

I’ve seen all of them fail to some degree


I sure hope not. wouldnt want to be up in a plane and have it fail.

Re: Failing gas tank sealant
 

Here are some pictures of the so called dirty leg, the sediment trap on the right is the one I made, I used 1/4 inch valves, the other picture I believe has larger valves which would allow for passing larger flakes along with a longer down pipe, all parts from hardware stores, leave the pencil filter off. I do not know who to credit for the first picture

Re: Failing gas tank sealant
 

In aircraft, we use a different sealer. It's not white like latex. It's either gray or brown depending on the brand. A lot of aircraft have wet wings so the rivets also have to be sealed at installation or anytime they start to leak. 100LL Avgas doesn't have any alcohol in it. It's about the best quality gasoline type fuel refined & blended in this day and age.

Re: Failing gas tank sealant
 

Probably should correct/amend....
I probably have NOT seen ALL of the sealers!
But the 4-5 used in the somewhat recent past seem to have had issues down the road
Not an indictment of ALL that would be unfair! The real problems could be caused by poor prep rather than product; or a combination tjereif. The only sure way is to open them up as Brent has described in the past
My “mis-speak”!!

Re: Failing gas tank sealant
 

Hello ,many of the General Motors cars of this period have filters similar to the pencil ones you have mentioned they seem to work good for the last 60 plus years.

Re: Failing gas tank sealant
 

the white stuff from Hirsch is not like Latex........


get it on your hands and try and scrub it off.

Re: Failing gas tank sealant
 

I agree with you on scrubbing it off with soap & water, ...but rub your hands together with some thinner, acetone, or gasoline on them and watch what happens. :eek:

Re: Failing gas tank sealant
 

I just mentioned that it has the appearance of latex rubber. I didn't state that it was.

Re: Failing gas tank sealant
 

Brent, I sent you a pm. Not trying to harass you, just want to make sure you did receive it.

Re: Failing gas tank sealant
 

I don't guess i received it. Send it again.

Re: Failing gas tank sealant
 

Hi Brent
I sent you a PM also. I haven't heard back. Sounds like you are not receiving your PM's.
Dave

Re: Failing gas tank sealant
 

I have heard that planes can NOT use corn crap gas because it is known how it can mess things up.


Be a shame to see a plane fall out of the sky and hit an ethanol plant. LOL

Re: Failing gas tank sealant
 

The few I know that fly Cubs use regular grade pure gas

Re: Failing gas tank sealant
 

Does the gas tank sealer by POR 15 doe this too?

Re: Failing gas tank sealant
 

There are various reasons why airplanes cannot use ethanol adulterated fuel.
The ethanol dissolves the resin in some composite fuel tanks. Fuel systems are not sealed like modern automotive fuel systems so the ethanol absorbs moisture from the air. Once the ethanol is saturated with water corrosion starts. That’s the same reason boaters don’t use it. Experimental (amateur built) Airplanes with aluminum fuel tanks and Rotax engines use it regularly. Certified aircraft are not allowed to use it by Federal Aviation Rules. Many lower horsepower certified airplanes can by regulation use non-adulterated auto fuel. Adulterated fuel is more prone to form carburetor ice on cool days with high humidity.

I hate working on airplanes that use any form of auto fuel, it stinks and you can’t wash off the stink. Avgas does not stink and the sweet smell disappears in a few minutes.

Re: Failing gas tank sealant
 

Aviation matters are regulated by a different part of the DOT than automobiles. The FAA wasn't always part of the DOT but it became part of it in 1967 when the DOT was formed. The Federal Aviation Administration sets the safety standards for the aerospace industry throughout the whole range of operation. Its goal has always been to make the industry more safe. Aviation fuel is just a small part of what they regulate and is exempted from all other laws regarding motor fuels in the US. There are diesel engines certified now but they run on Jet A turbine fuel.

Some STCs (supplemental type certificates) were developed to run older aircraft engines on Mogas but they require testing of it before use. The Mogas also has to meet specification for vapor pressure. This was an effort to drop the octane rating for fuel back to nearer the older 80/87 level for older lower compression engines. After some problems with this practice Lycoming issued a service instruction (latest revision SI-1070AA. Folks can look at this document on line from Lycoming engines and it gives a person an idea of how careful they should be when running Mogas. Even the STC documents give folks an idea about testing for ethanol in the fuel and how to find the good stuff. Ethanol is not recommended unless it is in at least 91 octane Mogas and no more than 1% by volume. Folks have to be careful about vapor pressure too. It's critical at altitude and vapor lock up there would be no fun. Winter Mogas fuel blend is the one to worry about most. They set the volatility way up for winter fuel and it's not controlled all that well. After all this, the STC documents still recommend running a tank full of 100LL every 75-hours just to lube the valves a bit or Avgas can be blended with Mogas. It' seems to be getting harder for folks to get fuel to meet the STC specs these days but it's still out there if you know where to look.

https://www.autofuelstc.com/

Re: Failing gas tank sealant
 

Brent, I did send another private message as this is something I may be interested in doing. Looks like it is a service that is needed and I love these old cars. ;)


I would not fly knowingly in anything that has had corn gas in the tank. I was seriously looking at experimentals that I could base on my property, "Just Aircraft, Super STOL", check it out on YouTube. You can almost land one in your driveway. This is at the factory along the North Carolina, South Carolina border. https://youtu.be/TZwuQBJyWe0

Re: Failing gas tank sealant
 

So are you suggesting that you've experienced or seen problems with the Hirsch brand sealer?

Anyone else ever had problems with the Hirsch brand?

Re: Failing gas tank sealant
 

Different gas in aircraft, no alcohol in it that I know of. I wish I had a dollar for every gal of 115/145 Avaition gas I have pumped.

Re: Failing gas tank sealant
 

We've had the sealant fail in two Model A gas tanks since ethanol was added to gasolene. Both tanks were cleaned and processed by Moyer's Tank Farm near Pittsburgh, PA. Due to the baffles and design of the Model A tank, Moyer makes sure that all interior surfaces are clean. Then, they apply the RENU process coating which is baked.

Both gas tanks are working perfectly. Moyer's has a web site and does lots of gas tanks. Again, this is my experience. I'm not in any way trying to detract from other products or services.

My guess is that many of the poorly running Model A's are due to rust, corrosion, etc. that get into the carburetor. Very fine pieces of rust can pass through those screens and filters and at times cause havoc.

Re: Failing gas tank sealant
 

Back to the pencil filters........ I use them in every A I have and with great success.


wouldnt run an A without one.

Re: Failing gas tank sealant
 

I'm Paranoid, run a pencil filter, and the in glass sediment bowl screen with a micro filter. Even with the pencil filter the micro filter gets extremely fine particles in it, not sure if the particles would cause any problem in the carb.

Re: Failing gas tank sealant
 

Brent, checking to see if you received my private message about doing tank repair. I'm interested but it seems the message system isnt working between you and I. Or you've changed your mind? Let me know please.