I recently took my SDL on a road trip in 110˚F weather (43˚C for you Metric types) and my engine temp fluctuated between 90-105˚C depending on what type of hill I was pulling up. It normally runs dead-center of the temp gauge at 85˚ in anything under 105˚ outside.

One thing that helped immensely was cleaning out the A/C condenser. Buy some of the foaming coil cleaner and clean it WELL, then wash everything out with a high pressure hose. Repeat 2-3 times. You'd be surprised what comes out...

If that doesn't help, check your fan clutch. In that kind of weather, you should clearly hear the engine driven fan roaring under the hood as you drive around. If the condenser is blocked or if the clutch is bad, it'll be freewheeling instead of moving air like it's supposed to.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]