I've found W203 motors complete, as cheap as $1000.00. I think that is overcharging. $2500.00 used? Likely they won't test it before they charge your pal for the labor and shop supplies and he'll be SOL if he can't get any guarantees.

eBay as a last resort provided with a video of it running before removal. Craigslist first. C240s can be had for pennies. I see a lot of rusty W203 [early production years] and ones with trans problems dirt cheap no one wants to fix on craigslist so keep an eye out for hammy down parts cars.

IIRC, you can't buy replacement engine parts either so that is out of the book.

Also is it a 4Matic? 4Matic was cosmetically identical to a 2WD, but a whole different animal inside.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k