[s-cars] chocolate grease in coolant expansion tank

[brian hoeft]

okay guys, so, to my horror while routinely checking for anything 
disturbingly obvious with my baby, i got cracked in the jaw.

why is my expansion tank black, oh f---!... take off the cap, swirl my 
fingers around and pull out fingerfulls of a black geasy substance.

my first thought was cracked head/headgasket, terminal illness, my lifes 
over, time to start donating various bodily fluids yadyada.

then after calming down, i thought, maybe the coolant/antifreze congealed in 
a way i wasnt aware of.

i think i made the mistake of adding  water wetter to the existing, 
distilled/blue(g-11?) mix.

is running water wetter, with the standard coolant&distilled water 
unacceptable?

my intent now is to purge the system.

is anyone familiar with a power purging system.. i dont know the name of the 
machine, but my friend has one and uses it for business.  i would imagine 
that it would remove contaminants better due to its vacum-like abilities, 
but maybe there are some naysayers with good reason to just buy a dozen or 
so gallons of distilled water and flush&fill until clear.

id appreciate any helpful words, brian