I just got my first mercedes about a month ago a 83 300sd. I knew I needed to learn a few things about these cars but found another site before I found this one. I was reading a post on cooling where a gentleman claimed 100 C was far too hot to run the engine. At the time I wasn't worried but as the air temps went up I felt the need to us my air conditioning. The first time I used it temp shot to over 100 C. Then I discovered the previous owner had the wrong coolant in the system so I flushed and filled, put a new t-stat in and 1 bottle of water wetter. Today air temp was 85 F I was running down the e-way at 85 with the air on and the temp hung around 95-98 C. Without the air on I ran anywhere from 85-90 C In my other vehicles I notice no increase in temp with the ac on. Is this normal for the benz? How much water wetter can you put in the system? I would like to run her as cool as possible and am worried when air temps go higher so will my coolant temp. I normally don't run it at 85 mph and stay right around 65- 75 0n the freeway. Any thoughts would be appreciated.


Jim