The corroded seam, about 15 inches long, that I am trying to fix is on the outside edge of the passenger rear floorboard. I have seen this same seam damaged in about 4 or 5 W123s.( So please forget abou the idea of cutting one from another car!)
The front of the seam is only one inch behind where the front passenger side seatbelt bolts to. It runs straight back and the rear of the seam is the just prior to the hump where the bench seat of the rear seat rests.
Inspection of the damaged area from underneath reveals that the steel in this area was stamped and has several wells and raised points and is not a simple flat plain surface. Also it was covered with undercoating and really needs to be grinded!
Inspection of the damaged area from the top shows that two layers of steel are damaged. The first layer is the floorboard I just mentioned and the second layer is an inner area that forms the door edge hump.
I have heard that floorboards should always be repaired by welding from the bottom. Should I start grinding the area from underneath meanwhile?
I have at least a month before I finish reading my Haynes Welding manual and practice with my equipment, but i would like to start the surface prep now.

I wouldn't leave it exposed for very long as you know it will rust quickly. However, you can spray it with metal prep which will protect it for a little while.

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

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

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

and saw a Lincoln MIG with Gas unit,for $700, I was tempted to buy it on the spot ( it was out of box and normally 1000 ), but I'm pretty level headed with the Credit Card, and I didn't..it sure is hard to find a good used welder at 220 with gas and MIG, because they disappear instantly but I 'm going to be patient about this..

As I grinded and prepped the seam, I would spray primer on it to protect it temporarily until the day of the actual weld. I'm tempted to start grinding now, in case there is more cancer than I first expected...

...in case?

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

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

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

Rich,

Just so you know. Lincoln is not known for their wirefeed welders. They make good stick welders and the boys on the pipelines really like their gas engine powered welders, but Lincoln is just not the best for a wirefeed.

Miller makes Hobart and they are known for their wirefeed welders. If there is a TSC store near you they have a special Hobart package that is not available anywhere else. It includes a Hobart Handler 180, an auto darkening helmet, a cart, a small CO2/Argon bottle, gloves, a chipping hammer and a steel brush for a little over $600. Now that Christmas is over you might can even get it cheaper. The helmet, if bought separately, is a $139 helmet.

An auto darkening helmet is a BIG advantage for a beginning welder.

I would strongly recommend that you look for one of these packages or at least come up with a Miller or Hobart if you are going to get a MIG welder.

Welders are an item that is VERY difficult to find in good shape on the used market, and when you do find one you will pay nearly a new price for it.

BTW, watch your mailbox for the next few days.

Have a great day,

That deal that Larry mentions is the best I've heard of. You're gonna waste a lot of time trying to find a better deal than that, and you probably won't find it. Really. Spend that time welding instead.

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

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

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

That is pretty darned funny. I was thinking the same thing....Although like you said its common these cars..If its any consolation my car has a similar issue.....what is the saying? what the welder adds the grinder taketh away?

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Rob M
Norwich, VT USA
1980 240D Euro delivery 4 speed manual silver/blue
~160K miles

THANKS LARRY! Well see, I was Lucky. I didnt rush out and buy the first machine I saw. I saw all these $199 units at Home Depot and Loews.

I decided to read all my welding books that I ordered first.

Welding is big stuff in the USA. People even have Forums for underwater welders and welders run by Huge Diesel Engines. I've used powerful tools in my Life--but seriously a Diesel powered welder---isn't that something that would be say around 1000 Amps?
And maybe enough to weld on a skyscraper?
I mean just in case, thats all I ended up with,a 1000 amp Diesel powered welder, would a welder that powerful be able to discharge lightning bolts or even start a tornado if I did not adjust it right?

The patchwork I am doing in this area will get a floorboard to side panel patch that is welded in from the top. More than one piece of metal actually, because the rust is pretty long down that waterway. Once this patchwork is in place and sealed and painted or otherwise rust treated (POR-15), then I can drive the car.

Later when the weather is warmer I can go back with a second patch of sheet metal on the outside under the car, should I decide that the rocker panels need to be closed back up. But it may be easier to clean out and monitor for rust if this is not closed up.

Same thing on the driver's side with the new stamped floor board. That is welded in from the top.

The disadvantage of doing the repair this way vice welding from underneath is being sure you get the underside of the repair sealed against rust, since it typically comes in contact with water, salt, etc.

The advantage is ease of repair and less metal to cut out, and it's much easier to prepare the interior metal for welding than the undercoated underside of the car.

But a professional repair - it's not.

Ken300D

P.S. In some cases I may have to seal an area with another, lighter gauge patch of metal because of the irregularities you mention in the floor's surface. The main patch is for strength and most of the seal, with a lighter patch to complete the seal.

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

Rich,

There is a good welding forum at www.hobartwelders.com Click on the Weld Talk button at the top of the home page.

Enjoy,

And to add a little more to what Larry and Pete have to say...

I saw this Hobart special at TSC the other night (not much else to do all alone in Sault Ste Marie on a Wednesday night), if I didn't already have a Hobart mig welder I would have snapped this one up. It has everything my rig came with (except I didn't get an auto-dimming hood) for about the same price I paid.

I also noted that TSC has a mighty nice 48" brake as well as a shear. I might end up buying one (brake that is) here in the Soo and shipping it to CA if I find there isn't a TSC within a hundred miles of the house.

What can I say, window shopping at the TSC is my new pastime.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Born and bred in Southern California, I have no idea what a TSC store is.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

check out homedepot for the miller 220v mig that comes with everything but the gas. much cheaper than anywhere else i have seen. thats the unit i am planning on buying.

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have no worries.....President Obama swears "If you like your gun, you can keep it

This is a structural repair, not a pressure certified weld.

It does not need to be air/water tight every millimeter, and that is not desirable with unibody flexibility in mind.

Strength is what you need, Mercedes does not solid weld these cars together.

Mercedes uses metal coating, adhesive, sealer and rubber undercoating to seal out water/corrosion.

Do not get stressed, or carried away with the fun of making sparks.

Heat is the friend/enemy of every welder, learn to use it and respect it.

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ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

I have the exact model mentioned but in a 120v unit and I love it. Paid around that money for it and it is sweet.

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83 300CDTurbo 307,000
2005 Honda Element 266,000
56 Nash Ambassador Country Club Special 34,000(under restoration presently)

http://www.peachparts.com/shopforum/car-audio-multimedia/125099-123-install-extreme-dynamat.html