Did you ever find out the problem? That 'brown snot like stuff' was in my car, it was the coolant! That DexCool crap, turns to that brown junk, and clogs everything up! Get it out of your car!!
I had to get my engine/coolant system flushed out 4 times, to get it all out of my car,and replaced it with Peak Global lifetime Coolant. Luckily it was just starting, so I didnt have any problems, i had heard that Dex Cool was known as 'Dex Kill', because it turns into this brown crap and clogs things up, and ruins the system. Was this your solution, or did something else fix it? All I know is my 2006 Aveo Automatic, with very low miles, around 15K at the time, had this crap in it already, and if you go onto YouTube, you can see videos of this brown junk in many Chevy cars/trucks. I'd like to know if it was your problem as well, or what was the problem???