Lenovo ThinkCentre 3231 Hardware Maintenance Manual page 122

4. The front fan assembly is attached to the chassis by four rubber mounts.
Figure 29. Removing the front fan assembly
5. Install the new front fan assembly by aligning the new rubber mounts of the
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Hardware Maintenance Manual
Remove the front fan assembly by breaking or cutting the rubber mounts and
gently pulling the front fan assembly out of the chassis.
new front fan assembly with the holes on the chassis and push the rubber
mounts through the holes.
Note: The new front fan assembly you received will have four new rubber
mounts attached.