My ps3 40 gb makes this loud noise sounds like the fan

May be...

i played bad company for like the whole day ,then every 10 minutes after i turn my ps3 on it makes this loud fann sound??

It's not overheating, it's just getting warm. You do need 4 inches of ventilation on all sides, and don't keep your PS3 on carpet (sony site said so). If it was overheating, then a system message would alert you and the power light will flash red

Yeah mine does that too, its just over heating. just make sure its getting enough ventilation, and try not to use it so much.

It is probably the PS3's high-tech fan system, so they system stays cool.

the ps3 faning area is on the right side so make sure you lay it flat and that should take care of it