Might want to take care of the rust in those most recent pictures. If you have to patch big holes of door dont you think its a waste of time and should locate another door?

But if you insist I would weld patch pieces of metal, smooth out with bondo and paint it.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

The trick to using POR15 and fiberglass is to lay down a thick layer of POR15, let dry until tacky, lay the mesh across the hole, apply another layer of POR15. Let dry until tacky, lay another piece of fiberglass mesh at an opposing angle and let cure. Smooth in a thin layer of the POR15 putty, embed another layer of fiberglass mesh, let dry and sand smooth. Finish off with a coat of POR15 or any good primer and top coat.

If you take your time and are skimpy with the POR15 you'll never even notice the repair.

You will go through a stack of latex gloves and disposable brushes but what the heck! Much cheaper than skin replacement and a pint of the POR15 thinner/cleaner.

this is why it was recommended to me to purchase 1/2 a mercedes floor pan! they just sawed that carcass in half. it was up to me to cut appropriately and weld into place. there were a few other places that required patches, but for the most part, i welded 1 solid, rust free piece in and just did a few patches here and there to take care of the rest

i like por15 + fiberglass but make sure its in non-structural areas! and wear a vapor mask and vent the air out. that stuff is not good, unless you were a paint huffer in your previous teenage years

edit: it looks like your welds could be a little hotter. good that you are tacking, but it looks like you are not pulling or pushing your welds, just tacking. it's effective, but man, you must be getting tired tacking all the time, no?

my setting for the floor plan on my lincoln 120V welder was C + 4. easy to remember

For 14 gauge metal, the my Lincoln Pro-mig 135 calls for D-7, but I'm only using .025" wire, maybe that's an issue? How does wire feed speed affect a weld?

I'm fine tacking, as long as I'm not burning holes, which is usually what happens with pushing or pulling.

I think I might weld it all just because I'm better at that. I just can't seem to get the fiberglass to work well enough. I'm just going to make as big a patch as I can and finish it with littler patches.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

JE,

Hows your repairs coming along? any new pics?

Haven't done any work over the winter- no time or space and it was damn cold. I should be starting again in the next few weeks. Floors first, then I'm getting replacement cut-outs of the front sections of the rocker panels from a rust-free donor. Do you happen to know the answer to the above question?

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Which one? Wire feed? or any new pics?

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

Yes, how wire feed affects the weld. How about wire thickness? I've been using .025" and I don't think it was penetrating enough, so I bought some .030".

My next project is going to be rear passenger side. There's a long hole that started in the rocker-floor pan seam. It's about 2" wide and 1 1/2' long.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Well, we had some heavy rain and the Merce took on a little water when I drove through 10" of water, so I took out the carpets to let it dry... then i wanted to take out the back seat to see what was under there, and, well, I got a little carried away.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

More pics.

Does anyone know a good way to get up the insulation on the front floor pans? I tried a heat gun, which is good for the stuff in the rear, but it just burned the front stuff.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

I used a chisel and hammer to remove the undercoating. A good deal of it will come up in pretty big chunks.

__________________
Chad
2013 Jeep Unlimited Rubicon
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL

Alright, I've learned that the welder is more of a feel thing. I'm using .035" solid wire because I though thicker wire would help penetration and lay down more material than the .025" I was using 16 gauge to patch and I was using the settings the welder recommended, but it just wasn't penetrating well enough, so I'm taking matters into my own hands. Higher heat-better penetration, as long as you're not blowing holes.

Now in the picture, I want to remove the front seat support (red) to ease the the patching of the hole underneath (green). I've been working on the hole circled in yellow. I also think the whole pan-rocker seam is infected, so I'm going to cut that whole thing out.

Does anyone know how difficult it is to take off the center console? And how bought that floor insulation? I'm really hoping someone has a good way to get that stuff up, cause it is busting my balls right now.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Alright, I've got two patches done, a fair amount of metal, the pan seems much more secure. I've still got to do that spot near the sub-frame mount.

I read that with using gas, the metal should be clean. I get it pretty clean, remove almost all the rust (I might be welding some rust-pitted metal, some rust could still be in the pits), and I spray on some water based degreaser, rinse it off and wipe it up. Cleaning is a pain in the ass, especially for painting. I've heard good things about POR-15's marine degreaser; does that require rinse? Does anyone have any other recommendations?

As for painting, I've decided to use this "rust destroyer" they have at the auto parts store. Relatively cheap and I think it's like what POR-15 has but separate. I used POR-15 before, but I like to spray, so i'm gonna do rust destroyer and then regs primer and paint. I wanted to get that weld-thru primer, but it was more than 30 bucks for a can! Is it really worth it? I'd only use it on spot and lap welds, but I do mostly butt welds.

For shaped pieces, I've been welding on a rough patch in places and then hammering and grinding to fit. Does anyone have a better way? My way is frustrating, time consuming, and not that good. Also, I'm looking at my last patch, and I think I'm going to have to redo a fair amount. Welds are too cold--not enough penetration, and that fiberglass is terrible. Paint isn't holding on too well either.

I could really use the feedback here.

Pic #1: rusted metal cut out

Pic #2: Patched metal

Pic #3: Rust destroyer

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Weld penetration isn't so much about the wire thickness, it's more about the power setting on the welder. 025" wire is best for auto body stuff, you can weld thinner stuff with it without burning through. Using 035 requires more heat to melt it in properly, so burn through is more likely to be an issue. If you feel you aren't getting enough pentration either inch back the wire feed slightly or up the power a bit. Tack the edges of the repair section in every 2 inches or so to start with, then add short welds in between each tack, and repeat until you have it seam-welded. Doing small bits at a time reduces heat build up and distortion and burn through. If you have to bridge a burn through area, drop the power one notch, up the wire feed so that it barely melts in and flick the trigger rapidly to give small quick bursts of wire. When you have the hole filled with what looks like bird droppings, correct your power/feed setting for normal welding and go over what you just did to smooth it out.

Oh, and practice on some scrap stuff, and experiment with turning the wire feed knob slowly while welding(NOT the power knob, you'll hurt the welder)and you will also get to recognize the sound of a good weld being laid down. I clean my areas to be welded with a bit of paint thinner to degrease it. Just make sure it's dry and the thinner is capped and well away before hitting the welder. Have a fire extinguisher at your elbow when welding. Enjoy! Welding is great fun when you get the hang of it.

Oh, and your car is worth doing, I have saved far worse machines from the crusher Here in Northern Ontario, rust is quite severe. Guys from down south wouldn't look twice at stuff we consider do-able up here.

I usually make a cereal box cardboard template before ever cutting any metal. It's so much easier to rough it in cardboard, then fine tune it with a pair of scissors. Then just trace your pattern onto metal and it will fit first time, no grinding req'd.

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I choose to be happy, even when the Mercedes is being awkward, lol

I'm doing the cereal box cardboard technique, but I still end up needing to do some grinding, especially if the patch is shaped. With my car, I figure I know everything about it already and it's good to learn how to do this type of repair in this climate because I'd have to end up doing it on any car I own.

As for the welding, I'm hesitant to go back to the .025" because I let it unwind some and now it jams. Such a pain in the ass. NEVER LET THE WIRE SPOOL UNWIND. I fooled around a bit with the settings and .035" with setting C-4 (wire feed is dialed, but heat is notched) like bob said seems to work pretty well. I'm gonna try that hole filling technique, that's a good idea.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition