My cousin is pulling apart his 1998 Forester which yesterday started dumping major ammounts of fluids FAST (Water pump/headgasket) The question that I have is this....When they opened the radiator cap after it got towed home, there was this strange blue/brown substance coming out of the top. Any ideas? I've certainly never seen anything like this before? Is there something else he should be looking at in conjunction with or instead of the regular suspects?

Brown/black stuff if most likely oil in the coolant. The other may be headgasket/coolant leak fix material.

 

Make sure he gets the radiator cleaned and tested. I'd recommend changing all the hoses as well and flush the heater core well.

what he said - oil coolant mixing most likely. check under oil cap too for unusually colored mixing in the oil as well.