Fixing a hole on top of the fuel tank.

[Brian894X4]

OK, so I made a colossal mistake and it’s pretty darn embarrassing to have to fess up about it, but I need some advise.

Basically, I used some short screws to bolt a box to my driver’s side passenger floor and the fuel tank was closer to the floor board than I realized. Apparently, it’s right up against the floor board. These screws were only about 1" long. I should have known better and I'm kicking myself up and down right now.

The hole I made is extremely small, but it’s enough that it needs to be repaired and that means dropping the tank I’m sure.

So, my questions are does anyone have any advise regarding dropping the tank? I can see the exploded diagram in the manual and my thoughts are draining the tank using a drop in hose into the fuel filler (I don’t want to undo the plug if I can avoid it) . Then undoing the fuel filler rubber hose, then unbolting the sending/fuel pump unit from the tank, pulling it out of the tank and leaving it hanging up by the body as the tank drops down.

Looks like there’s some gaskets I’ll have to replace as well. Maybe put a few fuel filter in, since I’m already there.

Does this sound like a plan? I’m afraid I’m overlooking something. My biggest concern is dropping the tank and how heavy it might be.

Finally, once the tank it out, what’s the best way to fix the tank. It should be just a very small hole. I’m wondering if I should use something like JB weld, or RTV or some combination or is there something better? Once I get the tank out, I want to do it right.

Thanks, I'd appreciate any advise.

 

[mudking82]

My biggest concern is dropping the tank and how heavy it might be.

Since you just have small holes in the top, if it was me, I would keep driving it to get the gas low, then drop the tank. Unless you have a way to siphon it out. Or you could drill another hole in the bottom and drain it. Just kidding. Don't know about the repair though.

 

[Brian894X4]

Actually, I'm thinking I might try to repair with the tank in place. I was able to widen the floor sheetmetal hole a little bit to get a better view and the hole in the tank is extremely small. I think I can use some gas tank repair puddy or some special RTV to fix it. If anyone has any suggestions....

The tank is literally about 1/8" below the sheetmetal at this particular point and the floor sheet metal is only about 1/16" thick. Definately not double walled. Word to the wise. Which clearly was not me.

 

[PKP80]

whatever you do just don't weld it, lol. BOOM

 

[haffi]

What about using a new a little thicker screw and some kind of adhesive with it? Cover the hole with JB-weld and then screw in the screw, leave it there and forget about the whole thing?

 

[MoJ]

Don't feel too bad...others on here have actually done the same thing. There should be another thread out there somewhere but I don't recall how they fixed it.

 

[Doc]

whatever you do just don't weld it, lol. BOOM

You can weld on a gas tank, but the trick is to keep it full at all times IIRC. Gas itself isn't too explosive, its when the gasoline becomes vapor that you have to really worry about it.

Anyway, I'd JB weld the hole and call it good.

And maybe duct tape. No repair is any good without duct tape.

 

[mudking82]

They do make a special repair putty for gas tanks. If you can reach the hole, that is what I would do. Check out this ebay link for an example of one made by Permatex. eBay Motors: PERMATEX GAS TANK REPAIR INSTANT (item 200194471503 end time Jan-29-08 14:19:24 PST)

 

[Brian894X4]

Yep, I have that and I'm going to use it to try to repair, then cover over that with Permatix No. 1

That should do it. Hopefully.

 

[gray]

I used the two part epoxy on a tank that developed a leak at a spot weld; worked fine. I would not just run a larger screw in the hole; the next owner would have a big surprise when/if he tried to pull the tank down. Wouldn't want to weld on a full tank of gas; maybe no boom(at least initially) but might get a little flame thrower action going (heat, increased pressure, a spark, a hole---). Have heard about draining (easy to do if yours has a drain plug), then cleaning, even purging with nitrogen, before welding.

 

[Brian894X4]

It's almost fixed. Fortunately, just one small hole. The other screws missed. So, I opened up the floor hole about 1/2" to get access to the top of the fuel tank, and cleaned out the hole and top of the tank, then used the Permatex tank repair. Once that completely dries, I'll goop the crap out of the top of the tank, through the floor with Permatex No. 1 and then close the hole. There will be pressure on the repair, so little worry of it popping out. The space between the floor and top of the tank is literally about 1/4" inch, in this particular location. In some spots there's more clearance, in others the tank is up against the floor with a very thin piece of rubber seperating the two.

I didn't realize this, but Toyota actually bolted the tank to the body and it's sitting up against the floor pan. On my Toyota mini-truck the tank is bolted to the frame. Huge difference there. One advantage on the LC is they were able to get a lot better ground clearance, than say...the earlier 4Runners.

On another board, there was some concern of fuel tank pressure affecting the repair, but I think this should be OK. It will be much stronger than having just the screw in there and that worked fine for a while, before I realized what I did.

The repair will essentially be overdone, so I think this should do it. And lesson learned. No more drilling or screwing holes.

 

[Brian894X4]

For some reason I was thinking that the tank would be under pressure from the inside out and working my repair on this assumption, but obviously, this can't true, or fuel and vapor would come out every time you opened the filler.

In fact, the fuel tank is not under pressure, but under vaccum, right?

The vaccum I assume is simply from the fuel level lowering, but no air being allowed to get inside. The lower the tank, the higher the vacuum...right?

So, the problem of blowing or in this case, sucking in the repair is still an issue. But the problem of potentially blowing out fuel and vapors is less likely now.

So, I figured the hole is about 1/16" or less. So, that means I could fit 256 holes that size in a square inch. Why this is important is to show just how little pressure or vaccum is being exerted on that hole. I could have this all wrong, but whatever the fuel tank pressure or vaccum is, you have to divide that by 256 to get the actual pressure being exerted on the repair.

For example, if the fuel tank was pressurized (since my feable mind can calucate pressure easier than vacuum) to 34psi, the actual pressure on being exerted on the repair point would only be 2 ounces of pressure. Which is definately not much, and I'll bet the vacuum/pressure of the tank is far less.

I could have this all wrong as math is not my strong point at all. Does anyone know what the typical vacuum/pressure is inside a fuel tank, or at least the maximum vacuum? It can't be too much or the tank would collaspe in on itself. At the very least the rubber hoses would collasp, yet they don't, and the cap would be hard to get off, so vaccum must be minimal. Which means the affects of pressure/vacuum on this repair would be VERY minimal.

So with that in mind, this repair seems far safer than I first thought. Heck, chewing gum or duct tape would probably fix it just fine, not that I'd use that....

The epoxy I have is impervious to gasoline which would be critical.

 

[gray]

The tank normally builds up some pressure, but the epoxy can handle it IMO. Years ago my 62, when almost new, developed a very high pressure situation and a leak in the gas tank. I brought it to the dealer (after the 12 month/12K warranty) and they said, sorry it's your problem; a new tank will cost you one million dollars----. So, I bought a two part epoxy made for gas tanks, the type you mix together like putty, and pushed it over the hole just like a wad of chewing gum. That held for over a year. Then I get a letter in the mail; Toyota was recalling all the tanks in all the 62's due to, you guessed it, leaks and high pressure. I got a new tank out of the deal. Point is, the epoxy worked, even in a tank that had abnormally high pressures.

 

[Brian894X4]

Good info...so what caused the pressure problems?

 

[knorrena]

What about putting the tank repair in the dimple and driving a screw into the hole? The chemical seal would act like a gasket for the screw.

Karl