First thing I would say is that the numbers on the readout are frequently not accurate. Perhaps the infrared thermometer will tell. If that is the case then you will know how far it is off. These problems can be real frustrating. I had an Isuzu Trooper that would overheat. Replaced everything except the radiator and still overheated (had to even replace cracked head) tried a flush product and no improvement. I ran a gallon of vinegar in the coolant for about 100 miles and then flushed it about 100 times (or so it seamed) till there was no odor of vinegar. Never overheated after that. Do not know if it would damage a MB cooling system. So follow the normal disclaimer, I cannot be held responsible... bla bla.

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Currently
1991 Mazda Miata 174000
1991 Subaru 189,000 Winter beater

got rid of:
1984 VW Vanagon 195,000
1976 350SE Euro 185,000 KM
1973 280SE 4.5 (boy do I regret that)
1980 280SE European W126 4 speed manual (miss it)
1989 BMW 735iL 119000 (good riddance)