Lenovo ThinkCentre A57e Hardware Maintenance Manual page 104

3. The rear fan assembly is mounted with four rubber mounts that protrude
4. Install the new rear fan assembly by aligning the rubber mounts of the system
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Hardware Maintenance Manual
through the rear of the chassis. Remove the fan assembly by pulling the rubber
mounts back through the chassis.
fan assembly with the holes on the chassis and push the rubber mounts
through the holes.