WOW, haven't seen rust like that since my 1952 Ford Zephyr!

Problem was poor metal prep in the factory. There's even rust under the paint that hasn't bubbled. Must be one that was hanging between the acid treat and the primer vat all weekend!

Cleaned it up, tapped it HARD. bit of Tremclad and I think we're good 2 go.

I'm still shocked sometimes by the mistakes that MB can make - still.... LOVE my 400E (Needs gas - it's mine again for a couple of hours!!)