HP Xw9400 - Workstation - 16 GB RAM Reference Manual page 124

4. Before lifting the heatsink, carefully break the thermal compound between the CPU heatsink and
processor by moving the heatsink back and forth or twisting it (3).
Figure 5-70
5. Use alcohol and a soft cloth to clean all of the thermal interface material residue from the CPU
heatsink and processor.
CAUTION:
114 Chapter 5 Removal and replacement procedures
Removing the CPU heatsink from the system board
Allow the alcohol on the processor and CPU heatsink to dry completely.
ENWW