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Treating inside/outside of gas tank with POR15 products and removing evaporation tank

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Hello everyone!

I hope this article is informative to you. Please refrain from posts until I am done, approximately 10 posts.

The main reason for this project for myself was because:

1. Previous owner had replaced the 90 degree hose on top of the tank with non-fuel hose and it was rotted and leaking gasoline. This HAD to be fixed one way or another.

2. Gas tank was 35 years old and, although I have never had issues with rust in the fuel lines, I know if not treated, the tank on the outside and inside would eventually rust (further). I already knew the gas tank on the outside top was rusty.

3. I enjoy working on my Z and if I can make it stronger than original and keep it looking original, I will do that! This project I think accomplishes this, and also at the same time eliminates the evaporation tank, saving about 10 pounds. I am not going to say good/bad on the evap tank, all I know is that my fuel vapors are still being burned correctly and not entering the atmosphere. I will leave it at that. Coincidentally, if anyone needs a great shape Evap tank from a 10/71 I have one! I also have a bunch of the original hose clamps (I used good ol' American style ones--new).

4. Fuel sending unit was leaking a little fuel, and the gauge has always worked oddly, and since it's original I wanted to replace all items, including connection wires, rubber o-ring, retaining ring, and sending unit. My sending unit was jimmy rigged with the wires just twisted to the sending unit posts; I wasn't able to find any of the snapping connections, so I soldiered everthing together, and made some quick releases incorporated to make it better than new. NOT original, but better than new.

5. Learn something about POR15, because I've heard a lot about it, but have never used it and I wanted to see what it was all about. Hopefully some of my tips will help somebody out there. IT DEFINITELY IS THE REAL DEAL--THIS IS A GREAT COMPANY MAKING GREAT PRODUCTS. Get one of their sales magazines, they make some great stuff to keep our Zeds working and lasting!

Much thanks go to EScanlon and Beandip, both of which were instrumental in making this project become reality; if not for them, I would not have seen what POR15 could do and how it could help (in person).

First 2 pictures show the before and after pictures of tank and the hoses associated.

All pictures are 1024x768 reduced to under 300 kb.



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The next 5 pictures:

First 2 pictures were after I got my tank back from Beaverton Radiator after having it boiled.

I can't stress this enough--get your tank boiled before doing anything. I don't think my end results would be as good if I hadn't done this. My tank looked like crap before I had this done.

#1 thing I found out--the 'smell' inside the cabin wasn't from exhaust--it was from this stinky tank! Before I got it boiled, I HAD to roll my van's windows down--it stunk. After boiling, it had no smell.

As you can see in the pictures, it is pretty clean, but not perfect. This is where POR15 Marine Clean will come in handy, as it cleans very well.

Third picture are the strap bolts, there were in bad shape--all corroded, etc...here's a picture after I simply wire wheeled them with a shop pulley driven wire wheel. They look nice, and the nuts roll very smooth.

The fourth picture is of the ugly looking sending unit; I didn't keep any of the pictures, but the sending unit wiring inside that make it work, were very heavily worn. The fifth is the new OEM Nissan sending unit (with O ring and the new retaining ring) it was about $40.00 from MSA (www.zcarparts.com).






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The next 5 pictures:

The 1st picture shows the fuel hoses that I picked up from NAPA; 1/4 inch, 5/16 inch, and 5/8 inch. They didn't have the 5/8 inch in stock (not used much) but they got it from their warehouse the next day. Make sure you use fuel hoses, as heater hoses will be rotted eventually from gasoline. This was one of the reasons I did this project--the top 90 degree hose was leaking because it was heater hose the PO installed (can you say idiot?).

2nd picture shows how I had my car sitting during the work; jacked up the rear and placed ramps in place (you can't drive your car into this configuration). Make sure it's a sturdy situation, as you'll be under the rig; this setup was low enough that I could do some work through the hatch (as you have to do).

Third picture my first order from POR15--2 pints of 1) POR15 2) Chassis coat black...a big gallon of Metal Ready and a spray bottle (included free). The Chassis Coast Black supposedly matches the exact color needed to match old style frame color on American cars (good enough for me)...Since POR15 is UV sensitive, I wanted all the items exposed under the tank to be painted with a coating of Chassis Coat black (after the POR15). If it is exposed to light, POR15 will discolor with spotches of white (pardon, I guess like M. Jackson).

4th Picture is my second order, I wasn't at first going to coat the inside of the tank, but changed my mind, 2nd order is tank sealer, more Metal Ready, 2 quarts of Marine Clean, and a gas additive that is included for free.

5th picture shows a macro shot of how worn the pickup wires on the sending unit were....






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The next 4 pictures deal with cleaning the tank after getting it back from the radiator shop, having been boiled. The boiling cost I believe $80 and is well worth it. Gets 90% of grime off of it (inside and outside) and gets 100% of the nasty smell gone.

I decided to do the entire outside of the tank first because I wasn't sure if I wanted to do the inside--there was very little surface rust on the inside, but the outside had a lot of surface rust.

Everything coated with POR15 products are done in this order:

1. scrubbed with Marine Clean, let it soak, then rinse with water. Let it dry a little bit. Cleans all grime and oils and stuff off of the metal.

2. Apply Metal Ready and let it sit for a little while (no scrubbing), then rinse with water. Dry immediately. I did all this work on a very hot summer day so wetness wasn't a problem. Metal ready is an acid, it 'etches' the metal, giving it 'teeth' so the POR15 grips the metal better. GREAT stuff.

3. Once dry, apply POR15 like paint--its almost as thin as paint, a little bit thicker, and as it is exposed to air, it gets thicker and thicker--it will eventually be rock hard.

4. Apply chassis coat black like you would any paint--it is much thinner like paint as well. It is a rust inhibitor but not as good as POR15 (accord. to the company) so I never used only Chassis coat black but always painted it on top of POR15. **and I didn't coat everything with Chassis coat black, only items exposed and that could be seen--the only items I did this to were the tank straps and bottom of tank up to the middle seam.

1st picture shows mixing marine clean, about 20% Marine clean to 80% water and it's hot water from a tea kettle. (picture 2)

Picture 3 shows the scrubbing of the tank (with wire brush) and 4th picture shows the top half of tank done. Most of this project was done by doing half of the tank per activity.





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Ok, so now the outside of the tank has been scrubbed with marine clean, and all that extra crap on it is gone that the boiling didn't get rid of. The process was scrub with the 20% marine clean/hot tea kettle water using a metal 'tooth brush'....then rinsing with water and towel drying and letting it dry in the sun (it was a hot summer day in July when I did this)....

So now the tank is ready to be 'etched' by Metal Ready. This is a great product! It prepares the surface of the metal to be coated by POR15. Since POR15 is a very smooth coating, it needs some help adhearing to the surface...Metal Ready makes the surface uniformly rough and also 'eats away' the last bits of grime, etc. You can actually watch it working.

Pictures below:

First couple show what the tank looks like when you are spraying it with Metal Ready. When you buy a gallon, they give you a free spray bottle, so I guess plastic is immune to its acid effect. I did this first spraying on the grass--DON'T DO THIS! As you can see, it leaves a nice little circle of dead grass--it did grow back though. ***Also, unlike me, use some gloves!!! Since I was just using a spray bottle at this point, I didn't use any, but if you need to touch this stuff when its wet, treat it like its battery acid--because that is what its like.

I actually wire wheeled my tank straps (like I did the bolts for it) and I applied the metal ready to them as well. I had a large pad of 1/8 inch rubber and made some perfect templates for the rubber pads on the straps.

After spraying the metal ready, as long as you don't overspray it, its ready for POR15ing application--no need to rinse it in my opinion, but I think I did rinse it anyways....remember once one side is done, flip everything over and do the other side. After this step, we starting painting everything with POR15.






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The next picture:

Shows what I used to apply my POR15...I got creative with some disposable items that were cheap and relatively plentiful around my house.


Tuna Cans (or cat food cans)--have to be 100% dry--POR15 gets screwed up from moisture

Small plastic cups (like the kind that sesame seeds come in from a chinese restaurant)...these were used as a ladel from the POR15 paint can to the tuna can.

Plenty of Corn Dog sticks, 100% dry--to stir the por15 in the can before I scooped some out.

I bought 10 paint brushes and 10 pair of latex gloves along with my order of POR15--they sell good quality--I'd recommend their stuff.

Each 'episode' of POR15 painting, and I believe I had about 6 or 7 episodes, I used 1 tuna can, 1 plastic ladle cup, 1 corn dog stick, and 1 brush/pair of gloves.

Zip lock bags to seal up the POR15 can--so the lid doesn't permanently seal itself to the paint can.

I got 1 pint of POR15--I still have about 15% or so left in the can after my entire tank on the outside was done, so 1 pint is plenty for the gas tank job.

I CAN'T STRESS THIS ENOUGH--ALL PAINTING TOOLS HAVE TO BE 100% MOISTURE FREE. What makes POR15 such a great product is that it pulls moisture from the environment and hardens from moisture--which is unique to POR15 and why its a great rust treatment product. If one of my corn dog sticks or tuna cans would've had any moisture, I would've compromised the POR15 I was applying...


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The next 4 pictures:

1/2: That's me stirring and ladeling the POR15 into my tuna can for application to the tank straps.

3: Putting the lid back on the POR15 with a ziplock style baggy between lid and can--do this between each 'episode'.

4: me painting the straps--one side, dry, flip over...

****Don't do it this way--I thought at first putting these on zip lock bags when I painted them would work, but they glue right to them.

I went and wire wheel grinded off all the por15, hung the straps with baling wire from the garage roof (with paper on the floor) and painted them that way.

Remember, after the POR15 was done on each strap 100%, I went back and painted the side exposed with Chassis Coat Black, which doesn't discolor due to sunlight--doing the Chassis Coat black is the same exact process as applying POR15, but it is thinner, like normal paint, and doesn't start thickening as fast as POR15. Also, as you'll see in future pictures, POR15 is very very glossy--it doesn't quite look right--the chassis coat black matches what 50s hot rods had the frame painted from the factory--not flat black, just a little gloss in it--it looks just right.

POR15 likes to thicken real fast....that is why it is recommended to split up jobs into little 'episodes' with the little tuna cans and to buy a bunch of pints as opposed to getting a whole gallon of it--it will thicken over time no matter what you do once it is opened the first time. I would probably get pints even if I was spraying it on sections of the unibody, splitting it up into episodes. The stuff just thickens too quickly. I am happy to let you all know the ziplock bag between the lid/can works pretty good--my POR15 after 3 or so months is still liquidly feeling when I 'slightly' shake the can....Don't shake por15, always Stir it!!!!





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Next 3 pictures:

1. Shows first application of POR15 on the top side of the seam of the gas tank--just one good coat is all it takes.

2. Whole top of the tank done.

3. Shows the tank upside down, already 100% POR15'd, and a couple of days later, had painted the chassis coat black on the bottom from the seam up, and a couple of days later, here it is in the rain (good ol' Oregon in the Summer)....

As you can see, the top of the tank is super super shiny (that's the POR15) and the bottom is a little bit duller (and that's the Chassis Coat Black applied over a coating of POR15). So if I say I put Chassis Coat black on something, that section has a coating of POR15 under it by default. (in my applications of it).

Also note that my tank is dented right where the drain plug is--this came into play when I sealed the inside--I wasn't able to just take out the drain plug to drain it--it's pushed up too much--I had to drain from the fuel inlet hole.




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The next 5 pictures deal with sealing the inside of the tank:

1. to seal the sending unit hold, I just used the old sending unit with the old rubber o-ring and old retaining ring--can't beat this setup--also cut off the float piece.

2. to seal up all the inlet/outlets, I initially used ziplocks and tie-zips, and before I actually did it, thought about it, and thought they wouldn't seal too well...so I cut them off and used some rubber bands in place, which are 100% sealing--I forgot to take a picture of this setup though.

3. Stirring the POR15 tank sealer--this is really important, as the sealing paint was seperated (it had black / silver in it) and I had to mix it for about 5 minutes to get it all mixed up.

4. After pouring the entire can into the gas inlet, I sealed up the gas inlet with a ziplock bag and rubber band, and started shaking and shaking and shaking...notice my 4 year old son, Devin, the total poser.

5. More shaking and shaking and shaking. After about 10 minutes of shaking, I was ready to drain it all out--and because my drain hole was dented and not the lowest portion of the tank, I had to drain out of the fuel inlet and had to shake and move the tank many times to get it all out of there.

I must CAUTION you--this stuff is dangerous--I probably shouldn't have had my son near this stuff--you don't want some leaking on you when you're doing it--but I was pretty sure with my setup--huge rubber bands wound around a whole lotta times, that it was 100% sealed up--and it was. If it gets on you, it doesn't come off until your skins' oils take it off (like a whole week)...so be warned.






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Next 2 pictures show how most people would drain their tank, from the drain plug hole--and if you do this, make sure you wear gloves and wipe the threads before it solidifies---you don't want your threads with the POR15 stuff on it--but I couldn't do this because of the dents.

I had to move at many different angles (partly because of the baffles inside) the tank and drain it out of the fuel inlet--worked real good.

The third picture is taken looking into tank from sending unit hole looking at the small pool of sealant I couldn't get out (in like 20 minutes of draining time)...I just left it.

...and of good note--keeping all the inlet/outlets for the gas lines sealed up tight with ziplock bags and rubber bands did the trick--no sealant got in the lines to block them up--I did blow into them, but there wasn't any sealant left in the fuel lines.




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The next 5 pictures:

first 3 show how I sealed up the driver's side vent--this is the one that needs to be sealed when I remove the evaporation tank.

I used a threaded nut as seen in the picture, with the inner threads grinded out--it was just something in the junk drawer, and it fit perfect.

I used the 'quick setting' jb weld, hadn't tried it before, and I must say, it worked great--I'd recommend it.

3rd picture shows what the cap w/ jb weld looked like. Solid as a rock.

4th/5th pictures show what I did with the unibody right where the tank sits--I had 2 small surface rust spots on the spare tire well, so I por15'd those spots and then used some rubber undercoating to coat the rest of the area. I know some purists out there would say not to do this--my whole under area was rust free except for those 2 spots you see, so I didn't have any issues do this. I plan in the next decade to possibly rotissery the car and restore 100% so doing this now is just an ounce of prevention for a daily driver in the rain of Oregon....






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good job. Only one comment about the Metal Ready , it is ment to treat the metal and the rust if any is present . The surface must be clean of dirt and any grease or oil of any kind including droplets of sweat. no kidding . The metal ready will leave a slight residue behind on the rusted metal , this is after it is rinsed with water and left to dry . Do not remove this stuff , it is ok to apply the POR right over it. One more thing , The Mariene Clean is NOT just a cleaner like SIMPLE GREEN , or some simular product. Mariene Clean will etch also , and it is ment to be used with the Metal Ready. M. Clean is a great cleaner , however if you use it to prep any aluminum or mag wheels , take it from me it will take the shine off the surface and you will need to repolish. I found this out the hard way . LOL Great thread Gary :laugh:

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Yes, what beandip said....these are powerful chemicals!

Next 3 pictures:

First one shows my plastic piece on the filler next that mates the 90 degree hose to the filler neck hose piece. Most are cracked; mine wasn't, but I still swapped it with a copper pipe.

Next 2 pictures show how I did the sending unit--I didn't have the connectors, so I soldered the wires, put connectors on the end of the wires, and sealed it all up with liquid eletrical tape. I also used the rubber tubes that contract with heat to add further water resistance.




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Next 3 pictures:

Show the tank right before I put it back into the car. To eliminate the 90 degree bend on the top hose, I had my retired plumber dad solder me up a 90 degree copper pipe fitting as seen in the pictures.

Also seen is how the sending unit looks on the tank.




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Ok, we're down the home stretch!

I'm at the point where the tank goes back into the car, and the holes through the floor board in the rear that the fuel hoses went through need to be sealed up.

Some tips:

1. Be sure that you add the very top hose (emission hose) to the gas tank before you put it up into place....I put a brand new piece, a little long to make sure it wasn't too short--actually install it on the tank end for permanent installation, so you tighten the hose clamp all the way...leave the other end loose.

2. Since the 90 degree hose is loose on both ends, attach the gas tank end to the 90 degree copper fitting for permanent installation. Fish the other end through the hole in the floor board, and as you install the tank, have a buddy (that'd be my dad) pull the hose through the hole to take up slack. Probably other ways to do this, but found this worked great.

3. I found that adding the inlet/return fuel hoses (the ones that actual fuel go through to the motor) BEFORE you install the tank is the way to go. And I mean tighten down the hose clamps on the metal fuel lines end only (before putting the tank in place)...so you place your hoses on the metal lines and tighten the hose clamps, and as you can see in the pictures below, these were kind of a bitch to get to, to tighten the hose clamps you have just enough space to get to them at the corner back of the diff--the pictures show me using a screw driver in the optimum place.

4. The 3rd picture shows what I used to block all holes through the floor board that are left over after taking out the evap tank....I used rubber corks, and coated both surfaces prior to installation with 3m rubber gasket adhesive, let cure, and then coated both surfaces again and stuck them in. Had to experiment with the right sizes, don't recall what they were at this time, but measuring/eying the corks didn't really work--I think I had to go with the next larger size...if they're too big they don't even fit though.




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  • 2 weeks later...

The next pictures show:

1. How one of the corks look from inside the car (blocking one of the holes that the evap tank hose went through.

2/3. Not only did I use liquid electrical tape after soldering the wires of the sending unit together, I used the black rubber toobs that shrink when you light them.

4. shows how the wiring looks in the general area, note the male end snap connectors (which were shrink toobed as well, but I can disconnect if need be).

5. shows the tank straps completely done, and ready to go in....the longer one goes on the passenger side (the larger part of the tank side).






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Almost done.


1. show how the strap attached to the small adjusting bracket. Essentially you tighten the lower nut until tight, and then tighten the top on onto it to lock it in placed.

2. Shows how everything in the sending unit area looks when installed. Note the top hose, the strap arrangement, and how the wires looked. I couldn't get the shrink toobs to shrink as well as I'd like so I electrical tape sealed them up as well.

3. Shows the copper mating tube I used between the emission hose (the 90 degree bent tube) and the gas filler neck--I took out the plastic joint and put in a copper plumbing tube.

4. The FINAL PRODUCT! I felt like I just had a baby when I looked at this. Very proud. Now in a thousand years, the car will be gone, but the tank will be sitting there and nice and rust free looking!





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Well that's it. Some things I learned, and some rambling:

1. POR15 stuff is the real deal. This stuff is great.

2. All pictures were taken with a Canon SD500 Digital elph. Auto Focus, because I bought it for my girlfriend. 5 megapixels. Great Camera. Easily takes good pictures.

3. The sending unit is doomed to suck, as I found out a new one still has the same issues--goes up to 1/2 tank very quickly, sits there, and slowly goes to E....the wire piece on the sending unit is wound evenly through its motion, so I deduce that this is why this occurs...but I don't think I'll have to question its operation anymore.

4. Car runs great, no issues from my tank operations. Does need a new exhaust/brakes/tie rod ends replaced, but it runs great!

Please respond now if you'd like.

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  • 3 weeks later...
  • 2 weeks later...

As far as I've been told, I could have my wheels come off and have the tank scrape on the ground, and it isn't going to chip...rock chips definitely aren't going to have any effect on the tank. None whatsoever

I still have some bad door rubber, so a very little tiny bit of that...but redoing the tank didn't have any effect on the traditional exhaust fume problem. Just the stink of the tank is gone, which is completely unrelated.

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A question and my 2 cents:

Question: Did you have any problems with the fuel outlet pick up tube getting clogged by tank sealer?

2 cents: Great job on the whole article. Good pics, concise explanations. Thanks! One addition: MSA now sells fuel system grommet sets, so you don't necessarily have to go the 3M sealer route. I think it costs like $38


Thanks again!


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Had NO problems with clogs in the inlet/return fuel lines---they were completely sealed up on the outside of the tank with a zip-lock style bag with rubber bands, so I believe this had something to do with it....when I was done shaking the tank and draining out the inside sealer, I quickly blew into the tank to make sure they were clear (just with my mouth), and had no issues...when blowing in, it sounded like NONE of the sealer got into the pipes.

I think that this is because the return tube goes in at least 2 inches and that the pickup isn't exactly on the bottom (it's like .5" from the bottom) is why they don't get clogged...If you tried real hard deliberately, you might get them to clog up...

It was a pleasant surprise, because before I started this, this was my main concern...afterwards, I would say just do exactly as I did and don't worry about it because they didn't even come close to clogging.

Thanks for all the encouraging feedback. I am glad I was able to do this article...good way to try out my new digital camera as well...this article IMO was long long overdue, and now we can just point all questions to it...I tried to do it as a "Idiot's guide to sealing your tank with POR15" so I made it as simple as possible.

It really was a simple project, but very time consuming when you only have weekends, and a few hours on a couple of weeknights available. I was very 'anal' about making sure each process was 100% dry and clean and I didn't skimp in any area. I like to make sure I don't have to do anything for at least 10 years on any kind of project like this. I shouldn't have to do anything with my gas tank for a long long time.

I don't even know what those grommets from MSA are for....but the 3m sealer and rubber cork plugs cost about $5 total with lots of extras, so I wouldn't have done the $38 anyways. What are those for?

EDIT: I think I just figured out that those grommets are for sealing where the hose goes through the floor (seal the metal tube and the fuel hose)...good idea, but too expensive imo...much cheaper (and better imo) just to use some 3m adhesive...plus there's extra left over for any other household/zed project. 3m makes some good stuff.

You all have some good Holidays!

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Dave...I meant to "thank you" a couple of months ago when you first posted this "How to".So "Great Job". I am quite familiar with the application of the POR 15 products as I have done my Z inside and out with it(pics in my gallery). An experience not soon forgotten I might add.

The issue I have with my tank is how to fix some fairly sizable dents in the tank. Any ideas or experience on the repair of those first before using POR 15? I can have it repaired by a shop for $300.00 -$400.00 (boiled.dents fixed and painted). So that is an option. One I would prefer not doing if I could fix the dents... then use POR 15 to finish.


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