Bubbles above gas tank
 

I bought the car knowing this. I drained the tank and flushed it and it's pretty clean with no rust showing up in the clear sediment bowl. The car sat for two years before I bought it with about a 1/4 tank of old gas in it. I'm assuming it's from moisture in the tank and sitting. I'm hoping it's not something worse. I have since filled the tank to almost full and no further bubbling.......


Can a good repainting (at some point) fix this? I'm hoping the tank is ok...




Don

Re: Bubbles above gas tank
 

There’s something under those bubbles.

Been storing Model A’s for years, moisture in the tank should not effect the outside.

I think you have another problem here.

Re: Bubbles above gas tank
 

Maybe a defect in the paint and body filler??

Re: Bubbles above gas tank
 

I'm not a body work expert but my guess would be the same as WHN. Maybe rust bubbles? Also, isn't the tank on 28-29s separate from the cowl? My 30 has some bubbling right around the filler but I'm almost positive that's from gas attacking the paint.

Re: Bubbles above gas tank
 

I can deal with it being paint issue and maybe some rust. But it's just strange that it is only in this spot and no where else on the car. If there is a space between the tank and the cowl, why couldn't moisture from a half empty tank migrate into that air space and thus cause this blistering? Yes, the car is a 1928. I'm hoping someone knows what this is from past experience.

Re: Bubbles above gas tank
 

There is only a space between the tank and cowl on cabrolets and fordor sedans. Coupes, tudors, roadsters, phaetons, pickups, the top of the cowl IS the tank. You did not say what body model you have. It looks to me like the area was not cleaned well before painting.

Re: Bubbles above gas tank
 

It's the phaeton in my avatar. So. if it's a defect, I can deal with that eaiser than a tank issue. :o

Re: Bubbles above gas tank
 

You may have to open one of the bubbles to see if there is rust formation under the primer (which is not always moisture proof when initially applied) or under body filler in that area . Agree with others that those may be lifting under the primer. Do you know what type of paint you have ? Does paint come off with polishing ? It could be lacquer or some other single stage.

Re: Bubbles above gas tank
 

At this juncture (I'm the new owner) I'm going to wait until I can have a body man explore and fix the problem. My biggest concern was a gas tank problem, but it doesn't leak, looks good when I drained it and inspected it as much as I could, had no real rust flakes showing up in the sediment bowl, but removing the tank if this was the remedy and problem, was not something I wanted to tackle right now. I'm still working on the new radiator which is coming, but the bubbles were a mystery ever since I bought the car in late summer and I posted the pic to get some answers. I feel a tad better about it after reading some posts here. The original owner thought it was a body filler/paint job problem.


Paint dosn't come off with polishing.....to answer that question. Not sure what kind of paint it is......

Re: Bubbles above gas tank
 

It's difficult to tell from those pictures alone what the problem is. Maybe rust from inside the tank has broken through, maybe a fault with the paint. To clarify which it is, I'd drain the tank till the fuel is nearly empty or completely empty, remove it and use an optical fibre camera to look inside. If there is no heavy rust, the problem is the paint. If there is heavy rust give it a poke and see if it is through the metal. You might also try pushing in those bubbles with a finger nail. If they're soft, the paint is bad, if hard, most likely rust.If I wewre forced to make a guess based on the pics, I'd say "paint". How's the paint on the reat of the car?

Re: Bubbles above gas tank
 

How soft is the metal in that area? Can you push it with your thumb?? (-Not the bubble itself but the surrounding metal. )


I have seen something similar on two different tanks where both tanks had been cleaned with muriatic acid by the owner and the metal had a tiny pinhole develop under the paint because the acid just kept eating at the metal. Not to scare you, but if the metal is soft in that area, that is likely the culprit. If the metal is firm and you are able to see moisture under the paint bubble, I would suspect there is a small hole that gasoline vapors are seeping into. That is more easily repaired.

Re: Bubbles above gas tank
 

I'm surprised at the number of people who think using muriatic acid to remove rust is a good idea. As Brent said, that acid never rests. I stored a gallon of muriatic acid under the laundry tub in the basement, and even though the gallon jug was always capped, the 4 steel legs on the laundry tub are rusting away. Just the fumes can rust any steel within 10 feet of it.

Re: Bubbles above gas tank
 

Hmmm....... I'll give it the fingernail test tonight.

Re: Bubbles above gas tank
 

Would incomplete surface preparation before a repaint cause this?


Since the paint bubbling is in the area of the fuel filler, perhaps previously there was a lot of gas paint damage. Perhaps even down into the metal. If not thoroughly prepared, possible bubbling.

Re: Bubbles above gas tank
 

Whats' funny is that no one has really said, "yeah, that is from_____ as I had the same problem". I can Imagine rust but why there? The rest of car is virtually rust free. If the tank were that bad, it would have leaked, one would think. I still think it's moisture from a half empty gas tank some how affecting the body filler or paint or just the metal in the cowl, but again, I'm guessing, until I bring it in to be fixed and the body guy says what it is after he grinds it all down. Either way, I will have to wait until next summer. :cool:

Re: Bubbles above gas tank
 

A lot of times there is no one correct answer when just looking/hearing/observing something, it is a best guess. The root cause may only be found during the repair, if you are lucky. Some issues can have more than one cause, and you may never know definitively your issue's cause. The issue may also have been caused by multiple things. Everyone tries to help, from their own experiences/knowledge/opinions, which gives you options.

Re: Bubbles above gas tank
 

I agree.....after restoring 3 old houses ;) Until you start ripping and tearing......you just never know what lies beneath. And why I'm a tad worried about what this might be. I was hoping for a clear cut.....yep....its ______


Like I said, the body guy will know once the repair begins. I just pray it;s not the tank.

Re: Bubbles above gas tank
 

One thing stands out in the picture.....the bubbles are in a circular pattern of sorts and a way from the filler cap quite a bit. Is there any bracing in the tank under there like that??


BTW...I do appreciate any and all thoughts here.......always have.

Re: Bubbles above gas tank
 

Here's a picture Brent posted of a 1928-29 gas tank.


Bob

Re: Bubbles above gas tank
 

I wrote the owner this morning about all this and his reply "Hi Don. I am sure that is bodyfiller, painted cars my entire life and worked for a paint company for 26 years. It looked like that when my Dad bought it, I think it was around 8 years ago.
Our roadster pickup had leaks across the entire bottom of the tank, I had to have the tank welded and coated. When the tank was welded the heat distorted the top of the tank. I had over 60 hours in straightening and repainting the tank. I had to use body filler to level the top of the tank. The "trick" is to seal the paint edge around the filler neck to avoid the fuel getting under the filler or between the paint layers."


So.....it's looked like that for 8 years or more. Seems like rust would have progressed.



He's been really nice with my many questions and concerns long after this sale and he writes occasionally asking how I'm doing with the car. That says a lot.