Before replacement do the following things,Then also problem not solved then you can change the fan.
1. Start by Cleaning Your Computer's Fans
It'll probably take around 30 minutes to clean all the fans in your computer, maybe less if you have a laptop or tablet, and more if you're using a desktop.
Clean the power supply fan and any case fans. Canned air works great here, too.
2. Keep Your Computer From Getting So Hot in the First Place
In other words, your computer is very hot and, even with great fans running at full speed, they can't cool your hardware down enough to slow down—thus the noise!
3. Check Task Manager for Hungry Programs
Unless your fan-cooled hardware has a physical issue and is heating up and making your fan noisy for that reason, your operating system and software are the primary reason your hardware works more (i.e. gets hotter).
In Windows, Task Manager is the tool that lets you see how individual programs are using your computer's hardware, most importantly the CPU. Here's how:
1. Open Task Manager. The Ctrl+Shift+Esc keyboard shortcut combo is the quickest way there but the link has some other methods, too.
2. Tap or click on the Processes tab. If you don't see it, try the More details link at the bottom of Task Manager.
3. Once on the Processes tab, tap or click the CPU column so the programs using most of the CPU's capacity are listed first.
4. Typically, if an individual program is "out of control" the CPU percentage will be very high—at or close to 100%. Programs listed in the single digits, even up to 25% or more, typically are not a concern.
5. If a particular process seems to be driving CPU usage through the roof, which will almost always also be reflected as serious computer fan activity, that program or process may need to be repaired.
Hope this will definitely helps you..