I've got an 87 SDL and in many ways its nothing like your CE and your symptoms sound nothing like anything I've experienced,but. I recently had an episode of smelling coolant immediately after shut down. To make a long story shorter I ripped out my center console, half my dash and I was going to start on the heater box when I luckily got side tracked.
I found that there was an engine coolant, heated unit that spans the width of the windshield and extends a couple of inches upward and undrneath from the windshield bottom edge, its supposed to melt ice and snow accumulating there. In my car this unit had sprung a small leak. What happens is that the coolant was leaking into a drainage bay just below the bottom edge of the windshield where the wiper motor and transmission is located on the drivers side. On the passenger side under the dash in this area is the climate control blower motor and the fresh air inlet! So when this leak occured coolant was being sprayed and dripping within inches of the fresh air intake and its' smell drawn into the passenger cabin. On my SDL you can access the area by pulling the wiper arms off (undo the 13MM nut) and pulling off a foam seal strip and five metal clips to remove the plastic grating covering this area.
I don't know if this has anything to do with your problems or particularly the coolant smell issue but I was suprised by my discovery and maybe it will help you discover something interesting about your Benz, Good Luck!