It was there where you said and easy to get at since the starter is on the other side.
It has neat plug as I didn't have to take it out, just loosen a little and out came the coolant although not much. I drained the radiator first and that got most the coolant out.
Now I am having trouble refilling it. I can't get more than 1 1/2 gallon into it. I'm going to dp another post to ask how to fill. My 300SD 5 cyliner engined filled easily.
P E H