Yes, unfortunately, your experience is what the rest of us experience, too. If you have already done the obvious maintenance, like clean out between the A/C condensor and radiator, and checked to be sure that the auxilary fan(s) comes on correctly, de-scaling (cleaning out) the inside of the radiator and maybe adding a wetting solution is all that's left to try.

As a long-time MB owner and fan, it pains me when MB does things that seem so obviously inferior, and engine cooling is right at the top of the list, along with anemic A/C systems, but they are what they are.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't