Spacewalk wrapping up with failed coolant pump still in place

Two spacewalkers are wrapping up a challenging spacewalk with inspections to ensure that their suits and equipment aren't contaminated by ammonia that leaked from a coolant hose.

Doug Wheelock and Tracy Caldwell Dyson were unable to remove a failed ammonia pump module from the International Space Station after one of the fluid lines became stuck and leaked ammonia crystals.

The pair removed three other coolant lines, but fell one short of being able to unbolt the pump module to open up space for a spare.

The module failed last Saturday, disabling half of the U.S. coolant system.

Wheelock and Caldwell Dyson will carefully inspect each other's suits and equipment for possible ammonia contamination, looking for waxy surfaces or unusual colors and contours.

They'll take time to bake off any ammonia in sunlight or with the help of heated tools, procedures that can be completed inside the Quest airlock.

Strict procedures are in place to ensure that the toxic chemical isn't returned inside the station's closed-loop environment, potentially poisoning the air.

Mission controllers want Wheelock to return there since the sensor monitoring his spacesuit's carbon dioxide levels has failed.

The spacewalk is already passed its planned seven-hour duration.

Another spacewalk to continue the job is expected Wednesday.