Okay, I need to gather all the materials I need to replace my floor pan. That would include.

Plasma Cutter
Welder
Grinder (for removing current pan and surface rust)
Used Floor Pan
Seam Sealer
anything else?

Once we've welded the 'used' floor pan into place, patching the old rust, I was told we need to apply seam sealer. I have no idea what seam sealer is, or where to buy it, or what kind to buy?

Any tips? Is there anything else I should consider doing in this process? Maybe POR15?

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1995 E320 Sportline Wagon "Bernard"
black on black leather

http://i.imgur.com/BdZ7jM3.png

Seam Sealer is used to seal seams ( duh!). The kind you want is the brushable, with a brush built into the can lid. One source is eastwood.com Eastwood is a supplier to the auto restoration hobby.

Don't apply the seam sealer over any rust on your replacement panel. POR15 would be a good move in any event.

..and watch out for fires - I set my hair on fire replacing a floorpan. Keeps the neighbours amused.

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'79 280SE
'87 560SEL
'83 280CE
'01 Nissan Micra
'98 VW Passat
'83 911 turbo

What in the world are you going to use the Plasma cutter for ,they work very poorly on painted metal and even worse on undercoated metal.I had a very good industrial model and it was fine for clean sheet when you had a large volume of work to do . What you need is a saws all and a mig welder and maybe an angle grinder with a cut off wheel...... You have to pay at least $3500 to $5000 for a good plasma cutter the 900 dollar ones are expensive toys...........

William Rogers.........

I agree with William. If you are setting up an industrial shop then by all means purchase a high quality plasma cutter but if you will only use it every now and then use the sawzall and and angle grinder. In addition to being expensive to purchase they are pretty maintenance intensive.

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Jim

Have never replaced a pan section in a Mercedes, but have done several Mustangs...
A Sawzall will make quick work of removing the old pan section...
My advice is to have a good set of hearing protectors on... you won't believe how loud it it inside the car when you start cutting.
Also, plan and look (on both sides!!) before you cut. When you're convinced its OK, stop and check again. It makes the job a lot more complicated when you cut a brake line or electrical harness in half while cutting (don't ask me how I know).
Rather than try a butt weld, I'd recommend you allow about an inch of overlap all around for strength and ease of welding. You won't win a concours event, but it will be strong. If its a large piece, rather than seam weld it all the way around, I usually spot weld it with a MIG welder. Easy to do with the "overlap" method... simply drill a number of 3/16 inch holes around the edges of the larger panel. When you set it in place, just use the MIG tip through the hole to hit the bottom panel and butter the hole closed.
Another trick is to use a "flanging" tool... this puts an offset into the edge of the new panel so it sits in the hole properly and is flush underneath.
I use good quality automotive seam sealer on the top (inside the car)... Eastwood's is fine.
On the bottom of the car, I use asphalt based roof sealer (comes in caulk tubes) to fill the small groove thats left there. A quick run around with a putty knife will level it out. If the car is undercoated, when you recoat the area it will disappear.
Important that the repair be watertight so spray doesn't soak the interior carpet/pad.
Oh, did I mention to look twice on both sides and cut once?
Hope this helps.

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KenP

1996 S500 W140 Coupe

Hey, some really good answers so far....
I sure agree that for this job a plasma cutter is not appropriate ( unless you just want a plasma cutter and are using this to sell the concept to the wife... in that case far be it for me to interfer )...
For a tight space maybe the smaller version of the Sawzall would be handy.... the air powered high speed sheet metal cutter.. cheap and very useful...
I really agree with the flanger... I own one I only gave $30 for in a pawn shop... amazing tool... one direction it flanges and turn it around and it pops out a perfect little hole for plug welding into .....
Also high on the nice to have around are " clecos'... these are little things which will fit into ( typically ) an eigth inch hole like a pop rivet would ... but can be taken out and moved around... this helps to make sure the entire pan is level and properly placed before any welding or things hard to undo are applied to the project...
If you get the Eastwood catalog and read ( drool ) it through you will get lots of ideas for this project...
Also is the catalog from "aircraft-too.com" 1-800-248-0638..... the guys that mess with Experimental ( home made ) aircraft really get into this sheet metal / riveting stuff... ( or they die soon afterwards )....
Check the library and see if you can find the book by sheetmetal wizard Ron Fornier.... amazing guy with magic hammers in his shop....

Remember, to use Cleco™ plier-operated sheet metal fasteners (or skinpins), you'll need an appropriate set of skinpin pliers to install and de-install them.

More tools!

M U S T H A V E M O R E T O O L S ! ! ! !



Clecos are a really nice way to hold pieces for assembly (http://www.performancebodies.com/2002%20catalog/rivets/rivets.html#cleco)
but, I'd probably just flange the replacement piece, get it where it needs to go, drill a few holes through both pieces and temporarily POP™ rivet the part in place to hold it while I welded.

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Never a dull moment at Berry Hill Farm.

Well, sure , Randy,,,, you have either a wife, daughter or son or neighbors you can call on for the tough alignment stuff...
One real problem with pop rivets is if you happen to stick one too long into a hole and ' install it'.... then if you need to take it out it just turns with your drill bit...
Or, the clecos are good for tight spaces where drilling out would require the use of a 90degree head drill and stubby drill bits.. not something everyone has laying around...
Fortunately the pliers are only about $7 I think,,, but will work with a really wide assortment of holders... and they are a ONE HAND take out ... good because my other hand is usually occupied holding the item....
I do not see pop rivets or clecos as replacement for flanging... flanging is the strongest , easiest combo method I know of for this type stuff... make the holes which will be used for plug welding or brazing... use the clecos and flanging to get the fit proper and measure 6 times to make sure before you weld it....
I have owned my clecos since 1979 when I had to drive to Dallas to buy them.... they are particularly wonderful for one man operations....