Engine coolant level '97 E300
 

My '97 E300 has a black opaque coolant expansion reservoir. How the heck are you supposed to know the proper fill level? :confused: My diesel VW has a clear reservoir where you can check the fill level against a marking on the side.

History: I have a slow leak somewhere. Every four weeks or so, I get the "low coolant level" message on the dashboard display, at which time I've been adding some distilled water to fill the reservoir to about half way full. Next time I'm under the car, I'll look for leaks and do a full coolant flush once I find the problem. But in the mean time, I need to know how full to full it!

TIA!!

there is a little plastic tab protruding from the side of the tank inside, that is the full mark indicator.