1963 Mercedes Benz 190DC Fintail. Bad fuel tank and leaks.

[jim89]

8 hours ago, lisbon_road said:

Many years ago, I fitted a new tank to a Sierra. I did not realise that the inside was bare steel. It rusted horribly. If I did it again, I would use a tank sealant on it. Kind of counter intuitive to use on a new tank, but the steel is so clean tgag it should stick.

Your experience might be different but I have to share mine.

Is it necessarily going to be "that clean" though?

I'm wondering if there could be traces of lubricant from the pressing of the shaped "halves" that have also been (presumably) welded together?

Hopefully it's flushed with something at the factory to remove "bits" & the worst but whether that could be classed clean enough to paint straight onto ? I dunno...

[Dyslexic Viking]

9 hours ago, lisbon_road said:

Many years ago, I fitted a new tank to a Sierra. I did not realise that the inside was bare steel. It rusted horribly. If I did it again, I would use a tank sealant on it. Kind of counter intuitive to use on a new tank, but the steel is so clean tgag it should stick.

Your experience might be different but I have to share mine.

I've been thinking about painting the outside and rust-proofing it well, but I hadn't thought about the inside, so a massive thank you for that.

That's something that needs to be investigated when the fuel tank arrives.

[Dyslexic Viking]

1 hour ago, jim89 said:

Is it necessarily going to be "that clean" though?

I'm wondering if there could be traces of lubricant from the pressing of the shaped "halves" that have also been (presumably) welded together?

Hopefully it's flushed with something at the factory to remove "bits" & the worst but whether that could be classed clean enough to paint straight onto ? I dunno...

Maybe flush the tank with petrol? That should remove any kind of lubricants if there is any I would think?

[Dyslexic Viking]

9 hours ago, hairnet said:

what later mercs does the tank fit

thats why they have them

Only fits Fintails as far as I know.

[jim89]

7 minutes ago, Dyslexic Viking said:

Maybe flush the tank with petrol? That should remove any kind of lubricants if there is any I would think?

I guess so yes.

Assuming yours has a leak on the horizontal seam, could it be corrosion has got at it from the outside in, rather than the inside out ?

Edit:- just read your post re painting & treating exterior! 😆

[Scruffy Bodger]

18 hours ago, Dyslexic Viking said:

New fuel tank was sent yesterday, can't get over that a regular car part site has a fuel tank for this one that's incredible. 

And looked more under the car and it's not leaking now that it's about half a tank so that's good, what's not good is that the entire rear underside of the car is covered in diesel and this has loosened the underseal and made a mess. I haven't quite figured out how to clean it yet, but I think it will be a lot of work. 

 

Diesel is a great rust preventer so I wouldn't worry about it too much. When I was a kid my old man ran end of life Mk2 Escort vans. He was given one as spares for another but as there was still MOT and tax on it he ran it for a bit. The passenger seat I was sat on was sat on blocks of wood and barely attached to the floor, I remember seeing the tarmac going by underneath where I was sat. The thing stank of diesel and had obviously had plenty of it spilt in the back over time, the rear bed was absolutely fine!

See also oily rag tractors or ones that have had diesel spilt and never cleaned off by the filler neck, the metal near there will be fine even if the mud guards have evaporated.