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So I recently purchased a second 240z. This one is a 10/71 car and has been sitting in a barn for the last "8 years" previous owner claims less but the tag says 2009. Either way I drained the gas out of it today ~ 6 gallons of it. It came out really orange, rusty color. What are my options here? Can I just run some cleaner through the tank or do I need to seal it?

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I bought one that had been sitting with fuel that came out orange and smelt horrible, varnish I've heard it described.  I put a Fram g2 clear plastic filter coming out of the tank and drove it half way around the block and walked home.  Clogged it up pretty quick.  Dropped the tank and cleaned it with muriatic acid then coated with Red-Kote liner.  Replaced all the vent hoses too.  Took my time and let the liner cure for a week before putting it all back together.  Zero problems so far, did this about two years ago.  I have a glass filter before the mechanical fuel pump and it has never been anything but clear or fuel color.  :)


Inside tank crud, not rust, it wouldn't stick to a magnet.




After acid wash,




After lining,


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siteunseen, what did you do about the internal lines to the tank? I would think that it would get clogged with the coating. It seems that the fuel tank was really clean after cleaning with the acid wash.


I am leaning more towards just cleaning and leaving it as is. There was no coating on the inside of the tank from factory so assuming you clean out the rust there should be no more problems???  Looks like you had a pretty nasty case of crud in tank, i don't think mine is that bad, while the fuel came out orange there was no crud that came out with it or bits of metal. 

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I've heard that after washing with acid, the freshly etched metal will rust easily. Using phosphoric acid will leave a coating (because it converts the rust) that will help prevent flash rusting, but if it were my tank I would still spend the 30 bucks on red kote.


I've also heard of a number of ways to do this btw. Muriatic, phosphoric, hydrochloric acids, white vinegar, even molasses. I'm planning to use phosphoric then coating, on mine, but still doing plenty of research to make sure that's the right decision.

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Im also curious what people have been doing. I pulled mine to clean it as it sat for almost 30 years. I rinsed it out and took the waste wash water for proper disposal and thats as far as i got. Mine looked similar to siteunseen's pictures. I strongly recommend being as careful as possible. I spilled some and i could smell it in my yard for weeks.


I may have to expand my searches to online. I priced some out local to me in Canada, and most cost the same as a fuel cell which seems to defeat the whole point if i can get a new fuel cell for less than repairing my stock one.

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Here's what I remember right off.  I'm sure I'll forget something so ask anything you're not sure of.  I coated my 280s tank first, no idea what I was doing.  The 240 tank was much easier.  Baking soda and water mixed will neutralize the acid, no flash rust for me.  it's a quick and time sensitive process so read a few times then write out a plan.  have everything close by and ready to grab.  A leaf blower in the filler hole for 10 minutes will dry it out after the soda and water wash then acetone and before the Red-Kote lining.  I bought a rubber cap for closing off the filler hole, you'll be using it for the acid and baking soda and water then the liner.  Tape off the vent lines, I used Gorilla tape.


You'll need about 4 five gallon buckets. 1st for pouring the dirty acid in, 2nd for baking soda and water premixed-reuse this one, 3rd for draining the excess Red-Kote into, 4th to sit on until you need it for something.


My "steps".  Wear rubber gloves and don't breathe the acid's fumes, fans are nice to have blowing the air around.  A respirator or just stay away from the fumes.

First take the tank to a spray car wash and blow the inside out as best you can, then clean the outside.

Second, cover all the holes but the filler hole.  Have the rubber cap ready for that hole.

Third, pour a gallon of muratic acid in.  Slosh it for 5 minutes, maybe a little longer if it's bad.  carefully remove the rubber cap, it'll blow off in your face from the acid building up pressure, make sure it's tight while you're sloshing.  Pour that nasty stuff in an empty 5 gal. bucket, put it outside.  I killed ant beds with mine, scorched earth., 

Fourth, pour in the pre mixed soda and water.  I did this in two rinses, first was a pound box of soda and one gallon of water, next 2 gallons of water with a pound of soda.  pour this back in the bucket and put it outside.

Fifth, pour in a quart of acetone to evaporate any water, slosh that around then drain out and put a leaf blower in the filler hole for about 10 minutes.  Make absolutely sure it's dry before you put the Red Kote in.

Sixth, pour in a quart of liner.  Slowly rotate the tank all around covering every part.  Then remove the rubber cap and stand the tank up on a empty five and let it drain.  You should have a half of a pint left over, just chunk it.  Remove the tape off the vent lines and blow them open with your breathe while it's draining.  If you let one get too thick use about 30psi of your air compressor to blow through, DON'T hit it with 120psi ( ask me how I know).

Lastly, put the tank in the sunshine until dark then slide it under your car for at least a week.


If you read these two things you can do this.  Study what you need to do and write it down in order, have that sitting on your workbench to look at real quick.




http://www.damonq.com/techsheets/red-kote.pdf,  Red Kote's site is down right now but this is a link to their instructions.


Get a funnel and cut about half the drain spout off to make pouring stuff in the tank easier.  Here's the rubber cap for the filler hole, the big one.

3e25856a-bd25-4192-b561-4dbc20c5be68_100I Already remember something I forgot.  I bought a new sending unit and O ring from Nissan so I pulled the old cruddy one out and cut all that float mess off so I could use the head of the sending unit to plug that big hole.

Edited by siteunseen
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I am leaning more towards just cleaning and leaving it as is. There was no coating on the inside of the tank from factory so assuming you clean out the rust there should be no more problems???  Looks like you had a pretty nasty case of crud in tank,

I believe someone's kid put a bucket or two of dirt down that big ole filler hole. :lol:  


My thinking on the lining was it can't hurt if done right and ALL newer cars have a lining.  I drive mine on weekends and so sometimes it may not move for a couple of months.  If the tank isn't full of fuel there's a chance rust could form from moisture created by the ethanol (ethyl alcohol) which attracts and absorbs water.

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Hi guys. In all these years of dragging old cars out of everywhere we usually clean the tanks with laquer thinner and a 2 ft or so piece of chain. Let it soak and slosh the chain around to loosen rust and varnish. I did this a few times on my '61 VW tank while building it. Then sealed it with Red Kote.

Take your time and don't rush. This has always worked well.

To clean the hard line I've used and old clutch cable, PB Blaster and laquer thinner. That was on the '61 VW. Not sure if you could do that part to a Z car.

Good luck!

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Hi guys, thanks for the input, really sounds like red coat is the way to go. I'm just not sure what to do with all the chemicals as you are finished using them. I still haven't figured out what to do with the old gas. The local collection agency hasn't announced the pick up times for this year yet. I live in city limits, so i don't just have a place where i can dump it. So i can't even think of a good place to get rid of that much acid or acetone. 

Plus i have tried to use the POR15 tank sealer before and failed miserably, my guess is that I didn't wait long enough to for the tank to dry. But i did have two heatguns in it for 2 hours on high so i figured it would have done the job. Anyway i ruined a 240 tank that way and I'm not looking to do that again. I think there is a renu place here close to me. I guess i'll see what they charge and if it's reasonable i'll just let them handle it. 

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Good info here.  My 70' 240 tank  has sat since 1990 out in a field.  I'm sure it's filled with sand if not rusted.  There's no holes that I can see, but I'm certainly going to drop it for a look before trying to put anything in it. I've used phosphoric acid for rust before, and I'm going to use a lot of it for the body.   that redkote sounds like it should be a standard procedure. I'm going to try what you've posted here and I'll let you all know how it works out.  Likely this weekend I'll drop the tank.


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