If I were to remove and replace the entire rocker panel from each side of my W124, would I need to brace the chassi while doing so? I have had to remove each end of the rockers completely because of the rust, but the middle portions are fine. I had considered, for ease and possible structural integrity, removing and replacing the entire panel, which would consist of about 100 spot welds drilled out and plug welded in. It's crossed my mind this is a structural element and might be an issue to remove the whole thing without bracing the car. The floorboards will stay in place and are fine, other than one small rusted area I will patch (about 2X10 inches).
Hopefully it's not an issue that I already drilled out the front areas of the rocker and a small area at the bottom of the A pillar ... the rust was so bad.



Note that the inside of the frame (which is part of the floorboard, stays intact. If I removed the rest of the rocker that would still be the case. There are spot welds along the pinch between that and the rocker that would be drilled out.



So I'm debating whether to remove the entire length of the panel, and how much that would complicate things, or whether I should just butt weld it onto what's pictured above, with plug welds holding the forward part of it.

__________________
1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

General rule would be to work on one corner at a time. The corner connects two or more structural elements so not stressing anything while you're doing that is best.

Are you going to weld the jack hole and its support to the existing remaining rocker structure and then the outermost exterior skin over that? Or are you sort of scabbing a complete replacement jack hole/rocker section into the space you've got? Have you figured out a way to get some rust deterrent into that area after it's welded back up?

Pretty ambitious surgery there.

The jack port and bracket are actually part of the outer skin. I can post a photo later. All of it was held on by spot welds which I drilled out. So the piece I'll put back in will be a self-contained part aside from the one butt weld along the vertical cut down the rocker. And the little bit of a pillar that will go over the top. I believe this is how the repair was intended to be done based on the panels originally available from Mercedes. They sell that little bit of pillar which suggests to me the way it was done was removing and replacing the entire rocker via the factory spot welds, and in order to do that the small portion at the bottom of the a, b and c pillars had to be cut off and replaced over the new rocker. Unfortunately I really don't know what I'm doing and it is ambitious but I didn't have much choice but try and do the best I can. The only examples I could find online were partial repairs to patch up rust directly around the jack port. Mine were pretty far gone and I wanted all the rust gone. If I can find the chunks of rocker i need though, it's not a whole lot of difficult welding to put it back on and will be almost exactly like it was from factory. I think it will be a good repair ultimately, I just need to make sure I support the car where necessary when taking apart )or just do one bit at a time like I've done above).
For rust proofing,I plan to use weld through primer where I can, and spray cavity wax where I can't get anything else. There are several access holes in the rockers for this purpose. I'll also use seam sealer along every lap or pinch weld of course.

__________________
1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

I just finished this job on my Jeep Grand Cherokee (unibody). It's doable, just go slow.

Argon makes the welding very neat &tidy, but only on downhill shots(you can't make argon float...)

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Here is a link that has photos of the complete rocker panel as it comes from MB. MB W124 E-Class Rocker panel- Center Pillar - Ersatzteil-Ossi I actually found out from the classic center that these are still available. So if I can put the whole thing in, I'd rather do that ... my thinking is that the closer to factory design I can get, the better.
This still leaves my concern of whether to brace the car. Googling rocker repair on unibody cars in general it seems they do need bracing, although I'm not sure if that's the case when I'm not removing the inner wall of the rocker. I have the doors out which is concerning, so maybe I need to brace across the door openings?
I might be overthinking it, but I would much rather overthink it than finish it and find out I can't get the doors back on because the whole car shifted.

Simpler=better, when you did your Jeep, did you use any bracing? What was your procedure? I'm not massively worried about the welding itself as I think I can do a good job with patience. But the preparation I'm more worried.

__________________
1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

How did this repair go? Did you end up replacing the entire rocker panel with factory? Thanks.