[s-cars] Gelling coolant

[Gísli Óttarsson]

I have noticed that the coolant in the expansion tank has a strange texture
to it.  It is almost like it is beginning to gel.

Any ideas what the story might be?  Can this be due to some kind of a mixing
of incompatible coolants and all I need is a complete flush, or is this
something else, possibly worse.  Is there anything I should do or some test
I should run before I pull the trigger on the flush?

Ideas?

  Gisli,  ('01 S8)