for cleaning just normal water (boil it first if possible) and shake the rad / res etc. but dont put it inside when its too hot (you already know why
for the coolant you can make your own using distiled water, being more especifc the demineralized one (yes i found distiled ones with minerals and that dont work, i didnt even knew that it existed
some pt_nuke (biocide) to kill algae ~ just one or two drops will work per liter of water.
note that distiled water is all you will need, since it is non condutive (it wont get your mobo fried if leaks ~ just a small leak though lol)
also you can add dyes to get some cool colors, but i dont like them, someday they will make the tubbing colored (if it was clear) and the own coolant you made will loose color with time and when you open your block it will be all there
small edit -- this is distiled water
but for its price you can go to an automobile store and get some liters at same price maybe.
link for pt_nuke