Last summer I ran redline water wetter and distilled water on my N/A KA24DE. The water in the rad turned pink (redline is red) so it looked fine.
When winter came I drained it out, and put in a 50/50 mix of the green stuff, antifreeze that is. Boosted the car over winter.
Come spring, I drained it and replaced it with tap water. As I had to replace a radiator hose. The water still had a green tint from the left over antifreeze sitting in the cooling system.
Yesterday I drain the system again, install a new water pump, and run Gunk 10 Min. Radiator flush with tap water. Drained it out, and filled and rinsed the system twice with tap water.
Today I filled the system with de-ionized distilled water from the auto store along with a bottle of Redline Water Wetter. Drove around for about 30KM, came home to check the water level, and the water was all black. Not thick black, when I dabbed a white rag into it, the rag remained white. I thought maybe I blew a HG, so I checked the oil cap and dipstick and they were fine, compression checked and it was fine.
Anyone have a clue what may have happened? I'm guessing some sort of chemical reaction, but I am stumped on why it didn't turn black last year. My cooling system is very clean, new hoses, alum. rad a little over a year old, water jackets in the head are clean.