Sixto described how to drain all of your cooling system...
 

... now when refilling, you want to make sure no air bubbles form. So, to avoid this, remove this bleed screw (14mm) shown in pic before starting to refill with your Valvoline MaxLife (should be OK). When the antifreeze begins to overflow from this hole,(on my 91 300E, after about a gallon and half) put screw back in and fill until plastic expansion tank (one with radiator cap on it) is about half full. Voila! You're done.

http://www.members.aol.com/buckweeat/bleed.jpg

Good luck!

~Paul

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'91 300E, 212K miles

Your car has a drain plug in the FRONT of the radiator and it might actually be accessible. In many cases, it's easiest to drain the radiator by simply removing the hose that's connected to the bottom corner(passenger) side of the radiator. This hose is about 1.25 to 1.50 in. in dia.

Lots of good info in front of this post(Sixto-Pmizell)