Changing the coolant in the W220 is really a straight forward service that will help your vehicle.

First and foremost, purchase the coolant that you need from your dealer. It will cost more, and many people will say that another brand will work just as well, but I can tell you from over 240,000 miles on one our C230's that the coolant system is like brand new. Also, purchase a new radiator cap from the dealer.

Second, raised the vehicle and let it rest on wheel ramps for safety.

Third, there is a drain valve on the driver side of the radiator. The handle is red and should turn easily. Gently open the valve and let it drain out in a bucket or catch basin.

Fourth, close the drain and open the overflow tank and fill up the system. Then let it drain again. Do this two or three times. DO NOT use a pressure system for cleaning the system and make sure the system is drained. Then close the valve and lower the car to the ground.

Fifth, purchase a large drink or juice container with a lid. I have one from RubberMaid with that is four liters. Pour half coolant and half distilled water in the container and shake it up.

Sixth, fill the coolant overflow tank with your new coolant mix. When you are sure that the system is filled, then start the engine and let it come to operating temperature and the thermostat is open. I usually have the heat set on high. Keep topping off the coolant tank, put the lid on and drive the vehicle.

The system self bleeds, so don't be surprised if there are one or two times that the coolant is low and you need to add more coolant. Enjoy the satisfaction of a job well done.

Use only distilled water (about a buck / gallon at the grocery store). Tap water contains minerals that will accelerate galvanic corrosion in the alloy engine and inside the radiator. (A radiator to transmission cooler leak is a really bad day, but described on the W210 forum more than you would expect.)

Use the distilled water to do the flush. Buy 5 gallons. Be sure to keep one aside for the final dilution with the MB antifreeze.

Buy and extra red radiator drain. They are $2 and nice to have as a contingency if the installed one breaks. (keeps you from being stuck midway with the radiator drained.