Lenovo ThinkCentre 8111 Hardware Replacement Manual page 22

This section provides instructions on how to replace the microprocessor.
14
Hardware Replacement Guide
Important
Leave your computer turned off for at least one hour before removing the
microprocessor to allow the thermal interface between the microprocessor and
the heat sink time to cool down.
1. Open the computer cover. See "Opening the cover" on page 5.
2. Pivot the drive bay assembly upward to gain access to the system board.
3. Remove the heat sink 2 from the 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 system board.