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Speedymaru

Any ever fill the bed “seam” with body filler?

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Hey, I’m getting close to laying down some paint, and I’m currently finishing up some body work. I’ve had to do a ton of body work on the bed, due to rust, and I’m wondering if anyone has ever filled that weld seam on the lower part of the bed? Any pros or cons of doing this? I’ll try to add a photo of the seam I’m referring to. Thanks 

D8FCA463-2F7F-4D94-8EC1-1BE6EC819F52.jpeg

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So after some more research, it sounds like body filler would crack out pretty quickly. I have a welder but I’m not a competent welder lol. 
 

So another question is, what tool would be best for cleaning out that seam from fiberglass filler? 

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Use a product called 'Drip-Check'. It's made for that purpose. Stays flexible enough to not crack with the minor movements of the panels but surface hardens enough to take and hold paint. Should be a number of different brand names. Might also be called rain gutter sealer. Any good auto supply facility that sells paint, primer, thinner, plastic filler, etc. should have it. Run the right size bead along the body seam and run a finger over it to force down in the seam and flush it up with the panels. Clean off any excess with a rag moist with thinner. It'll sink slightly into the seam as it dries and hardens. An example:

 

https://www.amazon.com/3M-08531-Heavy-Drip-Check-Sealer/dp/B001C7RTCW 

Edited by difrangia
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I haven't done it either personally but this seems like something a seam-sealer would do perfectly - same thing they'd use to fill in the rain gutters/channels on older vehicles, then paint over. I know most people say to weld it but I'd hate to do that job too..

Clean it out as best you can and lay some seam sealer in it is my vote.

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On 9/12/2020 at 2:16 PM, Speedymaru said:

So after some more research, it sounds like body filler would crack out pretty quickly. I have a welder but I’m not a competent welder lol. 
 

So another question is, what tool would be best for cleaning out that seam from fiberglass filler? 

Self leveling seam sealer. It's a 2 part epoxy that bonds as well as seals. It was made just for this type of application. You need a $60 applicator gun and the epoxy itself is about $60 per tube, but one tube will probably do the whole bed.

 

There are tricks to using this epoxy. I tape both sides of the joint with green tape and pull it before the epoxy starts to set. If you pull it too soon it may drip. If you pull it too late you run the risk of either pulling the epoxy with it or never getting the tape off. Once the tape is off, if the epoxy has any imperfections, you can smooth it by dipping your finger in some thinner and run it along the seam.

 

One drawback to this is that the self leveling sealer works best while laying flat, so it would be best to rotate the bed so the side of the bed is horizontal and do one side at a time.

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On 9/12/2020 at 9:05 PM, klam07 said:

I haven't done it either personally but this seems like something a seam-sealer would do perfectly - same thing they'd use to fill in the rain gutters/channels on older vehicles, then paint over. I know most people say to weld it but I'd hate to do that job too..

Clean it out as best you can and lay some seam sealer in it is my vote.

Welding has too many pitfalls. You run the risk of panel warpage with a seam this long.

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7 minutes ago, Stoffregen Motorsports said:

Self leveling seam sealer. It's a 2 part epoxy that bonds as well as seals. It was made just for this type of application. You need a $60 applicator gun and the epoxy itself is about $60 per tube, but one tube will probably do the whole bed.

 

There are tricks to using this epoxy. I tape both sides of the joint with green tape and pull it before the epoxy starts to set. If you pull it too soon it may drip. If you pull it too late you run the risk of either pulling the epoxy with it or never getting the tape off. Once the tape is off, if the epoxy has any imperfections, you can smooth it by dipping your finger in some thinner and run it along the seam.

 

One drawback to this is that the self leveling sealer works best while laying flat, so it would be best to rotate the bed so the side of the bed is horizontal and do one side at a time.


Thanks for the info, I appreciate it

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I'm late to this, but yeah bondo cracks, fiberglass eventually fails

 

I have used a ton of two part polyurethane sealants and joint fillers in concrete construction. You can make a big expensive mess really fast!! I tried an acetylene plumber's torch and 50/50 bars of solder used for sheet metal guys. I thought I cleaned the crap out of everything in paint prep. I used PPG DP epoxy primer and PPG primer surfacer, then Color/Clear coats. It looked and worked great for years. But eventually something started bleeding out from the seams discovering the paint. Then the paint began to ripple and fail. Somehow the flux I used the joint or the flux in the solder began to corrode behind the solder. Or else there was rust way back in the joint that you can't get at. And even using PPG Metal cleaner and Conditioner, it didn't arrest all the rust. What a mess. What a waste of a paint job.

 

My vote is to weld the seams. You definitely can't weld very far before you need to skip around, or just quit until the panel cools. You have to have the right set-up to, maybe even practice unless you are a real badd-azz welder. It's a nasty job... but one you only do once.

 

I'm working on my truck again, and thinking about how to fix my situation. Thinking about welding a strip of metal an inch wide over the seam... then bondo the fuck outta it. 

 

I learned my lesson; Spending money on painting a Datsun that you daily drive will lead to heartbreak...

 

3 words;  Rustoleum Midnight Blue 

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I think there are three pieces, top bottom and the bed floor, that all beet and are spot welded together. It's inevitable it will rust and it will never stop. Rust swells between spot welds and lets in more water and it rusts faster. Solder would work if you can tin it properly. Or stitch weld with a MIG and grind it down. If perfectly sealed a skim of filler..

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55 minutes ago, Figbuck said:

I'm late to this, but yeah bondo cracks, fiberglass eventually fails

 

I have used a ton of two part polyurethane sealants and joint fillers in concrete construction. You can make a big expensive mess really fast!! I tried an acetylene plumber's torch and 50/50 bars of solder used for sheet metal guys. I thought I cleaned the crap out of everything in paint prep. I used PPG DP epoxy primer and PPG primer surfacer, then Color/Clear coats. It looked and worked great for years. But eventually something started bleeding out from the seams discovering the paint. Then the paint began to ripple and fail. Somehow the flux I used the joint or the flux in the solder began to corrode behind the solder. Or else there was rust way back in the joint that you can't get at. And even using PPG Metal cleaner and Conditioner, it didn't arrest all the rust. What a mess. What a waste of a paint job.

 

My vote is to weld the seams. You definitely can't weld very far before you need to skip around, or just quit until the panel cools. You have to have the right set-up to, maybe even practice unless you are a real badd-azz welder. It's a nasty job... but one you only do once.

 

I'm working on my truck again, and thinking about how to fix my situation. Thinking about welding a strip of metal an inch wide over the seam... then bondo the fuck outta it. 

 

I learned my lesson; Spending money on painting a Datsun that you daily drive will lead to heartbreak...

 

3 words;  Rustoleum Midnight Blue 

 

Sounds like you used acid core solder and didn't get all the acidic flux out afterwards

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Welding shrinks metal, period, so unless you are experienced with the process, it can be a real mess. The best way to weld it would be with a TIG as the heat is very focused. MIG heats too much surrounding metal resulting in shrinkage. Sometimes you can control the shrinkage with short stitches and cool off with air, but the quick cooling then hardens the metal which can lead to cracking.

 

Even if you successfully welded the seam. how would you finish it? Would it be completely smooth or do you want to see the body line? If smooth, that's a lot of welding. If you want to see the line, how do you get in there to grind it out?

 

Here's a link to the SEM epoxy I use - https://www.semproducts.com/product/dual-mixtm-self-leveling-seam-sealer/sealer

 

And here is a shot of the cowl to firewall seam on the CJ5 I restored a couple years ago. I'll post one of bare metal and one after paint so you can see how nice the epoxy works.

 

74_CJ5_Body_Work_Small_109_zpsmvwzencr.j

 

CJ5_Final_Assembly_Small_84_zpszehu8qvp.


Final_Assembly_Small_011_zpseebqd3bh.jpg
 

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Silicon bronze TIG welding the seams seems to be the way to go. Its a softer material so easy to grind. Depending on the depth of the weld, you could keep the seam visible. In the future, I plan on doing exactly that. In order to avoid rust from forming in between the panels, I will cut as much of the back panel pinch as possible once welded.

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Again, that's the beauty of the panel bond type epoxy sealer. It flows into the seam and actually bonds to the metal. New cars are built this way with spot welds used to hold the panels while the bonding agent dries. Once it hardens inside the seam, it would be decades before it would begin to fail, and only in harsh conditions.

 

 

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