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My JB Weld fuel tank leak fix


antiextreme

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Finally getting my 620 on the road.  After a few test runs with a swapped head gasket and the new Weber I decided it was time to fill the tank, just to make sure I wasn't only sucking up the dregs from the bottom.  10 gallons later I parked it in the garage for the night.  Almost immediately I noticed a strong fuel smell.  I didn't see any puddling so I attributed it to the fact that I had just filled up and perhaps spilled some.  The smell was very apparent in the morning, so with a little more snooping around I saw that the bottom of the tank was damp and that the leak was coming from somewhere above the flange.  There was nothing to do but to drop the tank.  I decided that if I was able to locate the leak(s) then I would just JB Weld the spots.  If I couldn't find it, or the leak wasn't terribly obvious then I would use a tank liner kit, like Por 15.

 

First I needed to get the fuel out.  I had just filled up so I knew that I had roughly ten gallons in the tank, too much to catch in my oil change pan.  So I found a siphoning kit and went to work.  I grabbed two 5 gallon cans and a kit that worked marvelously.  It had a copper fitting at the end that self sealed to create the kind of pull needed to start the siphoning action.  This meant I didn't have to suck on the end to get it going.  Bonus!  Just insert the copper end and give it a couple shakes to get things going.  I was able to pull about 8 gallons out.  I positioned my jack on the other side of the truck and lifted it in the air to get all the fuel to the corner of the tank that I thought the hose end had likely settled.

 

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I was able to catch the remaining couple of gallons in my oil change pan, and then discarded it in an "environmentally safe" manner.  I'll leave it at that.

 

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Removed 6 12mm bolts on the tank hangers.  I used plenty of WD40.  

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No love from the car gods here.  Guess I didn't anoint the bolts with quite enough WD40.

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Disconnected all necessary hoses and tubes, including filler spout.

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This is what I ended up with.  It all dropped surprisingly easily, with limited amounts of grovelling and grunting.  Note how the previous owner had routed the vapor hose (?) and fuel return line.  Doesn't seem to be the preferred method.  This will be remedied upon installation.  I'm thinking this tank might have been from a different year truck because mine is a 74 and from what I understand they were not equipped with fuel return.

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I next cleaned and scrubbed and scraped.  I used a putty knife to hack off all of the caked on filth, and then a 4" grinder with wire cup brush to break through all of the flakes of rust and corrosion.  Then, with the outside of the tank clean and dry I poured about a half gallon of fuel into the tank and proceeded to slowly turn the tank over to reveal any problem spots.  I quickly revealed this happy little number...

 

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...and it's twin on the other side.

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Both sets of leaks were on the top side of the flange, directly behind where the tank is bolted to the mounting brackets.  This spot is prone to trapping moisture and other grime, which over time eats away at the wall of the tank.  Since I was able to find the leaks I decided to stick with my original plan and JB Weld the spots. For this I opted for JB Weld SteelStik. It is steel reinforced and formulated for rusty areas and fuel tanks. It was very easy to use and I am happy with the results.

 

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Since I had everything pretty well stripped down and cleaned I decided to throw a coat of primer on the tank and powdercoat the hangers in an effort to slow the corrosion, if not stop it altogether.

 

I think that this will yield good results.  I will let y'all know after I get everything put back together!

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Leaves, dirt and moisture collect there and rust is inevitable. I cleaned mine and sanded and ground it to shiny metal. Let sit in the sun for a day to evaporate any dampness inside. Used acid solder paste and tinned it with lead. Tin snips on an old rad tank for a small oval brass patch that I shaped for a snug curved fit. I tinned it also and heated and soldered it on. Surprise! the hot solder wicked in between the tank and the patch and gave me several years of dry running before I changed to a 4x4 long bed tank.

 

That JB is supposed to work ok on gas.

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10 gal is good for 250 miles there about. Larger tank is only good for traveling. My 620 had a 4" body lift and I lowered the tank mount on the frame. Was able to fit a 15 gal US long bed tank under the rear of the King Cab.

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I'm hoping against hope that it will withstand the test of time. However, I will say that further research indicates that I would be a total boob to not flush the tank and do a pour in liner since I have everything already removed. For that reason I have ordered POR-15 and will be applying it prior to installation. I think that will give me the best chance and greatest longevity.

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Before I install the tank I have a mind to use the vent on top for a return line. Any advice on running that would be appreciated. Is it wise to run rubber tubing all the way back, or is there a bendable hard line out there that I could use to run the length of the truck?

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The vent line is... a vent line. Evaporating gas has to get out to the charcoal canister for storage when vehicle not running. Better check, but likely the gas cap is one way and lets air in to replace the fuel as it is used. What happens on a hot weekend when the truck sits and the gas begins to pressurize the tank? Just sayin'. Maybe someone knows? Poke a hole in the gas cap?

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I have 3 ports on the tank. One is the supply line to the carburetor. The other two were actually connected together if you look at the photo above. There is a line coming from the filler tube right behind the gas cap that runs up to a vent line that then feeds into the carburetor. Not sure about the cap itself and how it is intended to vent. Just wondering if there would be any benefit to using one of the other ports from the tank to connect as a return line from the carburetor. That's all.

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Neither the intake nor the exhaust (late 70s California L20B?) are not native to the truck.  The Weber DGV carb isn't either.  Ditto gas tank and transmission.  For all I know the only thing legitimately 1974 left on my "1974" is the rust in the floorboards.  So, given that someone has Frankensteined much of this thing together I would just like to know that moving forward I am doing what needs to be done to make sure that this is going to run right, or as right as possible.  That's the only motivation behind contemplating a fuel return line.  

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What happens on a hot weekend when the truck sits and the gas begins to pressurize the tank? Just sayin'. Maybe someone knows? Poke a hole in the gas cap?

I've seen this many times.  The carb has a vent, so provided there isn't enough pressure to push fuel into the carb and make it overflow (uncommon) it'll just vent wherever it can.  Normally the gas cap seal is so bad it'll vent there.  The bigger issue is pulling a vacuum on the tank.  It'll boil your fuel (vacuum lowers the boiling point), collapse the tank, and stress the fuel pump until the motor starves for fuel.  Either situation will damage something in time, or leave you stranded.  Loosening/venting the gas cap will keep you running.  

 

You have no need for a fuel return line.  Even a basic aftermarket electric pump will handle the extra fuel without raising pressures.

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I've seen JB weld on a tank. It will seep though over time. It's a bit porous. It will stop the leak though.

 

I bought a motorcycle where someone used JB weld to fix a few pinholes... it didn't leak, but it was definitely not sealed either.

 

You Mileage May Vary. I hope it works! 

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I work at a dip shop where we strip paint, rust off car parts. I've dipped two fuel tanks of my own. Flushes old fuel, flushes dirt and whatever else is in there and kills the rust so it won't keep eating away at the steel ( which will make the JB leak). When it comes out the holes are welded up and pressure tested,and tank is good as new. This can cost over $200 when all is said and done. I always tell customers that tell me 'that costs to much', that if they are trying to restore a vehicle and want a original tank that has been restored that is just a cost associated with the project. If they just want a clean tank for less money that they should get a aftermarket tank. Sometimes they have so many hole they are just not worth the trouble of fixing.

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Now for the POR 15.  As I had previously noted I decided to go ahead and treat the interior of the tank.  This was my weapon of choice.

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I'm sure there are other products out there that will deliver similar results.  This is the first time that I had done this so I will offer any insights, tips, and pitfalls that I discovered along the way.  My kit came with what you see above.  Be sure to follow the instructions TO THE LETTER.  Plan on spending an entire day doing this.  I found that it was helpful to read all of the instructions ahead of time to make sure that I had everything lined out and wasn't having to scramble.  Also, there are a ton of videos on youtube that can help you prepare.

 

First, I decided to take stock of the condition of the inside of my tank.  Years worth of rust and corrosion greeted me.

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Per the instructions I rinsed out the inside of the tank with regular water.

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A little bit of swishing got rid of the biggest chunks of rust and debris floating around.

 

Next came prep for the cleaner/degreaser.  Per instructions, I duct taped all necessary opening.  Note that I used silicone plugs to stop up various tubes.  This worked well.  I made some alterations along the way with varying degrees of success, as you shall see.

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Equal parts degreaser and WARM water were mixed together.  

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Instructions point out that the water should not be too hot lest it melt the adhesive on the duct tape.  Now, you should consider beforehand from where you are going to get your supply of warm water.  Latter steps also require rinsing with warm water.  I was doing the work in my garage, unheated, in March, in Montana.  So, nothing was warm.  I brought in some buckets from the kitchen.  If your hot water heater is in the garage and it has a hose bib at the bottom you could probably tap into that.  If you decide to go this route then I would caution you to be sure that your hot water heater is clean before tapping onto that bib, as any contaminates from the heater will be flushed into your tank when you turn the valve.  Another option, which I wish I had thought of ahead of time was to buy a hose adapter for your kitchen sink and then run the hose outside and flush everything out there.  Oh well, hindsight's 20/20.  What I did worked well enough.  

 

I poured the solution into the fuel spout and then sealed it up.

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Now we begin to shake/roll the solution around inside the tank for the next 20 minutes.  About 5 minutes in you will be wondering what went wrong with your life that brought about such misery.  This is more physically taxing than you might think, but don't lose hope!  The results are worth the effort.

 

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There are several things I want to highlight about the above photo.  First are the couple of leaks that appeared after a short time.  I don't believe that either of these were due to a subpar tape job, rather they were brought about by the fact that the solution began to foam and bubble when agitated, thus expanding and building pressure within the tank.  Once the pressure was great enough to break the seals of the duct tape some small leaks started to appear.  I ended up re-taping the areas, but was unable to get a proper seal.  I eventually abandoned the tape altogether (as you will soon see) and was able to make the tank air tight.  Had I known ahead of time I would have pulled the silicone plug at the top of the photo to briefly relieve the pressure and thus not compromise the integrity of the tape.  For the next phase of the process I would utilize this technique with good success.

 

Tape 2.0, not much better; however, it sealed well enough to allow me to finish the cleaning session.

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After cleaning was completed I drained everything into a bucket.  This is the result, a murky coffee looking puddle.

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Now it is time for the metal prep.  I definitely didn't want this getting on the outside of the tank so I revisited all of my openings to assure that they were going to be tightly sealed and hold in all fluids.

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You can see that I abandoned the duct tape on both the filler tube inlet and the sending unit hole.  The sending unit hole was resealed by placing the rubber seal from the sending unit itself back in place around the mouth of the opening.  Then, I cut out a piece of cardboard that would fit over the hole opening.  I placed that inside a plastic sandwich bag and placed it on top of the seal, over the hole.  then I took the locking ring from the sending unit and used it to secure the bag with the cardboard inside over the top of the hole (see picture below).  This worked very well.  No leaks.  I wish I had done this for the degreaser/cleaner step as it would have worked well there too.  For the fuel spout opening I wrapped it with another plastic bag and sealed it with a hose clamp.  These both held tight for the next 20 minutes while I sloshed around the metal prep.  During this step I periodically relieved the internal pressure buildup by removing the silicone plug I used on one of the vent lines.

 

After 20 minutes I drug the tank into the kitchen for a thorough warm water rinsing, as seen below.  I notified the wife so that we could cordon off an area to do this.  She is very gracious.

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Now it was time to dry out the inside of the tank.  This may be the most important step.  THE INTERIOR OF THE TANK MUST BE BONE DRY!!  This step takes a while.  I first used my heat gun which worked very well.  Then I used my safe heater, which is little more than a plug in heat element.

 

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I also left the tank in the sun for most of the afternoon and blew it out repeatedly by using my compressor.  Make sure to periodically check every area of the tank to make sure there is no moisture hiding inside.  I achieved this by using a dental mirror and a flashlight.  I found that the hardest area to dry out was the seam line that runs around the entire interior of the tank.  Do whatever is necessary and use whatever time you need to make sure everything dries out.  Don't freak out if some "flash rust" develops as POR 15 is formulated to bond with some rust residue, but the quicker the tank can dry out the better for reducing the amount of flash rust that will tend to pop up.

 

I failed to take a picture of the interior of the tank after it was all cleaned and prepped!!! Just know that it was shiny and beautiful.

 

So now we come to the pour-in-liner.  Open the can and mix it to an even consistency and color.  Have a CLEAN funnel on hand to pour the mixture into the tank.  Also, not a bad idea to keep a damp cloth nearby to clean up any spill.

 

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Now pour the liquid liner in, seal everything back up, and SLOWLY turn the tank, allowing the liquid to evenly spread over every part.  Once you feel that this has been accomplished open the drain at the bottom to allow the excess to drain out.  

 

This is what the inside will look like.

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Using my flashlight and dental mirror I was carefully able to see that I had uniform covering everywhere.  Now, on my tank I had three ports: one was a fuel return line, one was a vent line, and the last was my fuel outlet.  This was not the original tank for the truck.  I have a vent line in the fuel spout that runs back to the intake and don't require a return line in a '74. I blocked off those two lines and only used the fuel outlet line, which is what you can see in the picture.  If you look really closely you will see something sticking out the end of the tube.  That is actually telephone line.  In order to make sure this tube was clear of any tank liner I fished a section of wire through until I could see it poke out the end and then withdrew it to clean out everything.  I'm glad I did as there was a small amount of liner that made its way into the tube.  If you decide to take this step be prepared to fish about 10" of wire through the tube (see below). 

 

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If you go up two pictures you can also see a good deal of liner puddled up at the bottom of the tank.  You want to do what you can to get this to drain out of the tank.  I gently tilted and turned the tank to make sure that all the excess found its way to the lowest part of the tank and escaped through the drain hole.  When I found the ideal position for maximum drainage I left the tank in place.

 

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And this is where it sits, propped up to cure for the next 4 days.  I have since removed the wire that is in the picture.  The drain plug remains out of the tank so that any residual liner can continue to drain until it is dry inside.  I will likely have to tap the threads to install the drain plug again as there will be paint built up around the hole.  

 

I am really happy with the results so far.  I will update again after I install and fill the tank!

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