You could have an overflow bottle under the front wing at the rear of front wheel arch liner. Now please let us know if this is the M103 lump? . The W124 had this bottle but i am not sure about your 190e . If you put to much coolant in it will exit in to this bottle we talk about under the wing . The coolant should only be up to the join in the expansion bottle on the inner wing , thats when thev engine is cold . My bottle is under drivers wing in the UK .Yours could well be under same place but passengers side wing
Another place it leaks from is the rear lifting eye on the rhight hand side- at the back of the engine. Heater hoses come out of this the pipe thats fixed to the lifting eye that exits the engine and goes to the heater matrix . I will post a picture of the part it will need an O ring fitting on the end after its removed from the head . You will see if it is that leaking , by puting your hand down the rear of the engine to the place your cylinder head joins the block .It will be wet with coolant .It then runns down the bell housing and down on to the floor passengers side .Let us know if you find it .