Quote Originally Posted by chrshaha View Post
mas mabilis po ba talaga mag evaporate ang distilled water? chine check ko po kasi yung kotse, baguhan kasi ako nabili ko po ng second hand and last time naubusan ako ng coolant bigla. triny ko palitan ng radiator cap parang hindi naman na gaano na babawasan compared as before. siguro third of a cup po ang bawas ngayon pag ginagamit, dahil sa evaporation kaya yun or may leak?
in the olden days, when car engines were made up of iron, ordinary water was fine.
in today's aluminum alloy engines, "coolant" has taken on new meaning. consult your car manual, po. "pula" o "verde" are the two popular ones.

it is difficult to explain coolant loss and how to determine its existence in the modern car to a, pardon me, "total newbie".
"a third of a cup" loss, as determined by the opening of the radiator cap and adding more water to spillover, is not a significant loss, in my opinion. it can be easily explained by the engine's normal running cycle.
instead, i look at the radiator overflow cannister's low and high marks, to see where my coolant levels are. a good flashlight helps in finding these marks. so what does your cannister level show?

so what is your car's make, year and model, etc etc?
if it has a real temperature gauge... well, i prefer my cars to have one. i believe i can spot overheating, early on.

if you have your car's owner's manual, reading it will greatly aid in your understanding of the car.