I have a 300TD with an imploded fuel tank. I noticed it when I was replacing the sender unit. Is there a way to expand it to the original size? I'm going to give it a go, but just wanted to see if anyone else has tips on doing it.

Thanks.

industrial magnets, a come along and a bucket of holy water.

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Air pressure.

Don't forget the earplugs and a blast shield.

3 psi should be all at most

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1981 300SD 512k OM603

I agree with air presure. You have checked the tank vent. Had to be the cause of the problem originally.

ditto

just thought the magnets would be more fun

dou you plan on pressurizing w/o removing the lines / tank?

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I wouldn't.

This definitely seems like a "drop the tank" job to me. Especially since the vent (obviously) needs repair.

Just seems like you'd be a lot better able to access and seal every inlet/outlet a lot better and way easier with it out on the ground. But I've never actually done it, so what do I know?

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Seems like a lot of hassle-a tank at salavage yard is less then $50 here in Florida

I'm guessing vacuum collapsed it, so the opposite (pressure) should expand it. Be sure to disconnect both fuel lines.

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K

You did not say how bad it was if it is only a little bit puckered and dose not interfere with the tank sending unit I would just leave it (after cleaning out the tank vent). You will just need to learn from experience how much you tank now holds.
Air pressure can be dangerous and you may end up with a puffy tank that still has dents in it. I also think that if you are going to use air it would work better if it was air over hydraulic; meaning that you fill the tank mostly with water before you apply the air pressure (you will need an air pressure regulator if your compressor dose not have one and start at a low pressure and work up slowly).
Another way if you have the equipment is to use one of those stud welders that the body shops use to weld the little studs to sheet metal to pull out dents. You attatch a slid hammer to the stud to pull the dent. But not doubt that that a used tank is easier and cheaper.

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84 300D, 82 Volvo 244Gl Diesel

In the TD its more likely somebody bottomed out the back end since the tank is outside the body and not as protected as the sedan.

I guess I should add it depends how much it has imploded. Usually if not too bad the weaker areas design wise like the flat areas are the first to reduce. So the air pressure will deal with them first.

A good air regulator should be employed as it will not take too much pressure to undo the problem I believe. Well worth attempting in my opinion. The rolling seam welds used to construct tanks are pretty strong. It is not a case where you are going to blow the tank apart unless uncontrolled high air pressure is introduced. It probably takes in excess of fifty pounds pressure to actually rupture the tank metal.

Most likely any lesser presure would just expand the tank well beyond its former capacity. You do want to visually inspect the tank as you are inflating it back to size. That way you cannot overexpand it nor leave it under expanded . So removal from the car is prefferable. Good time to clean your filter in the tank and clean the tank out in general if it is dirty inside. Let us know how you do.

If you feel insecure about this. The poster mentioning to fill it with water first. That eliminates any hazzard iin a reasonable easy fashion. You have nothing to lose by trying it. It should come out fine. Just by slowly increasing the pressure and keeing an eye on it.

The upside besides being cheap to do is you know your old tank was not putting dirt out into your fuel system. Or rust from the internal coating usually lead and a mix of other metals breaking down.

Tanks are manufactured from steel with a coating of primarily lead and a mix of other metals on both sides. Thats why when you see a tank under a car it is not rusty until the coating has deteriorated with quite a bit of time.

The downside was since the 1950s the coating has been thinned way down. Also the amount of lead in the metal mix is less. Originally it might have been close to one hundred percent lead. The coating was so heavy in the thirties it is still not unusual to find a tank from that period with no obvious rust. Tern steel was either the product used to make all tanks from in north america or the bulk of them.

I may not have the spelling of the word tern right and it may just have been the location of the specialty mill that produced the sheet product. The stamping of the tank halves were done elsewhere. Then joined with a rolling arc welder. Two wheels compress the halves together in the seam area and provide the current to weld the metal together while traveling at the same time. Just kind of like a sewing machine.

I do know perhaps a little more than the average guy about automotive gas tanks. Not much mind you. We did produce in this province at one time about seventy five percent of the aftermarket gas tanks you see around.

Started production in 1980 basically. It was so profitable the two separate operations were purchased and moved to Montreal, Quebec. The amalgamated company is known as spectra premium gas tanks. You might just see one of their fleet of trucks on the highway delivering a load if you live in a rustbelt area.

The reason I suggested filling the tank with water is that because air compresses it is kind of "springy" and by leaving only a small pocket of air in the fuel tank you reduce the springy area with the liquid pushing pushing outwards more evenly to make expanding the tank more controlable.
I was also thinking that if the tank was filled with water the job could be done with an electric tire inflation type compressor that can be bought in the $20-$30 range powered by your battery. Most of them go up to 210-220 psi but put out a small volume of air that pressure could be easily controled.

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84 300D, 82 Volvo 244Gl Diesel

Okay I now understand where you were coming from. I considered the water as the absolute safety item. If a tank were to rupture the pressure is basically instantly relieved. You may get a little wet from the small pocket of compressed air expanding in there. Water basically cannot be compressed or reduced in volume. Therefore for practical purposes it cannot expand like compressed air will during release from an enclosure.