Just keep in mind that you should use the good stuff, 3M and SEM are good products. There are different grades of these too. Not cheap, but straightforward to use. Overlapped bright metal bonded with these adhesives is imo a better and stronger bet than fiberglass and por/miracle paint.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

Please, for the love of all that is, don't use adhesives for bonding the replacement panels. Don't use rivets either.

I've repaired this area recently. Here's the point in the thread where I got started in that area.

https://www.peachparts.com/shopforum/diesel-discussion/404186-w123-floor-rust-repair-8.html Starting at post #112

__________________
Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

Ahhh, almost identical to mine. Thank you in advance for pointing me to your thread.

To be honest, my preference is to weld and do it "right". I don't have a MIG welder (only flux wire which is said to suck for automotive work) and technology has come a long way.

I can at least prepare all the metal and patch pieces and call in a mobile welder to do the tack welds. This is the option I am leaning towards now but have lots of work to do before I decide which direction to go.

Flux core wire is too large. The smallest wire you can get in flux core is .03. .23 is much better for a beginner welder. Use 18g steel for patchwork. You can cut to fit and start your arc on the 18 with takes the initial bump of heat. Then wiggle your whip and let it flow onto the thinner metal.

If I had it to do over I'd buy a huge bottle of CO2/Argon and not fool around with flux core. Flux core is great for heavier metal, especially outside with the wind blowing.

If you're working on structural or the skin of the body you might want to find original panels which are rust free and always cut more from the donor than you can possibly use.

__________________
84 300SD
85 380SE
83 528e
95 318ic

Why not? Worked great for my repair job. This stuff is approved by OEMs. Some parts on cars come from the factory this way. It’s definite that it’s bonded and corrosion inhibited. Like using wood glue, the adhesive can be stronger than the metal itself.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

But you're not comparing apples to apples.

Adhesives can certainly be used for body components and very effectively. However, when they are used, those seams are engineered to be connected by adhesives. The bonding surfaces are specifically designed to be large enough and in the right orientation to be effective structural members in the vehicle.

Imagine something that is bolted together, like this pipe.



You can compare the adhesives to the bolts. Both need a surface area to communicate the load across the joint. Now compare that to a welded pipe.



Those pipes are designed differently than the flanged connected ones. Try to imagine gluing a pipe that was designed to be but welded, the connection would not be strong.

And in terms of using adhesives in our vehicles (like the w123), most of the areas they'd be used aren't designed for that type of joint. Welding replaces the metal and restores the strength of that section of the car to what it was designed to.

Add thermal expansion to the mix and adhesives are a really bad idea. Adhesives are going to expand and contract at a different rate than the metal its bonding which will weaken the bond over time. Welded metal joints aren't going to have that problem.

__________________
Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

I am referring to the area under the rear windows. In the coupe there are no rear doors.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I just bid and got a new 50 amp plasma cutter for ninety dollars American all in including delivery from China. Similar should be possible for a smaller gas mig.
It will not have a lot of quality. Yet can get tne job done. Consumables are peanuts in cost as well. For the plasma torch 15.00 delivered for thirty nozzle replacement parts. .

For the area under the rear side windows it may be possible to look down there with a cellphone borescope.

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Even if it lasts a few times, that's a good deal. I'll have to look into it as I need the equipment.

For the area underneath the battery tray, which is in close proximity to the dash and electricals underneath, any issues with taking the adhesive approach here and welding the rest?

Have attached 2 pictures, 1 of the area, and a 2nd picture 2 patches covering it (if I can use adhesive to stick them together). Any thoughts on this? (the cardboard is just an example and not my actual patches )

Attached Thumbnails

   

I use real 2-part epoxy (not the quick kind) and fiberglass matt on
things that are not structural or very visible. It can be thin or built up for strength.
Of course, any rust has to be removed and treated as standard prep.

Real epoxy does a great job of sealing and stopping any further rusting.
Practice helps - It can be messy if you do it wrong.
Uncured epoxy cleans up with alcohol.

__________________
1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI

So, the big benefit from using adhesives in this area is that it doesn't risk damaging the dash/electronics on the other side like welding would. The problem is that you're still going to have to access the back side of this panel to remove the rust and prepare the surface.

You aren't gaining anything by going for adhesives over welding if you still need to get to the access the rear by removing the dash.

__________________
Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

This is fascinating .

My 1959 Nash Metropolitan FHC had rusted out floor pans, not structural although they hold the seat mount studs .

Thirty years ago, before I bought the car the floors were glassed, I hope the prep work was done properly, they don't leak and are still strong three decades later ....

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Appreciate the tip!