Step 1: First, remove the five screws with yellow dots in the figure below. There are rubber pads on the four screws in the middle. When you buckle them hard, they will fall off, so you can remove the CPU radiator.

Step 2: Remove the screw at the red dot in the figure below. Although the fan is loose at this time, it cannot be disassembled.

Step 3: The green position is the fan power supply, and the one behind it comes down.

Step 4: Then you can remove the screws on the fan and you can see the blades. Brush them well with a brush.