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  #16  
Old 11-18-2019, 01:12 AM
cmac2012's Avatar
Renaissances Dude
 
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I was thinking water and then the right type of mild acid solution. But you could be right - diesel might be plenty good. One appeal of water is I could train a jet through the sender opening, sort of a poor man's pressure washer.

I'll search the web to see what reports are available.

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  #17  
Old 11-18-2019, 05:22 AM
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lied to for years
 
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easy to make a better one,out of fiberglass.coat the old one with wax,brush on gel,then layer with glass matting.repeat at least 5 more times, let harden 2 nights. Cut fiberglass tank in half to to peel away from metal tank.Refiberglass the cut you made.2 more nights then mount. I made 2 250 gal diesel tanks for a boat I fished on.
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  #18  
Old 11-18-2019, 09:47 AM
t walgamuth's Avatar
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You really need to try the biocide Carl.
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..I also have a 427 Cobra replica with an aluminum chassis.
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  #19  
Old 11-18-2019, 09:49 AM
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Not a bad idea, in some ways, I'm in a weird place at the moment where I have so much work that buying a new one for just under $500 would take me less time that fabbing one in that manner. If it was an NLA item, that is an attractive idea. I worked at a fiberglass boat factory in my early 20s, I understand the principle but never thought about using the old tank as a plug. Also, one wonders if it would be just enough larger to be a PITA to refit.
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  #20  
Old 11-18-2019, 10:47 AM
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lied to for years
 
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most bike tanks are fiber,It would never rot again. Also there might be a overseas dealer of poly fuel tanks
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  #21  
Old 11-20-2019, 05:54 AM
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I bought the 1-13/16ths socket, was going to clean it while leaving it in but then I couldn't break the strainer nut loose. The ones I've seen in the vids had a 19mm bolt head welded on somehow because space is tight and now I get it. There isn't room for the socket, the 3/4 to 1/2 adapter, and the head of a socket wrench with the axle shaft in the way. I tried with a vice grips on the adapter, finally got it situated so I could really pull but just would not break free.

So I'm all Eff it, I spent the $40 on the socket, I want to see that strainer so I took the tank out. More thorough job anyway. Wasn't all that tough. The strainer looked remarkably clean.



That's just how it came out - the rusty bits on my finger are from swiping my finger just inside the hole, trying to show two things in one photo. Also much evidence of the same sort of rust seen in the primary filter on the nut on the hose connecting the strainer to the fuel line:



That didn't clean off all that well, looks to be rusted itself. I'll get a new one.

Looking through the sender hole one can see rust on the bottom of the tank but a seat of the pants examination of the outside of the tank indicates that it's far from seriously weakened. The metal thumps pretty solid.

I have an electric pressure washer, not nearly as strong as the gas powered varieties but it will put out some pressure. So far my searching indicates soap and water followed by an acid bath somewhat stronger that vinegar.

I see no swirl pot inside. I can see the hole where the strainer attaches, this looking through the sender hole. Nothing resembling that. My 325i has one. I might see if I can get a recommend on a service around here that would clean and then coat with some epoxy solution. The objection to an epoxy coating earlier involved a Bakelite coating on the swirl pot.
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Last edited by cmac2012; 11-20-2019 at 06:22 AM.
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  #22  
Old 11-20-2019, 11:54 AM
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Apologies, it looks like the w123 tanks didn't come with one. Good to know, because when they get dirty it makes for a pain to get clean.

You're free and clear to get a tank boiling and coating done if you wish. A radiator shop boiling will put those little biobastards into their hot chemical equivalent of hell
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  #23  
Old 11-20-2019, 12:56 PM
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No apology needed, that's good information to know.

Ooo, the hot chemical equivalent of hell. Sounds like the ticket.

Edit: crap, the radiator shop a good mechanic I know recommended can't do it for two weeks.

I found another place who can have it in a week, they recommended a new tank as they want $595. Pelican has a new one for $462, possibly free shipping, +tax about $500.
Might do it myself. I figure pressure wash, some kind of medium acid followed by baking soda fun, followed by more pressure washing. I have an old shop vac dedicated to wet vac, hasn't seen dust in ages, I'll run the exhaust port into that with my heat gun aimed at the vacuum intake, maybe 6 inches away. wouldn't want to melt the sucker.
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  #24  
Old 11-20-2019, 01:16 PM
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Found a good guide here:

How to: Clean Rust from a Fuel Tank (using Phosphoric Acid) - XJRider.com

I've restored four rusty fuel tanks, to date, and have honed a process which works quite well:

1. Drain the fuel tank and make sure all traces of gasoline (petrol) are out of it.

2. Remove the petcock and fuel cap.

3. Seal the petcock hole so the tank will hold liquid. I've found that a small piece of wood (about the thickness of a ruler) works well, held in place with the petcock screws.

4. Go to Wal Mart and buy a gallon of Castrol's Super Clean degreaser. Pour half of that gallon into the empty tank and let it sit for about an hour. This will clean out any gunked fuel and will allow the acid to dissolve the rust.

5. Rinse the tank and verify that any/all gunk is out of it. If there are still signs of stale fuel, pour in the second half of the Super Clean degreaser and repeat.

6. Rinse the tank again and ensure that all of the degreaser (and it's foam) are removed.

7. Go to Home Depot and buy a gallon of Phosphoric Acid. It's green and sells as metal Etch and Prep. You'll find it in their paint department. The phosphoric acid will remove any remaining fuel varnish and will also remove the rust inside the tank.
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  #25  
Old 11-20-2019, 01:23 PM
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A good used tank should be not too hard to locate. Whatever has happened to your tank was not that typical. As I thought about it. Someone may have removed and cleaned this tank before but used something like a strong acid. Somehow the protective layer on the steel the tank is fabricated with has gotten breeched. Or the steel the tank was made from had a very poor protective coating applied at the rolling factory.

You should have a pick and pull locally. As one option. I would do a quick cleaning and then an inspection of your old tank first. Five hundred when these tanks should almost still be a dime a dozen is somewhat strange.

Last edited by barry12345; 11-20-2019 at 01:39 PM.
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  #26  
Old 11-20-2019, 01:35 PM
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Post Rusty Fuel Tank Service

I've been tying to help you but you keep ignoring my advice on this...

It's a simple if laborious job .

Clean the tank well using the purple industrial de greasers sold every where, I like to toss in a hand full of sharp edged small flat washers, BB's or pea gravel, then fill it about 1/2 full of the de-greaser and water, button it up and shake the bejeebers out of it, remembering to invert it as lots of rust will be in the upper reaches of the tank .

Drain through a large funnel lined with felt and use the strained liquid to re wash it and get more crud out then rinse clean with water and re fill 1/2 way with a dilute mix of Phosphoric or Oxalic acid and water, the dilute mix should be one gallon acid to three gallons water, add the acid to the water, not the other way round for safety reasons .

Use the small sharp edged items with the de rusing agent too, it'll speed up the job and make it better .

Don't use vinegar it will cause flash rusting .

Phosphoric acid leaves a thin coating .

W123 tanks have NO COATING from the factory .

Phosphoric and Oxalic acids are sold cheaply in gallons at big box hardware stores, look in the flooring department .

Sometimes the self service yards don't punch holes in the fuel tanks, this means you get one for about $35 .

I bought the correct 21 gallon tank from a Mercedes Specific junk yard for $100 and was happy with that price, hardly anyone ever buys used fuel tanks .

If you buy a used tank, mind when they remove it as it's very easy to bend the neck when pulling it out .

Only the M-B original fuel tank filler neck grommet will resist Diesel fuel, all the others will dissolve in less than a year .

The in tank strainer is cheap from any junkyard, I'm sure you know there's an LKQ just down the road from you (South) they get lots f W123's in all the time .

The best filler cap gasket is blue, it's available from the M-B Classic Center along with the filler neck grommet and some 7MM fuel hose you'll want to replace at the same time , leading from the tan to the chassis .

Simply peel off the thin sheet metal crimped collar holding the old hose on and it'll pull right off revealing a standard hose barb .

Be sure to use the correct band typ of fuel hose clamp, a # 12 or 13 .

This is all do able easily at home, it sounds like you stumbled onto a jewel in the rough .

Biocide is important, you should use it periodically as a prophylactic measure, not wait for the clear plastic intake screen to clog .

Remember to order in a spare secondary spin on filter too .

In a pinch you can use the in tank screen from a gasser, it has finer mesh though .

I strain re re use the dilute acid mix for years ~ it's handy to de rust parts and hardwre, nothing alloy nor pot metal but all ferrous metals and brass / copper meaning it's handy for vintage carby jets and contacts from unobtanium switches....

Good luck with this, please keep us informed .

Craigslist usually had kids running impromptu junk yards out of their back yards, maybe look there to find the cheapest tank, it should come complete with sender, yours is going to need disassembly and cleaning anyway .
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  #27  
Old 11-20-2019, 01:39 PM
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Quote:
Originally Posted by barry12345 View Post
A good used tank should be not too hard to locate. Whatever has happened to your tank was not that typical.

You should have a pick and pull locally. As one option.
I'm running into the same thing with W123 that I did with BMW E30s. Wrecking yards always had them in the Oh-Ohs but now it's rare. There is a good looking '83 300cdt in Oakland. However, I just looked at their part price page and they include (may be punctured). I've seen that, they puncture them for quick draining. Have also seen it on oil pans, that a bit whack as removing the plug not tough.
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  #28  
Old 11-20-2019, 01:43 PM
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Quote:
Originally Posted by vwnate1 View Post
I've been tying to help you but you keep ignoring my advice on this...

It's a simple if laborious job...
Good advice! I'll study it.

I've read about the gravel idea elsewhere. I have some onhand that has the relatively sharp edges.
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  #29  
Old 11-20-2019, 01:57 PM
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I never realized that the 123 tanks where fabricated from uncoated steel. It seemed that Honda four wheeler tanks would so easily rust through from the inside years ago. I suspected almost no protective coating.


Early gas tanks seemed to be fabricated from hot dipped metal being applied. Then possibly electroplated coatings where used. Tern steel was the common term for the sheet steel gas tanks where made from.


I ran across GMs internal cost to make a fuel tank years ago. Possibly in the 1980s. It was about eight dollars in total. This would not include the gauge I imagine.


On a really old gas tank. Sometimes dried gas residue can resemble rust.
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  #30  
Old 11-20-2019, 03:30 PM
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Post Cruddy / Rusty Fuel Tanks

Because I work on a large percentage of older vehicles I have way more experience with cruddy and rusty tanks than I wish I did .

The shaking with 'scrapers' inside is really important ~ shake until your arms are falling off then shake some more, I like to shake side to side as well as rotate .

It's a simple if arduous task .

I do Motocycle tanks too .

I work on a tight budget so I've never tried "Evapo Rust" , many Mechanics and Motocycle restorers I know tell me it's the shiznit because it works so well and won't damage the exterior paint .

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