I'm wondering if J-B Weld would be o.k. to use in filling in holes that have rusted through. I have several areas inside my trunk seal tray on my 86 SL. I'm not a welder and thought it would be better than Bondo. Thanks.

Rust is a gremlin. There is much more than meets the eye. Down in FL. I would not hesitate to scrape all of the affected area and use the POR15 method of rust treatment. It works well. If you catch the rust soon enough you will be ok.
So scrape all affected areas down to almost clean metal. Then clean with Marine Clean, then the Phosphorus Acid rust treatment/ metal etcher from POR15, then the POR15 rust treatment paint. Then use bondo or fiberglass filler to fill the holes.
If you have to scrape rust from visible areas it will be better in the long run. You can always repaint later. Fixing the rust should be a priority.

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Chris
84 280sl
82 300d euro

Thanks for the reply. I've used POR-15 before and it does work well.

JB ( epoxy ) is too brittle and $.

A wire brush and rustolem works wonders to slow rust. If the holes are of the pinhole size, use DAP brand Dynaflex 230 . This is an elastomer ( non silicone rubber ) sealer very similar to body seam sealer even though the label says not for automotive use. I use it for sealing seams and sealing rust patches.

Most home centers stock caulking tubes of the stuff, it can be had in clear, white, aluminum, brown, black and maybe another color.

I've battled rust for 40 years. It's not worth repairing if you plan on continued winter duty for your vehicle. The only thing that can slow it down is a good coating of rustproofing.

It's too late now, but your efforts are better directed toward prevention. I learned that lesson early on.

Sometimes you have to fight the battle...

I just wrapped up some rust repairs to my W124 sunroof opening and I can say that if you love your baby, catch the rust early and address it properly based on your skills, materials at hand and location as well as your desire to tear into it.

At a minimum, scrap, sand and remove as much rust as you can, treat with a rust converter or wash, encapsulate with POR or similar, and then reconstruct the area as best as you can with JB Weld.

JB Weld is very strong, easy to work with and its epoxy based properties makes it ideal for rust repair as it also adds a very hard encapsulation layer to the repair. I have used JB Weld for years in numerous capacities, for reconstruction of rust damaged areas such as battery trays etc. Should work well on your SL trunk floor. The key will be to mix it or work with it when it is thicker so it wont run on you. Also feel free to use screen, fiber mesh or whatnot to strengthen larger areas.

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

I can second that! a good Rustproofing is worth its weight in gold, especially if you want to keep your ride for decades.

Up here in the salt belt, rust proofing is a normal yearly ritual for many of us. Even my cars that are solely a summer sled, they get the annual rust proofing treatment. Some of my cars I only drive at most 2000km a year, and I still coat them before storage. Rain water sitting inside door seams can still cause rust.

Ive actually got to the point last year that I didn't trust the "thoroughness" that the coating places do. So I built my own pressurized rust coating spray system, and its been working great!. And I can run both types of fluid thru it. And it gives me more 1 on 1 time with my cars

I can honestly say that I was able to 100% stop rust in one situation, I had a small rust bubble spreading from one corner behind a window edge. Going thru a automated carwash, popped the top of the paint flake off and exposed the rust. I soaked it in rustcheck fluid, to give me some extra time to get some matched paint (its a custom color) before I could refinish it. Its been 5 years since that has happen, I still haven't gotten the paint yet. But the rust spot hasn't grown at all

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Just my MB's:
1990 420sel - Winter DD - 410,000km
1990 560sel - absolutely showroom mint - 360,000km!