Gas tank leak...

[Oonrahnjay]

...  Got a bus you would like to get rid off? ...

  BK 

    Don't we all, a fair amount of the time?   

[shelled]

Long ago when I was actively trading Corvairs and first generation Mustangs, I used to repair SMALL gas tank leaks.  I would never ever use a wire wheel because of potential sparks or heat.  I would never ever tilt the gas tank so the highly explosive vapors were at the leak point.

I used 3M green Scotchbrite and a plastic repurposed ice scraper to clean the outside of the tank at the leak.  I used generic gunk sold at auto parts stores which gets worked into the leak to seal the leak itself.  As a belt-and-suspenders follow on, I wiould cover that with a scrap of fiberglass cloth loaded with JB Weld.

I still have a 1966 Corvair that Was one I did this to and it hasn't leaked a bit in over 30 years.

e3

[dukegrad98]

Unsafe at any speed!!!   

Cheers, John

[chessie4905]

   Since we are dealing with fuel oil this won't be a problem. If there is concern, you could use a wire wheel with brass bristles. One of those hand held sandblasters will work also;just don't get carried away and create a new location to drain the tank.

[rampeyboy]

I got lucky with the fuel leak on my Scenicruiser. The steel drain plug rusted away until the exposed part just fell out! New plug screwed in and tightened with no issue. Good luck with yours.
Boyce

[Geom]

Hmm, somehow I think I managed to lock this thread. Not sure how, but I managed to unlock it 

Anyway, I wanted to provide an update on the tank issue.

B_K, thanks a lot for the info on Sam. Not sure if you know him personally, but he's been great! A real bus guy. I got further with him in 5 minutes on the phone than over a week with the other two guys, LOL.

So, he had it in his shop and looked it over and no matter what he did, he could not get it to leak. And he checked it pretty throughly and had it lifted in his shop for days.

I had noticed that by the time I took it over to him, it had stopped leaking completely. I attributed that to the possibility that the hole/leak was now higher than the current fuel level, since we'd been driving it back and forth to mechanics and such.
So I advised that Sam put in some fuel and see if it starts to leak again. He filled the tank to the neck yesterday and it sat all day yesterday and today; and nary a leak.... 

So I picked it up today and took it home, as there is really nothing further he could do. He offered that he can take the tank down, but advised that it seems unnecessary as the tank looked fine and I agreed.

So now I'm really confused. I know it was leaking. I could clearly see fuel. By the time it got to the first mechanic it had seemingly slowed down. By the second mechanic I don't think it was doing much at all. By the time Sam got it, it had stopped completely.
There is a full tank in it now and it's still not leaking.

My only guess is that its inability to vent, completely, creates a negative suction that is stressing a weakening seam? We filled it up and drove it a long distance. Then we parked it and didn't touch the tank (as where we had been constantly messing with fuel on our trip back). So it sat there for a while under negative pressure, and that's when it started to leak. At some point later I opened the tank cap and it equalized (the whoosh I heard). Not sure if that's possible or what happened... Anyway, it's the best guess I can think of. 

I'd love to hear what others think.

For now I'm not going to worry about it and hope that it just goes away on its own (yeah right), LOL. I will check on it over the weekend and see if it stays dry. It's in its storage place now and where it's sitting has a bit of an incline towards the driver's side. So we'll see
But it does have me scratching my head 

Thanks
George

[eddiepotts]

I think WHOOsh cold be one of two sounds. I would guess your pressurizing from heat instead of going vacuum. You may just need a new fuel cap or vent. I would think you could be leaking from a fitting. When things are in vacuum fluid goes in, under pressure fluid goes out.

[Jim Eh.]

Wouldn't lack of tank venting should have cause fuel starvation to the motor?

[RJ]

George -

Hope you're not putting gasoline in the fuel tank!   

Another option, besides Luke, and closer to you, is JD at C&J Bus Maintenance up in MN.  IIRC, they're in a suburb of Minneapolis.

FWIW & HTH. . .

[Utahclaimjumper]

It maters not if its pressure or vacuum,, you need a VENTED tank (or cap).>>>Dan

[luvrbus]

I don't know about the GM but most are vented at the filler neck through the cap I never saw a vent on the tank myself

[Geom]

I'm pretty sure it's holding negative (vs positive) pressure. The sounds it makes sound distinctly like a sucking sound 

I'm inclined to agree that negative pressure would hold the fluid in, not push it out. My thought on that was the negative pressure was flexing the tank such as allowing fluid to seep through a spot in a seam. But I honestly have no idea

As far as fuel starvation, it doesn't seem to be affecting fuel delivery at all. We filled it completely, and emptied half the tank enroute and it ran without issue. I'm guessing the fuel pump is overcoming whatever negative pressure is being created.

RJ, thanks for the info on JD. I will be sure to check him out if we're near the MN area.
I really liked working with Sam. He's a good guy to talk to. He seemed to... get buses. He has a huge graveyard of poor old MCIs that have clearly seen better days. So he's very comfortable around these babies. He unfortunately doesn't do routine maintenance type stuff (too busy, too old, and too much going on, to quote him ). He does however work on the stuff "no one else is willing to work on". I think he enjoys the challenge, lol.

Clifford, I think you're right. I don't think the tank is vented anywhere but the cap. The cap is one of those attached to a pivot point, with a big double-action handle, directly to the neck, heavy duty looking things. I may have to rig up some sort of homebrew vent for it by drilling a small hole (without blowing myself up, lol), in the cap itself.
I'll also inspect the current one further and see if there was ever a vent that is now blocked on it. I assume at some point in its life it was vented

Thanks again all,
George