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I am planning to move the filler connection on my 3A  fuel tank so that it lines up with the filler cap. I will cut out a 6"x4" plate with the inlet on it and then weld it back in the best position. The fuel tank is dangerous and my plan is  :-

  1. Wash it out with warm soapy water
  2. Rinse it with clean water
  3. Allow diesel exhaust fumes from the Passat to fill the tank for 15 minutes.
  4. Cut out the panel with my disc cutter.

Is there any advice on the forum which could help ?  It is not worth risking any damage to the tank or myself.

Thanks Richard & B

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I imagine what you are proposing will work. When I repaired my tank, I blew it out with an airline before cutting out the rusty portion with a monodex cutter using plenty of lubrication. That way I avoided any sparks. 

Rgds Ian

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Thanks for the help. So far I have been advised by the welding company but I am keen for any other help. I am planning to use my regular disc cutter and I understand that the content of the exhaust fumes , carbon monoxide, will neutralise the tank.

Any one else had success with the petrol tank ?

Richard & B.

 

Edited by Richardtr3a
adding carbon monoxide
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Why not get the right tank first as last Richard, a lot safer and theres no possibility of any debris being left in the tank.

Stuart.

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Richard - following on from Stuart’s post, for £250 fora brand new top quality alloy one, is it worth all the hassle with the old one?

If you successfully weld in a new patch, you will inevitably get internal corrosion around the weld seam which will then be exacerbated by the higher ethanol content of modern fuels
 

If however you are going down this route because you have a non standard alignment of the mountings and inlets and outlets holes in your body, then fair enough

cheers

Rich

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Fuel tanks can certainly be dangerous, but a good reasoned approach to clearing out fuel vapors will make the operation safe.

I'd skip the exhaust gas step. Its unecessary. (And carbon monoxide is flammable, by the way). MIG shield gas would be a better choice, but still unnecessary.

Ed

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When the old boy in the local garage soldered a patch on a tank for me he rigged an air line to blow through the tank while he worked, I suppose it puts a slight positive pressure on the tank? Anyway it worked for him and he still has his eyebrows 

George 

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I needed to have an alloy tank welded, which I can't do myself.   Local firm cautious, so I washed the tank out, repeatedly.   Left it overnight filled with hot water and detergent (Flash floor cleaner), repeated morning and night.    After a week, it had NO fuel smell, the welder was happy, and the seep is cured.

John

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Very hot soapy water will dissolve most hydrocarbons. Do it a couple of times (be careful when hot).  If you can make 100 degrees C steam (Wall paper stripper) and purge the tank that’s even better. steam if the surface is very rusty and also the seams can “store” HC’s and release them when becoming hot. 

Waldi

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Thanks to all for the advice. I have two tanks. 1x central outlet &1x outlet on the edge. Neither have the inlet connector in alignment with the filler cap.  It has a bent rubber hose for many years so I am not in a hurry. I will contact the welding company before the week end. Thanks Richard & B.

Edited by Richardtr3a
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Hi richard just re read  this thread, I thought you were planning to weld the tank yourself, now

you mention a welding company.

If you are not doing teh work yourself, take it to an independent radiator repair firm, they will steam the tank, and resolder the neck.

They will have done this many times, and there should be no issues.

John.

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I met a guy through work years ago who was a mechanic (a dim one). He was asked to repair a petrol tank while working in a pit.

Let's just say the repair didn't end well despite precautions and he now has nothing to keep his glasses in place or keep his head warm in winter.

For me if a tank needs welding or repair its probably best to replace with a new item as its likely not going to be lasting long. Just my opinion but after seeing him it seems more sensible!

Andy  

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          I have successfully repaired several petrol tanks with a mig welder. Make sure the tank is well flushed out to remove any petrol smells, then fill with CO2 from the welder and weld the tank. Finally clean out the tank and use a fuel tank sealant to protect against rust, ethanol and seal any pin holes.

          Cheers Richard

 

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If you are concerned you could fill the tank with water and only leave the area to be welded dry. This minimizes the effect should something go wrong. But cleaning remains equally important.

Waldi

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Yesterday I removed the petrol tank from the car.  I washed it out and connected my diesel exhaust to the inlet and ran the engine for 25 minutes. The other openings were all blanked off with tape except the fuel pipe connector and the exhaust fumes cleaned out the tank. 

I tried a long bamboo pole with a couple of matches on the end. There were lit and offered up to the tank from around a corner of the garage. There was no reaction.

So I measured up the inlet tube position and cut it out with a small plate still attached. I offered the plate up to the tank back in position in the car, and while it was lined up absolutely, I made some guidelines on the two surfaces so that the welder can position it correctly in the workshop. I also fixed two sides of the plate in position with gaffer tape.

It is now with the welder who will be able to weld two sides of the square and then remove the tape and make good all round. I am hoping that the heat will not interfere with the original brazing . He is making some very precise parts in very careful detail, for a commercial pumping operation in the USA.  So at this stage I am very confident that it will fit. ( Wait and see )

Last time I fitted the tank , I sealed it with a tank sealer called  Slosh, which I can not find. Please recommend a quality sealer which I can use before I refit it next week.

Thanks Richard & B.

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Richard - I love the description of your (non)explosion test, made me smile!  Had it exploded, what would the neighbours have thought?  As you have the tank out and clean, I would advise the use of a Slosh sealant - I described how I did it (see Technicalities CD, Section K3).

I used the Moss Slosh Tank Sealant in 1997 - I gather there is now a 3-part treatment.  Nevertheless, after 23 years it is still OK.

Ian Cornish

Edited by ianc
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15 hours ago, Richardtr3a said:

Last time I fitted the tank , I sealed it with a tank sealer called  Slosh, which I can not find. Please recommend a quality sealer which I can use before I refit it next week.

A word of caution. Mark Mason, who restored KST 277 in 1994, told me he opted for using Slosh. When he reached the stage of running the engine, much to his surprise, the newly applied product began to slosh up the fuel line too.

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1 hour ago, ianc said:

Richard - I love the description of your (non)explosion test, made me smile!  Had it exploded, what would the neighbours have thought?  As you have the tank out and clean, I would advise the use of a Slosh sealant - I described how I did it (see Technicalities CD, Section K3).

I used the Moss Slosh Tank Sealant in 1997 - I gather there is now a 3-part treatment.  Nevertheless, after 23 years it is still OK.

Ian Cornish

image.thumb.png.d243c63060f0acdfba70d389878bed20.png

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David - Perhaps Mark did not allow sufficient time for the Slosh to cure fully.  I recall that I carried out the work in the August of 1997 and it was decidedly hot weather.  Hard work for a small person (less than 10 stone) shaking an oversize (18 gallon) tank about with stones inside to dislodge loose material from its walls.  Preparation is very important - I can't remember what the can said about curing time, but it would have been a few days before I got the tank re-installed and was able to put fuel inside.

Some metal residue did get carried from the inside of the fuel pipe to the filter bowl over the next few weeks, but I just cleaned the bowl periodically and nowadays I just have a look when I hand prime before starting the engine.

Ian Cornish

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1 hour ago, ianc said:

Some metal residue did get carried from the inside of the fuel pipe to the filter bowl over the next few weeks, but I just cleaned the bowl periodically and nowadays I just have a look when I hand prime before starting the engine.

+1 Good point Ian :)

The 3 has only done 15,500 miles since! It was delivered to the Port of Dublin and when, long last, I started to drive, after filling up the 2 thirds empty tank, I only did about 1 km before it kept cutting out. The glass fuel filter under the tank was chokka with black gunk!

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On 8/15/2020 at 9:01 AM, ianc said:

Richard - I love the description of your (non)explosion test, made me smile!  Had it exploded, what would the neighbours have thought?  As you have the tank out and clean, I would advise the use of a Slosh sealant - I described how I did it (see Technicalities CD, Section K3).

I used the Moss Slosh Tank Sealant in 1997 - I gather there is now a 3-part treatment.  Nevertheless, after 23 years it is still OK.

Ian Cornish

Hi Ian, 

 The neighbours were out and some of their friends were waiting at the gate. No explosions no problems.

My tank was Slosh sealed in 1986 and has not caused any problems since. How can I seal the new weld only around the inlet . There will not be pinholes but future rust will find a home. So I need some small quantity of tank sealer and leave it upside down until it cures. What can I use ?

Richard & B.

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On 8/16/2020 at 5:43 AM, Richardtr3a said:

Hi Ian, 

 The neighbours were out and some of their friends were waiting at the gate. No explosions no problems.

My tank was Slosh sealed in 1986 and has not caused any problems since. How can I seal the new weld only around the inlet . There will not be pinholes but future rust will find a home. So I need some small quantity of tank sealer and leave it upside down until it cures. What can I use ?

Richard & B.

Sealants aren't necessarily patchable. Also, the heat damaged area of the sealant probably should be removed.

It's one of the downsides of tank sealants--after they are applied, future options for tank repair are limited.

Ed

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The tank is back from the workshop, and the welding is very neat. I tried to  fit and see how it lines up now, and it is in a perfect position. There is some bare metal where they have welded and I can repaint the outside but how can I deal with the inside. I have two mirrors on long handles and neither will fit in the tank.  I use a Hammerite product , Kurust   , and I treat all parts of the car with it. It leaves a black coat and is very efficient.

I am thinking of pouring the rest of my bottle into the upside down tank with the inlet and vent sealed with tape. This part of the tank never has fuel on it so it might help with rust proofing. My question is will it damage the old  Slosh tank sealer on that surface ? I was thinking of a brush with a modified handle but it would be difficult to be sure of covering all the new weld inside. I am also looking for new batteries for the torch to help with inside inspection.

Thanks for any help, 

 Richard & B.

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