OT Fixing a Plastic Gas Tank.
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  1. #1
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    Default OT Fixing a Plastic Gas Tank.

    I've got a 2002 Chevy Astro van with a leaking plastic gas tank. From my searching on the web I've got about as good of chance of finding one as I have of getting a booty call from Valerie Bertinelli. I did find a used one in a wrecking yard. The only problem is that has a ragged 3/4" hole in the bottom where the yard drained the gas. You can buy kits to patch plastic gas tanks, however there more for patching a crack or small hole than a 3/4' hole.

    My plan is to make the hole round and turn a plastic plug to fit. I will then use some of the magic goo in the repair kit to glue in place. After it sets up solid I will file it down to match external contour of the tank, then use more magic goo and the fiberglass cloth that came in the kit to put about a 4" X 4" patch over the plug.

    Does it sound like it will work and last a couple of years until I can get another vehicle?

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    Yes, it sounds as good a plan as any. You can have Valerie all you want, just keep your hands off Jennifer Aniston as she will be returning my calls any day now.

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    There is one on Ebay, used, for $275.

    Another thought would be to use a rubber expanding freeze plug...then glop it over. I'd almost bet the rubber would seal pretty well without and glop, if you could get it to register properly in the hole.

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    Repair will not hold, get a new one or used...or whatever.

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    Quote Originally Posted by plastikdreams View Post
    Repair will not hold, get a new one or used...or whatever.
    Why won't it hold?

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    Quote Originally Posted by SIP6A View Post
    Does it sound like it will work and last a couple of years until I can get another vehicle?
    Depends on the kind of plastic it is. If it's polypropylene (a likely choice), glues will not stick.

    It may be possible to fusion weld it. Trying to use an open flame for this may become exciting.

    Someone may have experience.


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    Cut out maybe a 2" hole. Drill four smaller bolt holes. Cut out a U shaped nut plate to fish up through the hole, and cut a mating plate for the bottom to bolt through. A little bit of compatible gasket material and you are good to go, assuming the area with the hole is flat. It's not too hard to form for a noncompound curve either though.

    Or you can keep it small and use an electrical knockout seal with the little wing nut things and some added gasket.

    Honestly even some coarse thread self tapping screws would work, but aren't my favorite.

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    Quote Originally Posted by SIP6A View Post
    Why won't it hold?
    My dad used to have a shop, mostly auto hvac repair and wholesale but he would do gas tanks as well. Anytime a customer came with a hole or whatever in a plastic tank he wouldn't do repairs as they never lasted long and were a liability. I once put a small nick in the very top of a BMW gas tank doing an audio system and BMW said any repair would void the warranty. I guess there's no real surefire way to fix the plastic in the solvent environment of gasoline.

    Metal tanks he just soldered up and that was that.

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    The only way I would trust a fix like this, would be to make a plug with an o-ring sealing surface. I have tried to fix tanks before with magic goo and it just leaves to headaches.

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    Quote Originally Posted by Joe Gwinn View Post
    Depends on the kind of plastic it is. If it's polypropylene (a likely choice), glues will not stick
    It's high - Density Polyethylene (HDPE)

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    Where is the leak on current tank? If just a crack I would think it would be easier to fix than a hole. If it leaks what does it drip onto? Leaky gas tank is always sketchy.

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    Use the old plastic one as a template and make a new one from sheet metal. If your welding skills are not good enough to seal the seams take it to a professional.

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    Quote Originally Posted by SIP6A View Post


    It's high - Density Polyethylene (HDPE)

    There should be a recycling symbol on it somewhere that will tell you the material. A hot air welder should be able to fix it if you can get some compatible plastic for the patch. I’ve repaired a lot of various plastic items using one, and a soldering iron and flat tip before I had the air gun.

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    Look on car-part.com

    It's the web site where salvage yards list their parts for sale. Looks like 16 within an hour drive from you for between $50 and $75. Can't imagine they would sell them with a hole in it but easy enough to ask.

    Check and see what year range that tank was used. If, for example, it's 2002 to 2011 you can look for a newer one.

    Steve

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    Quote Originally Posted by SteveF View Post
    Look on car-part.com

    It's the web site where salvage yards list their parts for sale. Looks like 16 within an hour drive from you for between $50 and $75. Can't imagine they would sell them with a hole in it but easy enough to ask.

    Check and see what year range that tank was used. If, for example, it's 2002 to 2011 you can look for a newer one.

    Steve
    Thanks Steve. I will get on the phone Monday morning and see If I can find one hole free. The one I'm talking about fixing is from an auto salvage yard. I was told the ones in parts yards all have holes in them. Will do some checking.

    There is two year ranges for Chevy Astro vans 1985 - 1994 and 1995 - 2005 any one from the 1995 - 2005 run should work.

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    Plastic piping for natural gas gets fittings welded on, so a similar process ought to work. On gas piping, the fitting to go on has the pipe contour. A heated plate is sandwiched between the fitting and the pipe, and when both surfaces are melted the heater plate is slid out and the two parts marry. An interesting facet when I first learned about it, was that they can add branches without de-pressurizing the line. Weld the valve and fitting, then perforate the main line.

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    Any patch using rubber or O-ring needs to be neoprene if it's exposed to gasoline.

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    Quote Originally Posted by Blazemaster View Post
    The only way I would trust a fix like this, would be to make a plug with an o-ring sealing surface. I have tried to fix tanks before with magic goo and it just leaves to headaches.
    Agree.

    If you must fix it rather than get a replacement, I'd use an o-ring mechanically compressed between an exterior flat, say 2" diameter, cap made of 3/16" material with a 6 or 8 hole bolt circle for the outside. Cut a circular groove to receive and trap a thick o-ring. For the inside use a split ring of maybe 3/16" (might get by with 1/8") steel drilled and tapped with a corresponding pattern. Fish the split ring inside. Place the cap and run up SHCS screws to draw the cap and ring up snug to the outside of the tank. If you don't trust the o-ring fully, put a bead of silicone rubber on the cap before you draw up the ring.

    OP, I like the new tank better, but that is not the question you asked.

    Denis

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    Quote Originally Posted by dgfoster View Post
    Agree.

    If you must fix it rather than get a replacement, I'd use an o-ring mechanically compressed between an exterior flat, say 2" diameter, cap made of 3/16" material with a 6 or 8 hole bolt circle for the outside. Cut a circular groove to receive and trap a thick o-ring. For the inside use a split ring of maybe 3/16" (might get by with 1/8") steel drilled and tapped with a corresponding pattern. Fish the split ring inside. Place the cap and run up SHCS screws to draw the cap and ring up snug to the outside of the tank. If you don't trust the o-ring fully, put a bead of silicone rubber on the cap before you draw up the ring.

    OP, I like the new tank better, but that is not the question you asked.

    Denis
    This was my original idea of the best way to fix the tank. The problem is that when the hole was drilled to drain the gas it was done near the edge of the tank and goes into a radius. That is why I was asking about using magic goo to fix it. Monday morning I am going to get on the phone to some of these yards that SteveF pointed me towards. I find it hard to believe that they all have been drilled.

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    If thick enough tap it for a pipe plug.

    Just enough for the plug to get maybe 2 turns so you have plenty of material to compress.

    Maybe some type of epoxy or other magic stuff as thread sealer.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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