w210 coolant drain question
 

I drained almost exactley 2 gallons of coolant from my 210 this morning from the radiator only not the block drain. When I was refilling only 1 gallon went back in. I started the car and let the engine warm thinking that I could add some more when it got to operational temp. It very quickley went over 100C. At this point I shut it off thinking that there is an air bubble somewhere. I felt fluid in the lower hose but the upper hose was completely empty. I disconnected the top radiator hose and filled it until I culd no longer. It took an additional .5 gallons. The car is still running much hotter than normal.

What did I do wrong?

I used MB fluid and 1 bottle of WaterWetter.