I also checked with couple different body shops (not Mercedes) and they told me that this is the common problem with most of the Sprinters. Rusting from inside out. "Stone chips " from driving on highways usually hit the cars sideways leaving, maybe, scratches. Mercedes knows about the rust issues but they don't want to deal with ,giving people fabricated reasons "exterior influence ". They don't want to take the responsibility for their crap . Shame
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Sprinter don't die from rusting.
Paint chips caused by stones don't cause 'rusting from inside out' verbatim. Also, you may have tiny metal dust that has gotten into the paint and these start the process too.
Chips that expose the metal cause rust to form. The rust spreads under the paint. This rust is on the surface of the metal.
Here is what you need to do...
...purchase a quality automotive acrylic enamel single-stage paint that matches your colour. Using a dremel tool grind off all the paint and rust. Apply 2-3 coats of paint. Go watch some Netfix.
Lastly, each springtime inspect the van for paint chips and do the touch-ups. Any other time you notice the 'spider-webs' forming do the same.
My 11 year old van has ~30-40 of these repairs and some originating 7-8 years ago. None have ever reformed rust.
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