How does your oil look?
 

That coolant has the nasty look of neglect or you've got cross contamination issues. Any problems with the transmission or overheating? I can't help but think there may be oil or tranny fluid in your coolant, hard to tell from the pics but that doesn't look so good. Is it thick and goopy or not viscous at all? if it's chunky you need to consider the head gasket is going or gone. Take care of that, it's a sportline.

best of luck

I think the rad drain is in the front, pass side where you access the tow hook. Red cap. The overflow does feed into the wheel well behind the overflow tank and drains out there

What was the diagnosis?

MB recommends a coolant change every 30k, and i'd guess your car went a LOT longer than that in between.

Use the MB coolant, it is recommended, and after the flush and refill and pressure test, maybe a new thermostat/radiator cap would be a good investment, and make sure all the hoses are good, including the bypass hose.

Your car is the very desirable Sportline model, with uprated suspension and seats, not a run of the mill 190. The 2.6 motor puts out a robust 185 hp, so it's not the fastest ride in town and you won't smoke every "Type R" around, but it is very well balanced and handles extremely well,

AND, it is a very good looking car, so get out there and CLEAN THOSE DIRTY WHEELS and wash the car!!!

The 190 Revolution website is full of great information, and if you look in the website gallery for cars of the month, you can get a good idea of how stunning yours could look.

A Sportline 2.6 is about as good as you can get with the 190, except for the EVO Cossie.