Seam sealer on underside?

Mopar Body and Trim

  1. GSS

    GSS Well-Known Member

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    None of my Mopars appear to have had any seam sealer on the underside of the car but there are a few places on my Demon that could really benefit from some. Do any of you guys do this?
     
  2. RustyRatRod

    RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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    I'm doing it to mine. Replacing seam sealer everywhere.
     
  3. Swinger340Canuc

    Swinger340Canuc 72 Swinger 340 Special

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    You’ll notice that all the seam sealing is done on the inside of the car and the seams are open on the underside. When you try and seal both side if water does find it’s way in the seam it won’t dry out and will stay wet in there and continuously corrode the seam. I haven’t done this yet to mine but I am going to get around to it is to spray a wax oil product used for corrosion rust proofing in between the seams on the bottom of my car. This product creeps in between the seams and then solidifies like wax. This is the gun that has a couple different tips that sprays the stuff, almost like a mist,
    8021D3DC-FA68-4BE4-BEC2-270146D6FE16.jpeg

    0E88D02C-3A76-4317-9B7C-2D722F40E6A8.jpeg

    This method keeps the seams open so they can dry out but protected from the water. It does wipe off easily when first sprayed from the surfaces you don’t want it on.
     
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    • 4spdragtop

      4spdragtop FABO Gold Member FABO Gold Member

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      So are you spraying the wax/oil product on the seams from underside?
      What product did you use?
      Thanks for the info.
       
    • 69moredoor

      69moredoor Well-Known Member

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      I use a homemade waxoyl on my old jeeps. They are notorious for frame rot. Just make sure all your welding is done before you do it. (IE frame is completely finished). The home brew recipe I’ve used on multiple vehicles is:
      Large old pot
      Jug of used motor oil
      Toilet bowl wax rings

      I use the side burner on my barbecue
      Heat oil
      Break up wax rings
      Mix until melted
      Get the consistency you are looking for. If you want thicker, use more wax
      Use whatever tool to get wax where you need it (turkey baster, garden sprayer)
      It will turn into a frosting type coating depending on the wax ratio

      Just putting this out there as good for thought. On hot southern days my frame will weep a little bit of waxy oil
       
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      • Swinger340Canuc

        Swinger340Canuc 72 Swinger 340 Special

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        Yes Steve from the bottom, and your not trying to fill the seam just mist in a decent film and it will creep into the gaps it can for a time until it finally sets up. If you remember on my thread after I removed all the seam sealer on the inside of my car and blew as much of the loose rust and debris out of my seams I brushed a wet coat of Por15 on them, enough until they dripped out the bottom, and then after that dried I applied a modern seam sealer. Now that went a long way to protect the tight seams but the larger open seams on the bottom can use this wax oil spray to help protect them.
        I used a product by Pro Form but if you do a web search you’ll find quite a few options and many have an aerosol can version so you don’t need the gun.
         
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        • GSS

          GSS Well-Known Member

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          That is what I do after all body/paint work is done. I use Transtar Amber in a rattle can. It is really thin so it gets into the door and rocker seams really well, then dries to a thick coat of wax that does't seem to let dirt and crap stick to it.
           
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          • Tooljunkie

            Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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            I used seam sealer around the flanges,any patches i found and where rockers meet the floor.
            Made sure to blow out all the loose dirt and soaked the inner frame rails with rust convertor wherever i could spray it in. That stuff is like a primer for paint.
            Then paint with chassis black wherever i could hit it.
             
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            • RustyRatRod

              RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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              Well, I guess my crap's gonna rust all to hell. I am seam sealing every nook and cranny top and bottom where I replaced the floor pans. Ain't havin it. I'm sealin everything I can find. A coat of Rustoleum before and after.
               
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              • kursplat

                kursplat FABO Gold Member FABO Gold Member

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                i hadn't thought about "sealing" the underside of the seams,thanks. i'll also be doing the inside of my frame too
                Eastwood Internal Frame Anti-Rust Coating, 14 oz. Spray

                i don't know how old you are, but my cars not going to rust before i'm dead :D
                 
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                • adamm

                  adamm Well-Known Member

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                  I'm just going through this process now too. Floor plans are in and I was thinking to use 3M's seam sealer both inside and underneath. Primer first, then seam sealer, then truck bed liner.

                  If you seal the seams completely, would there be concerns, or does condensation still allow water to be present under all of that?
                   
                • RustyRatRod

                  RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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                  I don't think there would be concerns in your lifetime. I am using Dominion brushable seam sealer on mine and I really like how easily it brushes on. It dries quickly and cleans up with mineral spirits. I am sure the 3M is the same. I have a can of it too but I haven't gotten to it yet. I will before it's all done.
                   
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                  • Bodyperson

                    Bodyperson Pedal to the metal

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                    • 4spdragtop

                      4spdragtop FABO Gold Member FABO Gold Member

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                    • Bodyperson

                      Bodyperson Pedal to the metal

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                      No sir. It a lot like others are talking about like the cavity wax but it dries harder and has excellent creeping characteristics. I've done tests with it and it will climb 4 inches up an aluminium can. I don't think it will hold up to an abrasive type salt test but for between seams that get sealed it is an excellent product or for interior work. And it wont keep leaking when it get hot. I use it along with this.
                      https://www.amazon.com/dp/B00KNCD32M/?tag=joeychgo-20 and then paint.
                       
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                      • RustyRatRod

                        RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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                      • barbee6043

                        barbee6043 barbee 6043 FABO Gold Member

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                        I just ended up after all that paint work to underside, I undercoat it like the factory did!! !ha
                         
                      • Bodyperson

                        Bodyperson Pedal to the metal

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                        Guaranteed work aint cheap. Punch that card you cheap *******.
                         
                      • Bodyperson

                        Bodyperson Pedal to the metal

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                        • 4spdragtop

                          4spdragtop FABO Gold Member FABO Gold Member

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                          Heres an old can of 3M. I keep it in my shop display cabinet...looks about 30 years old.
                          Cleanup " with unleaded gasoline " lol

                          20190728_133423.jpg

                          20190728_133434.jpg
                           
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                          • GSS

                            GSS Well-Known Member

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                            I would avoid the bed liner and underneath seam sealer unless you are building a daily driver. If you use seam sealer on both sides of the seam, make sure there is no air trapped in there.
                            Just noticed you are in Duluth too, :thumbsup:
                             
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