radiator questions - Zerotohundred.com

i have a few questions regarding d normality of a radiator n how it works

- how does a radiator actually work
- is it normal for d spare tank to see a decrease in water level after some time eg few days after topping up
- i understand dat making d fan run on direct current will decrease d life of d fan motor. is there a way to maintain dis set-up @ d same time maintain d life of d fan

tq n ur expert opinions are very much appreciated

rgds

fazid