Check out my gallery and look at the NW's intake manifolds (w/ the green sludge) I bought these used, some time ago. This happened to the previous owner, not me. My guess would be 1.) No catch can. and 2.) internal IC leak and sucking coolant into the mani's. He probably had no puddle on the floor to see. I'm with going w/ the small reservoir for monitoring, and is what I will be doing. I'm pretty sure Tunaglove did a writeup on this.