to weld or to seam-seal...

[Henry James the 47th]

..that is the question. I've got a little sheet metal work ahead, and have just had the cab firewall on my truck media blasted. Sure enough, there were problem areas that will need further attention. For me, this means cutting out the problems and welding in new metal.

It seems to me that on certain critical areas of the 40 series body, like the joint between the cowl and widshield support - really any seam exposed to the weather, will ultimately succumb to the combination of sun, wind, temperature extremes, and rain/snow. These ravages cause the seam sealer to become hardened and lose the ability to seal the seams properly. Then the rust creeps into the seams.

While I'm sure seam sealers made today are superior to what Toyota put on the cruisers 20-40 years ago, why not weld the seams up entirely? Especially the cowl and the kick panels, which ALWAYS rust out, starting from the seams. Even though the factory chose to use spot welding, why not weld the seam up completely and do away with the problem altogether (this is assuming that all the rust was removed beforehand, mind you). The only objection I can see to this would be form a purist restoration perspective...

 

[gladly]

I think that the reason for using seam sealer is that is gives a bit more flex, which, if welded so that there could be no movement, might turn into crack potential

 

[UNO_RACING]

If it were me I'd weld it, but you could get away with the seam seal too. The only risk with welding is that you might burn through the existing metal and create a larger head ache.

On my resto we welded complete patches (small in nature) and tacked others then seam sealed. It really depends on your or your bodyshops welding experience and the exposure of the specific trouble area to the elements.

 

[Henry James the 47th]

I think that the reason for using seam sealer is that is gives a bit more flex, which, if welded so that there could be no movement, might turn into crack potential

But it IS welded: spot-welded. The panels do not move about in relation to one another, so the cracking problem I suspect to be a non-issue in terms of the seam sealer's function.

I think the flexibility you mention only really takes place in the sealer spanning the seam when the metal undergoes expansion/contraction from heating and cooling cycles. I don't see how a fully welded seam is going to be much more rigid than a spot welded seam, though maybe i'm talking out of my ass here, as I'm not expert on sheet metal dynamics

 

[LC_Hamma]

An excellent product I recommend for sealing cracks/ joints:
http://www.por15.com/POR-PATCH?sc=2&category=148
I'm on my 2nd buildup using the stuff with great results. No cracking or peeling off so far. When they say WEAR GLOVES, they ain't joking around.........

 

[Cammy]

Seam sealer means less welding for the factory. You are correct that spot welding prevents panels from moving in relation to each other. However, the spot weld will alow some flex to the entire panel without breakage. You make the call for your rig but I would just patch the small rust holes you have in your seams and seam seal the rest.
I don't know about Toyota but most domestic cars are seem sealed before spot welding. When welding over the seam you tend to get NASTY slag inclusions as the seam sealer in the seam boils into your weld.

 

[my64fj40]

While my tub was in the primer stage, I took some por15 to all the seams and it worked out pretty good. Pics in my sig..

 

[Henry James the 47th]

Seam sealer means less welding for the factory. You are correct that spot welding prevents panels from moving in relation to each other. However, the spot weld will alow some flex to the entire panel without breakage. You make the call for your rig but I would just patch the small rust holes you have in your seams and seam seal the rest.
I don't know about Toyota but most domestic cars are seem sealed before spot welding. When welding over the seam you tend to get NASTY slag inclusions as the seam sealer in the seam boils into your weld.

That's a good point about residue in the seam affecting the weld

 

[67azcruizr]

I'm concerned with warping my quarter with a full weld with this fuel door, wondering how that POR stuff would work here. also heard about cooling metal with a damp rag after each spot weld, does anyone have any sort of knowledge with welding body panels of sort? p.s. this is a 67

 

[Cammy]

Weld an inch or so at a time to prevent overheating the panel. Cooling an extremely hot panel can also distort the panel due to shrinkage.
I have used a wet rag applied to adjacent areas to prevent warpage with good results. Because it is not a high stress piece you dont need a heavy bead. Just attach your piece with enough weld to be ground smooth. A small amount of body filler to cover the grind marks, primer sand and paint. POR 15 the back of the area when finished.
You could drill several holes in your tank door and spot weld them to the panel behind. You could also apply seam sealer to areas between you spot welds before welding.


Good luck.

 

[Henry James the 47th]

One way to avoid warping is to weld in a series of intermittent, widely spaced spots, and gradually fill in the spaces between them with more short beads until there is a full-length bead. It's a bit similar in some ways to torquing down a cylinder head using a bolt-tightening sequence - diffuse the load over the area.

 

[rukowh]

Welding those seams can also change the temper of the steel causing it to become more brittle thus more likely to crack when flexing. So far I haven't seen many If any places that toyota knowingly tried to cut corners so there is probably a reason for the sealer.

 

[Henry James the 47th]

Welding those seams can also change the temper of the steel causing it to become more brittle thus more likely to crack when flexing. So far I haven't seen many If any places that toyota knowingly tried to cut corners so there is probably a reason for the sealer.

That sounds reasonable, but isn't brittleness of a weld also a function of whay type of rod is used, etc? Some types have better elongation qualities than others - I've been reading about this issue in terms of welding cast, so I wonder if it also applies to heet steel as well. Where are the welding experts out there?

Toyota may not have had any intention to "cut corners", per se, but certain economies apply at nearly any price point. I imagine they chose to assemble truck bodies that way because the method of spot-welding large panels lends itself well to assembly line production.

 

[ToddsFJ40]

You will never find an arc weld on the body of a car. They consider all of the outside panels class A surfaces and thus are not welded. They do weld the A pillars and B pillars to the roof of most cars. This weld is usually MIG welded using Silicon Bronze welding wire as the filler. Silicon Bronze is easily feathered into the panels so that you don't see the Pillar/roof seam.

I work for Lincoln Electric in Detroit as a Welding Engineer. What questions do you have?

http://www.lincolnelectric.com



A link that explains distortion caused by welding. http://www.lincolnelectric.com/knowledge/articles/content/distortion.asp

 

[crushers]

to bring an old thread back to life.
the idea of the "weld through" seam sealer used by Toyota was to seal the joints in the middle. do some research about it.
not the same as the seam sealer being discussed here.
even if you do a full weld seam on an over lapping panel you will have a strong potential for rust between the panels. (1/2" over lap)
discuss...

 

[essar5]

All I can say is seam sealer is exactly what the name implies. It seals seams, gaps or whatever you want to call it. Very similar to caulking in function and appearance. That being said, why would anyone use it as a substitute for welding?
As far as lap welds rusting out on body panels, that's pretty much guaranteed to happen. Layers of steel seem to be a problem area on several of the cruisers I have seen. Where the pillars meet the roof can hide some seriously nasty stuff.

 

[crushers]

yes, i agree, look at a 40 where the over laps are and you will find rust.
troopy series and 60 series roof lines for sweat rusting.
if the seam sealer is applied properly before the spot welds are activated then the panels really shouldn't rust at all. in theory.
no?
the reason i ask is cause i bought a new toy, professional grade spot welder, and my reading is leading me to this conclusion.
there are two trains of thought i have come across, one says weld through primer, one says weld through seam sealer.
discuss.

 

[Henry James the 47th]

My thought on the matter is that, ideally, after welding is done, the component should be dunked into some sort of anti-rust chemical that bonds to the metal, penetrating fully into the seam. I've seen similar processes done with new cars, where the entire unibody is dunked.

The spot weld is going to burn off any coating on the metal in the immediate area, and with seam sealer and epoxy primer, you are not going to get right in there to the weld site in an overlapping join.

 

[shelfboy1]

when i was building bodies back in the 70s i used aluminized steel that didnt rust however the first bodies i made i used regular mig wire and the seams all rusted .
it took years for this to happen .still a couple running around and the body metal is good but the seams rusted .protecting the metal is the best protection i know of .

 

[crushers]

Henry,
I agree, where you actually spot weld any protection will be burnt off but, as a side note, have you noticed it isn't where the spot welds are that seem to rust but between them? i wonder if some of the chemical is actually burnt into the metal???