Best way to repair fuel tank leak

[Alan L]

There I was sandblasting a bit of rusty exposed fuel tank, where the seal had been scraped off in a previous era.
When fuel started piddling out. I now have a hole about the size of a pin head. What is the best way to repair it?
Thanks
Alan

[ClickClickBoom]

Buy a good used one. With a very few exceptions, it's cheaper and easier. I know from personal experience.

[Bill Douglas]

Yes as click click said a new one. Tip of the iceberg stuff. Lots of pin head sized holes just waiting to bust out

[Alan L]

Hi Bill. And where exactly do you think I might find one guys (looking at you Bill - bit scarce down under).
Alan

[Bill Douglas]

One of those guys who part out cars on Trademe?

[Alan L]

Had a go at the only one listed F/S. But it had to be collected. That meant a 600+Km, 2 day round trip.
I have just persuaded him to ship it.
But he is in Oz at moment.
Would still like some info on best way to repair tank if possible. The one I've purchased is same age as the one that just leaked, so the same issue is likely to surface sooner or later.
Regards
Alan

[porterdog]

1. In the vintage motorcycle realm rusty tanks are commonplace; I believe the go-to solution in that market is called Kreem. Never used it, just hear about it a million times.

2. I've had long-term success repairing external trauma to metal tanks with epoxy.

[ClickClickBoom]

Porsche 911 (1974-1989) - Fuel System - Page 5

[Alan L]

Thanks Porterdog - will try and follow that lead up.
Clickclickboom, if I lived in the US and could buy a new tank for $400 it would be a no-brainer. But by the time it gets shipped to NZ you could probably multiply that 3X - based on previous experience of all the bits I've shipped in.
Regards
Alan

[E Sully]

You can't use the tank sealers on the 1973.5 and later gas tanks, inluding the later Motronic. It will clog internal lines and eventualy peel off the internal whirl pot and block fuel flow. Finding a good used or new replacement tank is the only way.
CIS Gas Tank

[Texel]

If the rust has started from the outside (salt etc) rather than inside.

Tank out, paint strip the bottom, coat any rust with phosphoric acid (eats rust at 10x the rate of steel), leave overnight.

Wire brush the now soft rust residue, look for holes or depressions that will turn into a hole.

Wash out tank with water, run water through it for a few hours.

Connect up car tail pipe with hose and run carbon monoxide through the tank when doing the next step.

Using conventional brazing rod, fill all holes etc.

Go to Wurth store, get various rattle cans of primer, thick underside sealant etc, they have a wide range and you can get a good match on the original with a bit of experimenting.

The bit below is more for viewers than the original poster as I can see this thread going pear shaped......


If you are of a timid dispensation and the throught of welding on a gas tank is a bit scary then don't do it.

If on the other hand you have a peek down the front of your undershorts and you can find a set of stones, crack on!!!!

[Alan L]

Nice link Ed. Thanks.
Still want to find a decent repair option if possible. My replacement tank of same era is bound to run into same issues.
regards
Alan

[Alan L]

Thanks Texel - that is what I was after - our posts crossed. Wondered if brazing was a useful option. I have all the gear. Your flushing method looks great. Thanks.
Alan

[Ian Comerford]

I used soft solder on mine twice, lasted about four years from when it first leaked but you have to accept that it is likely to carry on rusting inside and will clog up the fuel filter eventually. I cut open my fuel filter after four years and the rust deposits made me realise it was time to change.

Ian

[JohnJL]

Originally Posted by Texel

If the rust has started from the outside (salt etc) rather than inside.

Tank out, paint strip the bottom, coat any rust with phosphoric acid (eats rust at 10x the rate of steel), leave overnight.

Wire brush the now soft rust residue, look for holes or depressions that will turn into a hole.

Wash out tank with water, run water through it for a few hours.

Connect up car tail pipe with hose and run carbon monoxide through the tank when doing the next step.

Using conventional brazing rod, fill all holes etc.

Go to Wurth store, get various rattle cans of primer, thick underside sealant etc, they have a wide range and you can get a good match on the original with a bit of experimenting.

The bit below is more for viewers than the original poster as I can see this thread going pear shaped......


If you are of a timid dispensation and the throught of welding on a gas tank is a bit scary then don't do it.

If on the other hand you have a peek down the front of your undershorts and you can find a set of stones, crack on!!!!

That last line got me. Nicely played.
the easy way is with Kreem inside and JB Weld outside. Beware though, its never just one pinhole...

[catuck]

Don't use tank Kreem - that stuff is horrible. I used it on a motorcycle tank once - ruined the tank. I did use JB Weld on my Porsche tank a few years ago - it's still holding up fine but I just bought a good used tank to replace it.

[Trackrash]

I repaired two old VW Beetle tanks with permanent success. HOWEVER, the rust was confined to a small area at the bottom near the fuel line. There was not any rust other than at the very bottom BELOW the fuel line where moisture would accumulate.

I made a patch out of COPPER sheet and SOLDERED it over the area.

I would only attempt this sort of repair if the rust is confined to a small area.

[Alan L]

Hey guys, just pulled tank and had a good look inside. It is mint inside. Not a speck. All external.
So... JB weld, or braze? I suppose if I go JB first and it doesn't work, I can always braze?
I have big stones - I track a 930. What else do you need? :-)
Thanks
Alan

[Ronnie's.930]

Hi Alan - I roadraced motorcycles for 10 years - many crashes and gouged tanks throughout the paddock - JB Weld worked perfectly for small repairs time and again.

[Alan L]

Originally Posted by Ronnie's.930

Hi Alan - I roadraced motorcycles for 10 years - many crashes and gouged tanks throughout the paddock - JB Weld worked perfectly for small repairs time and again.

mine is on bottom side of tank. Does it stick OK - won't fall out?
Does it fix broken bones too? :-)
Regards
Alan