Gas tank leak

81 F150 Ranger. When I fill up the middle tank it leaks from the top front of the tank. Somewhere near where the vent line goes to the engine compartment. There's a good amount of rust on the frame there and some melted rubber where I'm guessing the fuel is dissolving the gasket around the tank. I can blow through the vent line and it seems unplugged. The rubber vent line seems good too. Can the metal tubing be bad?  So hard to see and I'm thinking a PITA to replace IMG_20230506_122059.jpg

The large o-ring that seals the sending unit to the tank was leaking on mine.  I lowered the tank by loosening the all-threads that hold it in and then was able to turn the wedge ring to remove the sending unit, replace the o-ring, and put the wedge ring back.  That fixed it.

Maybe my pics aren't posting but there is a pretty thick layer of rust at the front of the tank.  I think there's a hole there.

I see the pic and the rust.  But assumed that was the bottom of the tank and you said it leaks from the top.  So, is that the top?  And that's where the leak is coming from?  If so then I agree there's probably a leak there.

POR makes a fuel tank sealer that should stop the leak, although I've not used it so really can't say it will.

Yes, that's the top,  front. When park the drip circle will be 10in across in 5mins until the tank level lowers enough...

Take a look inside.
I'd consider a new powder coated tank.

I replaced my midship tank and new straps for ~$150 last year.

I guess it ultimately depends on how much you value losing your truck to a fire.
IMO it's an opportunity for cheap insurance.

I ordered a new one today and it'll arrive tomorrow. It's too inexpensive to not just replace it. When I got the truck,  I was told not to use my rear tank. Gauge and tank switch work. Must be some debris in there. So easy to get to that one that I'll try to clean it out tomorrow.  It'd be nice to have both functional. Thanks for your help again!
Ray

What's the concensus on using an inner tube for the strap liners on my new gas tank.  The old ones were toast,  no idea what they were made from. Parts houses don't have listings for the liner either.
Ray

Rubber is not really a problem (unless it gets gas or oil on it)
Seems a lot of people here have used strips of edpm roofing too.

I always thought the woven straps would hold water and promote rust but maybe they are specially treated?

I don't know anything about the woven straps. Unless you're referring to the liners. I'm worried the liners will eventually wiggle out. There looked to be a fiber pad between the tank and the body.  It looks like cardboard but it's 50 yrs old too

Raywilson wrote

I don't know anything about the woven straps. Unless you're referring to the liners. I'm worried the liners will eventually wiggle out. There looked to be a fiber pad between the tank and the body.  It looks like cardboard but it's 50 yrs old too

I just recently replaced the single tank on my 86.  I cut some strips of roofing felt and used that to replace the original pad.  I doubled it up since it was thinner than the original.  Not sure that's the best solution, but it worked for me since I had leftover material from a shed I recently built.  

That's a good idea. I had an old T bird that had what seemed to be 30lb pound felt on it's gas tank.

Interesting!

My '87 came with some kind of webbing, about the same as you find in a 10,000# ratchet tie down.

I've seen what looks like roofing felt but I just assumed it was from a previous owner repair.

I run into this often. when resurrecting an old truck, I always expect to replace the tank. as earlier said, it's way too affordable to not do it. replacing the sender with one by the same tank vender is also smart as it "usually" means better fitment.  however, none truly come calibrated. it's going to need to be done at installation. I have three to do now as time allows. but as far as the rubber / fiber membrane found between the tank and frame, I use a product readily found at a home center in the roofing section. it is a roll of foil faced, self-adhesive epdm flashing about a 1/16" thick. I measure where the tank fits to the frame and stick it to the tank first. normally a piece about a foot long. then I line the straps with it along the lower flat /level area and up each side about two inches. this works awesome! I do the same for rear tanks as well by putting longer strips front to back where the tank meets the upper straps then coat the flat braces with the same. no squeaks. no metal-to-metal contact and aside from the odd chance of moisture which dries off quickly, no moisture retention. and btw, one roll can last year's even if doing many tanks. around 20 dollars last I bought one.

Ray, I recently replaced my front tank and LMC has what they call anti-squeak strips. My original strips appeared to be 30lb roofing felt and were worn thru. So anti-squeak means movement and it shows on mine. I believe 4x4 guys would need something better. The felt type material lasted at lease 30+yrs on mine. Since it rains between cab and body on top of tank, I coated the tank with 3M Undercoat.