What was found
(CAN) AFTER DEPARTING, THE CREW OBSERVED AN INDICATION OF ANTI-ICE SELECT FAILURE ON NR1 ENGINE. THE CREW RETURNED TO DEPARTURE, WHERE MAINTENANCE FOUND INTERNAL PARTS FROM THE THERMOSTATIC VALVE FOR THE NR1 LT NOSE COWL ANTI-ICE HAD FOULED THE ANTI-ICE VALVE. THE CONTAMINATION WAS REMOVED, THE THERMOSTATIC VALVE, AND THE ANTI-ICE VALVE WERE REPLACED BEFORE THE AIRCRAFT WAS RELEASED FOR RETURN TO SERVICE.