Lenovo THINKCENTRE 4485 - Manual (Page 148)

4. Follow this sequence to remove the four screws that secure the heat sink and fan assembly to the
system board:
a. Partially remove screw 1 , then fully remove screw 2 , and then fully remove screw 1 .
b. Partially remove screw 3 , then fully remove screw 4 , and then fully remove screw 3 .
Note: Carefully remove the four screws from the system board to avoid any possible damage to the
system board. The four screws cannot be removed from the heat sink and fan assembly.
Figure 77. Screws that secure the heat sink and fan assembly
5. Lift the heat sink and fan assembly with the fan duct off the system board.
Notes:
a. You might have to gently twist the heat sink and fan assembly to free it from the microprocessor.
b. When handling the heat sink and fan assembly, do not touch the thermal grease on the bottom
of the heat sink and fan assembly.
140 ThinkCentre Hardware Maintenance Manual