The block drain is a giant bleed nipple just like on a brake caliper.
It is on the left (driver's) side of the block directly above the motor
mount arm.
I think it is a 6mm allen inside to loosen.
DR.D

__________________
Dr.Diesel -
Shop Foreman
Master Guild Mercedes-Benz Technician.

Think the dealer is expensive? Do you know how much it costs to train a dealer tech? Or buy the required MB special tools to have on hand?