Distilled or Regular Water

After getting my new motor and cooling system up and running with reverse osmosis water and quality green coolant, I was getting these odd whitish soft gooey deposits everywhere I could see inside the cap opening. It would happen in just a few days.

I ended up using the anode attached to the radiator cap. It stopped all the strange electrolysis stuff going on and It didn't even consume the anode. Once installed it began coating just the electrode with this weird white gooey stuff. I wiped it off a time or two, and now it stays clean inside my system. I haven't had the problem since.

I also use those PH test strips for coolant strips from time to time test the coolant and keep an eye on things.