Gas Tank Rehabilitaton

Even big holes aren’t a problem if you take your time

When I removed the gas tank from my project car I had to evict a family of field mice. A big mouse picked up one of the babies and ran away, leaving other babies to fend for themselves.  In a rare moment of kindness to rodents I gently put the remaining babies outside and hoped the mom or dad would find them.

While that was sad, sadder still was what they did to my gas tank.  Years of exposure to mouse excrement and moisture left my tank with holes and rust, which became readily evident after some sandblasting.

Lots of holes near the mouse nest location

Some holes up to 6mm (1/4")

This might be tricky to fix

Rot-O-Rama!

What are the options for fixing a Heinkel gas tank? I was hoping I could pull it out, clean it, repaint it and be done, but this tank needed far more work. I researched purchasing a new one but they’re not reproduced (although that might change very soon), and old ones aren’t easy to find, need work themselves, and are not inexpensive to ship from Europe to the USA.

My remaining options were to fabricate a tank from scratch, send it out for repairs, or try to fix it myself.

Let’s analyze each option: 

Fabrication: Even though I now have metalworking tools, I don’t have the skills to build a tank. I could try to have one fabricated, which was an option, but the price would be astronomical.

Firm specializing in fuel tank restoration: My next thought was to send it out to a restorer. The trick here was to find someone who would actually do the work. In a metropolitan area of almost 5 million people I found exactly one company that would consider looking at it. The estimated cost from the photos I provided was about $400. I’d also have to travel far to drop it off, pick it up, wait, etc. I temporarily ruled this out as too time consuming and expensive.  

Me!: So, like a lot of Heinkel projects, it ended up being a job I had to do myself.  My first thought was to weld up the tank and then seal it. I was quickly discouraged from this; everything I read said NEVER weld a tank for fear of explosion- even old tanks.  I reached out to a few old timers and they said don’t try it at home unless you want to risk an explosion.

My remaining option was to use a gas tank restoration kit and patch the holes. I’ve repaired several motorcycle and scooter tanks using either Kreem, POR-15 or KBS. KBS and POR-15 are very similar, and I prefer them to Kreem. Of the two I like KBS the best. KBS has online tech support and for what seems to be essentially the same product is about 10-15% cheaper than POR-15.  I think you get a little more paint in the kit as well, so the decision was pretty easy for me.  Also, if you buy at the right time (like Black Friday) you can use a coupon and reduced shipping.

Here are the kits I looked at:

KBS: https://www.kbs-coatings.com/large-cycle-tank-sealer-kit.html

POR-15: http://www.por15.com/POR-15-Motorcycle-Fuel-Tank-Repair-Kit-_p_106.html

Kreem: http://www.kreem.com/fueltankliner.html

How the tank sealer kits work:

The process for an old tank without holes is pretty straight forward: Clean out the tank, etch the tank, and then seal the tank. You need to follow the instructions and take your time since a mistake may mean you have to start all over again with a new kit.

Holes cause complications:

The added complication for me was the holes, some of which were 6mm (1/4”) in diameter. All of the steps listed above involve soak time, and since my tank wouldn’t hold liquids I had some extra work to do.

Here’s my Step-By-Step Process:

1. Clean and etch the outside of the tank: The paint needs a high adhesion surface, which you get by using the acid etch that comes as part of the kit. I used the etch on the outside first.

2. Plug the holes with epoxy: I used stick epoxy to fill the holes.

You cut a piece off of the tube, then roll it in your hand to mix the parts, and apply it. There are many different brands, try to get one that says it is fuel resistant.

Tank with epoxy filler dried and sanded

3. Measure and cut reinforcing mesh to size: I ordered some extra material called “backbone” from KBS. It’s a fiber mesh that is easy to cut. I cut a piece to cover the entire bottom of the tank.

Cutting and Fitting the Mesh for Heinkel Trojan Tank

4. Paint a base layer of tank sealer: Open the can, stir (don’t shake), and apply a layer with a disposable brush. I also suggest using a respirator and doing the work in a well ventilated area. The paint contains cyanide (technically isocyanates) so you are best off minimizing your exposure.

5. Apply the mesh: With a good base layer of paint, stick the mesh into the fresh coat. Apply another layer of tank sealer right away. Give it a minute to make sure you do not have any bubbles. Keep an eye on it as mine would bubble up a bit as the paint cured.

Layer of Sealer and Mesh

6. Wait a week: Let what you’ve done DRY THOROUGHLY. Surely you have other things to do!

After a week you now have a tank that is structurally sound but is still gross and rusty inside, and may still leak. Now it’s time to use the tank sealing kit in the way it was originally designed.

7. Clean the inside of the tank: The kit comes with a cleaner that will dissolve most of the dried on gas and goop in your tank. The directions suggest throwing in some nuts and bolts to help loosen rust and deposits. If you fixed the outside of the tank like I did, DO NOT DO THIS. I found that the nuts and bolts knocked the epoxy hole plugs out of place. Not only that, the acid in the wash started to eat away at the paint.  

You can see where the acid etch started to dissolve the sealer

A good way to seal the fuel filler and petcock hole are with a rubber glove and rubber bands. They work quite well!

Use a rubber glove to seal holes

8. Etch the inside of the tank: Now etch the inside of the tank just as you did the outside of the tank. After you etch the tank let it dry for a FEW DAYS.  

9. Seal the inside of the tank:  Apply some WD-40 on the petcock hole threads so any misapplied sealer paint can be easily removed. Mix the sealer paint (don’t shake, you’ll get bubbles) and then dump the can into the tank. Slowly roll it around for 30 minutes, changing the position every 5 minutes so the entire tank interior gets covered. This is easier said than done; the Heinkel tank has two interior  stiffeners that run from front to back, and it’s a little tricky get these covered. After 30 minutes lay the tank flat and let excess sealing paint drain from the petcock hole into the original paint can.

In my case I found that my tank was not liquidproof. Several leaks appeared in the bottom of the tank from where the epoxy plugs were knocked loose. These would need to be patched again.

You can see where the leaks are as the interior sealer leaked out

10. Re- patch any exterior holes: You’ll need to get to this right away because the paint doesn’t have much of a shelf life after you’ve coated the inside of the tank. I cut out small bits of mesh and followed the same procedure as before- painting and patching.

11. Paint over the tank sealer: I wasn’t exactly sure how to do this, so I contacted KBS Tech support. They directed me to lightly scuff the dried tank sealer paint with 320 grit sandpaper, and then paint with standard etch primer paint.

 

Tank painted- you can see the second set of patches

I didn't notice the dings until I painted

Now that the tank is complete and ready to use I suggest putting in some liquid and making sure it does not leak. We’re lucky that Heinkels have a layer of insulation that will allow a slightly uneven surface such as the patched tank to be installed without a problem.

Are Reproduction Tanks on the Way?

They might be. The UK club has commissioned and evaluated a prototype made by the same company that reproduces Heinkel bumpers and exhausts. The word is that it passed the test. I have no idea how much they are or what they will cost. Yet another reason to join the Heinkel Club of Great Britain.