Thanks a lot for all your valuable suggestions! 
Just to give more info on my situation.
To date I can't find any leak. The fans are working fine. So I
suspect could be a clog somewhere.
So far I use only water in my cooling system, and this has kept the
temperature at half or below at the temperature meter most of the
time, until this prob came up. Previously I had leaks before in the
pipes, and that was when the temperature shoots up. But I always
find the leak, which will be visible dripping somehow.
Currently the water coolant reservoir is drying up very quickly.
And the water is there is really like rust water.
The temperature remains close to overheating after drive and can
still drive without prob. After each 1 hr plus drive, I have to top
up my coolant reservoir with abt 1 litre of water. The water in the
radiator is still full leh...
One strange symptom is that when I stop to park, I found that the
water in the coolant reservoir is slowly overflowing out from its
tight cap, like forced out by heat. Then when I check later, its
like a lot of water is lost to evaporation.
I think I will not fix it, but top up water and use for another 2
weeks. I really dun want to fix it, becoz everytime your car prob
is fixed, you will love you car very much. I dun want to love my
car more and then sent it for scrap 
