UPDATE 2-Spacewalking repairmen replace space station's leaky pump
* Initial tests show new pump working
* Coolant needed for station's solar-power electrical system
* Three crewmembers due to leave station on Monday (Updates with repair completed, adds quotes, changes dateline from Miami)
By Irene Klotz
CAPE CANAVERAL, Fla., May 11 (Reuters) - A pair of spacewalking astronauts wrapped up a hastily planned repair job on Saturday to replace a suspect coolant pump needed to keep the International Space Station at full power.
NASA astronauts Chris Cassidy and Tom Marshburn put on spacesuits and left the space station's airlock shortly before 9 a.m. EDT (1300 GMT) to attempt to stem an ammonia coolant leak that cropped up on Thursday.
Over the next four hours, they installed a spare pump, then positioned themselves to check for signs of escaping ammonia ice crystals when the system was turned back on.
"No flakes," Cassidy reported to flight controllers at the Johnson Space Center in Houston.
Engineers will monitor the system over the next several days and beyond to make sure the pump replacement fixed the problem. Continued...