This is my first time welding. I just bought a Hobart Handler 125 Welder 110VAC and I am excited about fixing my floorboars. Wow the small seam that was cracked turned into major cancer! Somewhere I vaguely recall reading that floorboards should be welded from below.
Should I place the metal above the hole or below the hole?
Should I weld from above the hole or below the hole?



Here is a view from above.


(Believe it or not I am driving this car this way everday to work, the theory being that as long as I have to drive it, the faster I will fix it!)
W123 300D Floorboards:weld from above or below?

I'd do most of it from above. It's easier than doing it on your back, especially for a beginner. (unlike some other things ) Do peel back some of that undercoating at least 1" from the edge first though. I'd place the metal ABOVE the hole. That way, you can tack it down in a few places, then push nearby loose edges with a big screwdriver as you tack it down. If you use something like 18 gauge, the floor will still be strong enough, yet you'll be able to form it in situ somewhat.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

GEEeeeEE Whiiiizzz!!!!!

I will never complain about the the Texas heat in August ever again!!!! As a carnut, I am sooo glad that I don't live in rust country. You carguys in salt country have LOTS of guts and determination.

It took me quite awhile to load those pictures on my boondocks 22K dial up and now I'm so sick I wonder why I went through that pain.

So, as you can tell I have ZERO experience repairing rusted out cars. I do however have experience welding and patching stuff. I agree with Petes suggestion. I would grind everything VERY clean and tack it down in a few places all around while holding the metal down with the big screwdriver as he suggests. THEN make short welds halfway between each of those tacks. Then go back around making more short welds halfway between those tacks and so forth until you get it all welded together. Then go underneath with a generous amount of that spray can undercoating after the job is done.

Also I don't know if your welder is set up for gas or only for flux core, but I personally would NOT use flux core. I would use Argon/CO2 and .030 ERS70S6. For this job you really also need a good, comfortable auto darkening helmet.

Best of luck and keep us posted,

I had mine welded together at a small body shop (not a collision shop, this guy is actually restoring a '57 MB convertible for another custumer right now) He welded the pans from both sides, one piece on top and one from the bottom. I think there's no better way to do it, the question remains is if this effort is necessary. At least I can be sure that I don't have to do it again in probably 20+ years. Downside is the price I paid: $1500 for three floor pans, some work around the two jack holes right side and a huge gaping hole behind the right rear wheel inside the trunk.

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'99 S420, 155k
'91 VW Vanagon GL, 150k
'85 VW Vanagon GL, 120k
'82 VW Westy, aircooled, 165k

So all that typing I did concerning offset flanging the good metal, making holes for both plug welding and rivets was for nothing it looks like...
If you punch the holes in the new floor then it would be an obvious choice to weld from above/inside. When you predrill and prepunch the holes in the new piece of metal then it is a simple deal to use those holes for perfect drilling of the metal behind it.

The location of the rust suggests that the car has had water coming into the passenger compartment, so when you get it fixed you might continue to watch for incoming water.

I'm starting out with new metal panels welded in from the top. On the driver's side it is an entire new aftermarket floor pan plus additional tie-in patches. On the passenger's side I'm just using patches as most of the pan is still good. A sheet of 18 gauge metal has been the most useful material for me so far, it's quite strong when welded into place. A tool that has been really useful for all of this patch fabrication work is an "air nibbler". This is an air compressor powered device that nibbles away at the metal as you push it along. This gives the overall effect of a power knife through metal, with little distortion of the metal as you might get with tin snips. Great tool.

Hobert also sells .240 welding wire for MIG work. Along with that you'd have to buy the right .240 adapter for the welding gun. I have not compared the .240 wire with the .030 wire on sheet metal welding, so I can only guess that the .240 wire is a little less likely to cause a burn-through hole. I did some welding with the .030 wire by joining two ends of short sections of square steel tube to make a longer piece. I'd say the .030 wire had good penetration on that work, perhaps that is the difference between the wire sizes.

Please be aware that the undercoating is flammable. Keep a fire extinguisher or water hose close by. I am in fact quite shocked that it is so flammable, both the undercoating and the materials used inside the passenger floor pan. Since I found that a propane torch is quite useful for softening and removing this undercoating, I have to balance the use of the torch with the knowledge the whole car could catch on fire if I'm not careful. So be prepared with at least water.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

This is great advice from Ken - I won't do ANY welding on a car unless I've got a person standing by with water and a fire extinguisher. It's just way too easy to lose track of whats happening when you are wearing a welding mask. Your welder is capable of creating enough heat that almost anything in the car can quickley catch on fire. You should also have the car set up so that you can IMMEDIATELY roll it out of the garage if things go really bad - Don't have it up on jack stands with all the wheels removed and three cars blocking the garage exit!!

Thanks for your answer. Anybody from Delaware has got to be a nice guy!

Ever heard of Joe Biden?

Congrats on the welder I still smile sometimes when I think about mine.

As has been said already but I think it is worth repeating: make it easy on yourself. I would weld from the top, seam seal and undercoat from the bottom. The cleaner the workpiece, the better and easier the weld. Look at the backside of your weld to see if you are getting adequate penetration.

Don't worry too much about the appearance of work that nobody will see.

Be safe. Also worth repeating: don't breath the fumes from welding or coating or the dust from grinding.

Pay attention to the ground path for the weld. For example, if you ground the welder across a bearing you will fry the bearing. Any resistance in your ground path is an electric heater when you pull the trigger.

I posted somewhere here about puddle welding. If this doesn't ring a bell it is probably worth searching to review the concept.

I don't know Joe Biden that well, but he seems like a nice guy. I actually shook hands with him once. Of course, I am kind of naive and I don't judge people well.. I think one of the reasons he is running..ah well, I will stick to cars...At least Mr. Capano isn't running...Boy this is getting dangerous and I better stick to CARS.
As for Delaware, I really think its a nice place, but recently its been growing like CRAZY, especially Northern Delaware. I grew up in Claymont and left for 15 years and when i came back I didn't recognize downtown Wilmington...I couldn't find more than 1 or 2 of my high school classmates, everyone left. It was kind of sad, because I have a lot of great childhood memories...

Joe Biden is Delaware's version of Ted Kennedy, but without the shame.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Seriously, I am trying to understand American politics so please help me. Why is Joe Biden being compared to Edward Kennedy? I'm seriously naive and trying to learn.
Aren't all high profile politicians who are effective often castigated and villianized?
To name a few, Mayor Guliani of NYC; William Jefferson Clinton, our former president; Senator McCain, a possible president? Part of their personality chemistry is always colorful. That goes back to Mayor Jimmy Walker of NYC (?1920) and FDR, JFK and LBJ. They all had a bit of villian in them and ruthfulness and meanness and even monster in them.
I mean people like Jimmy Carter and Gerald Ford are really nice honest people, but I dont think any statesman in this Ugly world we live in can rule effectively without a bit of ruthlessness, ugliness and meanness in them. With that comes the women and the Scotch..
Do we really want Al Gore for president? He's obviously a gentleman, intelligent and capable, but when it comes to the skullduggery and Machievallian things you need to do to deal with the thugs in power in Russia, Europe, China and the Middle East, it atkes a B__ As_ to kick as__. With that kind of person comes mischief.
AmI wrong? well i guess thats realted to Floorboards because I'm using the NY Times to cover the hole when I drive.

Well, actually I can't remember what it was that caused Joe to withdraw from presidential aspirations some years back, but I sort of remember it was sort of brazen. Of course, Ted Kennedy really has the corner on hypocrisy in the US senate. Not that I like everything I expect from nominee Alito, but Kennedy has some nerve pontificating about a college membership in a group which had some unseemly ties to bigotry. Everyone has some skeletons in their closet, right Ted? At least the guy didn't cheat on his wife, drive drunk, kill someone and then lie about it for half his life, eh?? (google Chappaquiddick)

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.