The astronauts and cosmonauts aboard the International Space Station used a pair of robotic arms Sunday to install equipment ahead of Monday's spacewalk.
Crew members Dave Wolf and Tom Marshburn configured their space suits and tools, and reviewed procedures for further construction work.
But crew members found their efforts were hampered when one of the space station's two toilets malfunctioned. As a result, crew members of the space shuttle Endeavour are restricted to using the shuttle's sole commode.
Officials with the U.S. space agency, NASA, said the problem is not a big one, but could become serious if the toilet remains out of commission for more than a few days.
Astronauts completed the first spacewalk of their mission during a 5.5-hour operation at the space station Saturday.
Wolf and newcomer Tim Kopra floated out of the hatch Saturday to help install an external platform on the massive Japanese lab at the space station.
The platform will allow scientists to conduct experiments in the vacuum of space.
Five spacewalks are planned during Endeavour's 11-day mission.
With the shuttle crew's arrival, there are 13 astronauts aboard the orbital station - more than ever before.
Kopra is taking the place of Japan's Koichi Wakata, who has been on the space station since March.
Some information for this report was provided by AFP, AP and Reuters.