To check for calcium deposits, look for white deposits inside the radiator, or on the metal surfaces when you remove the thermostat. Since the MB design has no radiator cap, this may be difficult.

I'm not familiar with the water down where you live. You may have lucked out and have good water that leaves few deposits.

You may have to do multiple flushes before you get the level of oil in the cooling system down to something managable.

I'm not sure of the name for that part, intercooler sounds about right. I don't have this feature in my model.

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95 E320 Cabriolet, 169K