Check if the fan is bolted to a round alluminium part that is bolted to the water pump. If so try to spin the fan with out the motor running it should spin smoothly with a little bit of resistance. If it doesnt move or feels rough the free wheeling bearing is seized or the internals of the coupling has failed. To be 100% sure remove or loosen the fan belt off & start the motor & see if the noise goes away if so get a new coupling.
Rogue.
This bloke has a real problem & he sounds a bit stuck with it. So if you cant help him keep your dumb comments to yourself.
Coops.

oh.. thanks COUP1200
the fan does bolt into an aluminium thing and to the water pump..
later i try to spin it and see..
so if it is rough means i have to take it to the mech already...

ocphangaz : nowadays weather here getting hotter and hotter, even if i drive at afternoon, the water temp will goes up to the middle mark also.. :) and mostly stay there

last time it used to stay constant at the 2nd mark..

did you convert your rad when you change to A15? i'm using vanette rad with 2 rows of holes...

also you can try to flush your rad.. after all these years the rad must be filled with gunk!

also the fan mustn't be too smooth when engine is idle... this will cause the fan not able to pull enough air

oh.. i not change the radiator...
i thought the original one is enough.. :)

cause the fan is big and radiator fin area also big (bigger then modern car.. :) )

it is big.. but not necessary as efficient as the newer car's rad.

furthurmore, newer fuel injection cars need to have the engine at certain temp to have maximum fuel burning efficiency.

but on carburetor cars. it is best to have the engine temp as minimal as possible (slightly more than 40C) so that the fuel can burn properly...

tried running the engine in the hot afternoon while in a massive traffic jam? the engine rev will slowly drop and the engine will start to loose power.