2004 Expedition - help me identify this rusted box driver side rear corner

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JamaicaJoe

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Weird. Maybe that corner was too difficult to mate using sheet metal and the plastic plug is simply a joiner?
 
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whtbronco

whtbronco

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Weird. Maybe that corner was too difficult to mate using sheet metal and the plastic plug is simply a joiner?

Yeah maybe so. It is kinda weird. I know from Hamfisted that his 2003 does not have that box. My thought was maybe the 2003 was found to be weak there and this supposedly helped. It's plastic inside and sheet metal outside. I really don't know.
 

JamaicaJoe

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Yeah maybe so. It is kinda weird. I know from Hamfisted that his 2003 does not have that box. My thought was maybe the 2003 was found to be weak there and this supposedly helped. It's plastic inside and sheet metal outside. I really don't know.
I recall reading an Expedition Brochure at some point where rollover safety improvements were performed at some model year. They included injecting some closed cell foam into the perimeter roof channels and the pillars A, B,C,D etc. I was going to mention, be careful welding where there is foam.
 
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whtbronco

whtbronco

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I recall reading an Expedition Brochure at some point where rollover safety improvements were performed at some model year. They included injecting some closed cell foam into the perimeter roof channels and the pillars A, B,C,D etc. I was going to mention, be careful welding where there is foam.
Well that would certainly make sense and fits with what I found both on the truck and the description of the part number. Very interesting, thanks for sharing the info on the brochure.

So is the concern with welding around foam the risk fire, toxic fumes or is there something else? I'm not too concerned, the foam has been removed everywhere I will be welding except where there are currently 2 layers of factory sheet metal that remain. I'm also just kinda doing a tack weld, so while it will still get hot it won't be for long. My plan is to put panel bond around the edges to both seal it up from tire spray and reduce the welding required. I punched quite a few holes, but I will probably just weld like 6 of them.
 
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whtbronco

whtbronco

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Well I had held onto a good size piece of the foam and after about 2 seconds with a lighter it caught fire. So it's clearly quite flammable. I'll have to be cautious for sure. I always keep a fire extinguisher with me when welding.
 

JamaicaJoe

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Well I had held onto a good size piece of the foam and after about 2 seconds with a lighter it caught fire. So it's clearly quite flammable. I'll have to be cautious for sure. I always keep a fire extinguisher with me when welding.
Yeah, I have no idea how body shops deal with that risk. You need some sort of flame stop to keep fire from going up the pillar like a chimney.
 
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whtbronco

whtbronco

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Agreed. I'm just gonna have to take the approach of preventing the foam from getting hot enough to catch fire. 3 sides of the repair area have no foam behind them so I have little concern there. It's really just across the top. So I'll work around it or find a way to separate the foam from the metal. I'll let ya know how it works out.
 
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whtbronco

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This repair has been completed. I was able to tack weld each hole I punched in the repair panel except 1. That 1 had foam right behind it that would very likely have caught fire so I just skipped it.

I did not worry about making it look good. It just needed to be structurally sound and all the rust needed to be removed. Besides the fact that it didn't look good to begin with, it's out of sight and grinding/welding above your head laying on your back just sucks. So I limited the amount of sparks and liquid metal that were falling on me. I only had 1 cherry that managed to find it's way into my clothes.
 

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