the liana engine locks in air when you add coolant like an oaf - that needs to be bled out.. otherwise the coolant can boil -- bad bad thing..
Coolant is not that expensive - about 100 rs for a bottle, you car would take 4 litres of it at 30% concentration making the kharcha to be 150 for coolant and about 50 rs for distilled water, not that expensive - and it wont evaporate too. - peace of mind and everyday usage, is what a car is for - not opening the bonnet everyday
Another point, are you checking coolant/water by removing the radiator cap, the expansion tank is there for a reason, it also has 2 marks on it that say full and low - thats where you check the coolant level.
Anytime you open the radiator cap air can enter the system and lock inside