Diesel Tank Cleaning?

[Delancey]

Cheechako- I think you are right not to worry too much about dissimilar metals used in tank fittings. There were stainless screws tapped into the aluminum tank for the sending unit which showed no signs of corrosion when I took it out.

I think the plywood tanks are interesting and I am curious to know what thickness of plywood was used. Epoxy has good chemical resistance. I am assuming there is a layer of lightweight glass cloth over the ply and is the top joined to the sides with a fillet?

I guessing the inspection ports allowed access to finish the interior. The black does look cool but seems like it would be hard to see contamination in the fuel, maybe white pigment on the inside would be helpful for spotting dirt?

[DeepFrz]

I have heard that epoxy is not so great with bio-fuel. I don't know if that is true or not, but was mentioned on the forum a while ago.

[Jbaffoh]

I have a 40 gallon aluminum tank with two baffles. I cut 3 5" holes in the top with a holesaw. The holes are located so I could reach all interior surfaces of the tank and baffles. It took about 2 hours to cut the holes, plus 24 bolt holes, plus deburr the holes and wipe the interior clean, and install my inspection covers.

I made 3 7" aluminum covers with backing plates and internal and external gaskets from buna-n. Essentially, I copied the SeaBuilt system to a tee, except for the custom size and 8-bolt pattern. I purchased all the materials on Amazon--the total cost, including stainless fasteners, was around $48 for all three plate sets. It took a couple hours to fabricate the system without specialized tools.

I drew up the dimensions and took photographs if anyone is interested.

[neilpride]

Beware of a DIY fuel tank, in any insurance or surveyor scenario you are screwed with a ply epoxy tank, for a DIY boat with no regulations, or insurance or brokers in between thas fine. Just saying..

[gonesail]

if the tank is over 20 years old you might consider replacing it while you have the chance to do so .. the sea built inspection ports are great.

[Delancey]

I went ahead and cut a bunch of holes in my diesel tank. Couldn't be happier about it. Cleaned out all kinds of crap I doubt could have been removed without the mechanical action provided by a scrubby pad and some elbow grease.

I would encourage anyone else in a similar situation to do the same. I don't think you could hope to get it 100% clean otherwise. Additionally the inspection ports allow for a thorough visual inspection of the interior. Worth doing if for nothing else than piece of mind.

In my case I found a small amount of pitting on the bottom but not enough for me to think about replacing the tank for another ten years. The small patch of corrosion I found on the outside has been fixed with a blob of weld.

Now for the inspection ports, I have an aluminum backer ring drilled and tapped for 1/4" x 20 aluminum bolts that will be inserted from inside the tank to sandwich the backer ring, a Buna gasket, the tank, another gasket, and then the cover plate followed by aluminum nuts and washers in an arrangement similar to the Sea Built system.

Any thoughts on which to use for a thread sealant for the bolts when they are inserted into the backer ring, Locktite or Neverseize? I guess a case could be made for either one. Does anyone know specifically the chemical resistance of these products to diesel fuel?

[Roy M]

I use Permatex No. 2. It doesn't harden and it's easy to remove the cover plate and screws, years later.
http://www.permatex.com/products/Aut..._2_Sealant.htm

[Delancey]

I've finished the inspection port installation on the fuel tank and have attached some photos. I usually find when I do something new and I want it done perfectly, I usually have to practice first. Hopefully someone else can benefit from my experience.

As before, I started by cutting a backer ring and face plate. In this case some .125 aluminum plate I had access to that seemed about appropriate for the .090 tank. The backer ring was drilled and tapped for 1/4" x 20 aluminum bolts which were inserted from inside leaving studs on the outside of the tank for aluminum nuts and washers.

You probably could get away with stainless without problems. I used aluminum for fasteners because I could. I didn't check because I don't care but they are probably cheaper than stainless anyway.

Inspection port ID being 5" Dia. with a plate OD of 7", this size was about as small as I could go and still get my arm inside the tank. Bolts were spaced about an 1" apart around the plate.

For gasket material I used 3/32" Buna-N 70A Durometer rubber. For those who care to know Buna was invented by the Germans in WW2 as a natural rubber replacement when their access to Asian rubber plantations was limited. It is still used today.

I have a common leather punch but the holes were too small for the bolts I was using. Drilling out the center of a air hose nipple worked pretty good as a 5/16" hole punch. Then the whole thing gets assembled which is where the learning curve happened for me.

The Permatex 2 Form-A-Gasket is a mess to work with. Glove use is encouraged and apply with an acid brush. A friend suggested using it on one side of the gasket only, the part side, not the tank side. This worked well on the first one I did. Because of some carelessness I had a tight fit on a couple bolt holes which meant that the backer ring held itself in place when I installed the cover plate.

On the second one I had proper clearance on all bolts which meant I needed to coat both sides of the gasket so it would stay in place when I dropped the cover down. Alternately if you had a friend who could hold the backer studs in place with a pair of knives until the cover was on and you could get a couple nuts in place you could just coat one side.

If I did it again I would just coat both sides to begin with. I felt like it acted kind of like a lubricant which allowed the gasket to move better when the bolts were tightened down. I dated the install so if the tank ever comes out again down the road we can see if it made any difference between the two.

Finally I did a pressure test with the shop vac and some soapy water. Was it the same pressure as 3' of head I would have if you overfilled the tank? Probably not, but let's just say I'm not planning on overfilling. I'll let you if I have any problems down the road but I'm pretty confident. I used the gasket sealant on the threads on the backer plate and Anti-Seize on the nuts outside the tank just because I had it on hand.

Would I do it again? Of course. Should everyone else do it? Not for me to say. I could have cleaned it using other methods and maybe it would have been fine. For my some things are worth knowing with 100% certainty and this was one of them.

Cheers!

[rebel heart]

Originally Posted by Roy M

I use Permatex No. 2. It doesn't harden and it's easy to remove the cover plate and screws, years later.
http://www.permatex.com/products/Aut..._2_Sealant.htm

I use the same, works like a champ. No idea why people are spending money for "real" gaskets which just end up needing to get trashed anyway. For the amount of times people are opening up their diesel tanks, it's well worth it to just razor the stuff off every few years, clean with brake cleaner, re-apply new.

[Delancey]

rebel heart- I took Roy M as suggesting the Permatex 2 Form-A-Gasket Sealant as just that, a sealant. You are saying you use it as a gasket itself?

Interesting, the directions say apply to one or both sides of gasket. Doesn't say you could use it as a gasket in and of itself but I am still learning.

Seems like the Buna being an elastic material would always be pushing against the clamping force of the bolts but the Permatex is kind of a one way street for being a semi-liquid without any memory. For what it's worth the Buna rubber for the four gaskets was about twenty bucks from McMaster-Carr.

What is the Permatex anyway? It's not a polymer, smells like solvent, dries but doesn't get hard. Any thoughts?

[rebel heart]

Originally Posted by Delancy

rebel heart- I took Roy M as suggesting the Permatex 2 Form-A-Gasket Sealant as just that, a sealant. You are saying you use it as a gasket itself?

Interesting, the directions say apply to one or both sides of gasket. Doesn't say you could use it as a gasket in and of itself but I am still learning.

Seems like the Buna being an elastic material would always be pushing against the clamping force of the bolts but the Permatex is kind of a one way street for being a semi-liquid without any memory. For what it's worth the Buna rubber for the four gaskets was about twenty bucks from McMaster-Carr.

What is the Permatex anyway? It's not a polymer, smells like solvent, dries but doesn't get hard. Any thoughts?

Yes you can use it as a gasket in lieu of a "real" gasket, at least I have with fine results. I'd use a different version though; they have this stuff (what I use) which is the actual "gasket maker" and is recommended for oil resistance.

Permatex 81724 Sensor-Safe Ultra Blue RTV Silicone Gasket Maker,3.35 oz. Tube : Amazon.com : Automotive

[boden36]

Rebel Heart,
If you use Permatex, does it glue the lid to the tank? If so, how do you get it off again?
Regards,
Richard.

[rebel heart]

Originally Posted by boden36

Rebel Heart,
If you use Permatex, does it glue the lid to the tank? If so, how do you get it off again?
Regards,
Richard.

It has about the holding power of any other silicone so a flat head screw driver will pop it loose easy enough. It glues it down, but not really, if that makes sense. Certainly not epoxy or "real" glue. It dries pretty flexible.

[Ironhorse74]

If you are talking permatex blue glue, it is just GE silicone sealant colored blue. Back a long time ago when I dealt with John Deere, they used to put a quarter inch bead on the valve cover and then let it cure. It then went on the engine with no gasket. Not sure I would trust that method on a .090 aluminum tank though.

Brad

[sartorst]

DONT use silicone on fuel tank applications, oil yes, fuel NO!!