This is for the new-to-me 190d. I noticed the coolant in the reservoir is slightly oily (slimy), is rust colored and has a grainy (almost sandlike) stuff in it.

I can only guess that this is rust but from where? Isn't the block and head aluminum on these motors? Perhaps the radiator is rusted inside?

The car came with no maintenance records so I have no idea how old the coolant is.

What do you gurus suggest on how to fix this?

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Ben
1987 190d 2.5Turbo