Ground controllers confirmed the installation went well and the pump is receiving power. They then filled it with ammonia which is used to keep the International Space Station cool.
The original ammonia coolant pump failed July 31. As a result, ground controllers were forced to power down several of the station's functions.
The spare ammonia pump installed Monday was delivered by space shuttle Discovery and stowed on an external stowage platform in July 2006.
NASA said Monday's spacewalk took 7 hours and 20 minutes. The first repair spacewalk took place Aug. 7 and lasted 8 hours and 3 minutes, making it the longest International Space Station-based spacewalk and the sixth longest spacewalk in history.
The second one took place last Wednesday and took 7 hours and 26 minutes.