Lenovo ThinkCentre M55e - Manual (Page 19)

10. Remove the heat sink from the failing system board by pivoting the lever
1 securing the heat sink until it is fully in the up position. Carefully lift the
heat sink off of the failing system board.
Note: Place the heat sink on its side on a clean, flat surface so the thermal
grease on the bottom of the heat sink does not touch the surface and become
contaminated.
11. To remove the microprocessor from the failing system board, release the lever
1 securing the microprocessor 3 then pivot the microprocessor retainer 2
until it is fully open.
Chapter 2. Replacing hardware 11