Tips:
The late M119 blocks have drains which allow connecting a hose, so you can drain the block & radiator without spilling any used coolant. Loosen the plug very slightly, then attach a section of drain hose (the clear vinyl stuff from Lowes or Home Depot works fine), and turn the hose to open the drain. After fully draining the radiator & block, run a garden hose into the system when cold (at upper radiator hose and/or plastic tank) with all 3 drains open, to flush out residual coolant. If you're really anal you can do the same with the heater hose near the brake booster, to flush the heater core too. Let everything drain completely, close up the drains, and re-fill.
You'll find it's often easier to fill the block via the upper radiator hose then quickly connect the hose to the radiator. Having a second person assist helps greatly. With an empty system, it should take 5 quarts into the block via the upper hose, then another 4-5 quarts into the reservoir, and possibly 0.5-1.0 quarts more after the engine reaches operating temp and 'burps' the system. System capacity is about 12 quarts total,
NOT 16 quarts as printed in all the manuals. For a 50/50 mix you'll use about 6 quarts of antifreeze. I've experimented with many .034/.036 coolant changes and found the hydrometer indicates 50/50 mix with 6 quarts a/f, and 33/67 mix with 4 quarts of a/f, which confirms a total capacity of ~12 quarts.
EDIT: The TDM (Technical Data Manual) correctly shows 034/036 system capacity of 12.5 liters.
I would recommend pre-mixing the antifreeze with distilled water (or, non-softened tap water) and pour the pre-mix in, rather than putting in "X" quarts of antifreeze and topping off with water. If you don't pour in at
least 8-9 quarts, DO NOT start the engine yet, the system is not properly filled. Fill the reservoir all the way to the top, when the level stops going down (after waiting 5+ minutes), put the cap on & start the engine. Watch the temp gauge closely, if it starts climbing to 100C, there is likely an air pocket in the system.
You may find it difficult to dispose of the drained coolant. Find your local hazardous materials collection site, which is usually free. Relatively few auto parts stores will accept used coolant, which is odd considering almost all of them take used oil. Please don't pour it on the ground or down storm sewers, and remember that coolant will kill any animals which drink it, so do not leave puddles of coolant under the car.
The coolant change process is so much fun, you'll likely end up stretching your next change interval to the 5-year/50kmi max allowed on the label of the G-05 bottle.
EDIT: Skip to post #77 in this thread for more information about extending the change interval.
Finally - if you replace the plastic reservoir, also replace the sensor, and get the OE (or OEM Hella) sensor only ($20-$25). Also replace the cap as well, they are cheap for OE (OEM Reutter) at ~$5/ea.
EDIT: The plastic reservoir is NLA from Mercedes as of approximately summer 2024. MBCC link here.
