It's summer and outside temperatures are up to 105F +.

Probably, it is normal the way the 300SD runs, but since I am going out to the desert in a couple of days, I wanted to make sure I check everything.

I replaced the thermostate it has a 80C now. There was a 75C in it. Temp gauge shows the same, close to 90C in this kind of heat. Yesterday, the aux fan came on, which is really rare.
(I suppose the mark between 80C and the top white mark next to the red one <120C>, indicates 90C)

I am wondering, because I also replaced the thermostate in the 300D (80C) and it stays right on the 80C mark under the same driving and outside temp circumstances.

What else should I look for? I know there are a lot of elements throughout the cooling system, but what would be an obvious catch. Coolant level is up fan clutch seems ok, no belts slipping.

I should mention the 300D (also turbo) has no A/C belt. I have no need for it in that car. But, I never run the A/C in the 300SD

Else, maybe I should have the radiator checked...?

However, temperature is steady and no overheating so far, just a bit warmer than usual, when the outside temps are cooler it also runs cooler, unless I go uphill, in which case it will go up to the same level. But here I am not too surprised since the 300SD body is prolly heavier than the W123.

Any suggestions?

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