Asus K501UB fan is very noisy

Hello, 

My K501UB is very noisy, it always running at 4000rpm or higher. I don't know what to do. It really drives me crazy and cannot focus to work. 

I have tried to use hwinfo64 to config my fan but there was not any information about fan speed. Does anyone know why? 

By the way, I know I need to add the hwinfomonitor but I cannot because each time I launch the program then it crashed, something likw HWMonitor has stopped working.

Thanks.