I just changed the transmission fluid on my friend's 98 ML320. I could not remove the pan drain plug. It was frozen solid with rust. I believe the dissimilar metals (copper/steel) exacerbated the situation. This was the first fluid change since the vehicle was new 13 years ago.

Of course it's not because of this.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.