What was found
DEPARTED SLC, CLIMBING THROUGH 13.5 FOR ABOUT 2 TO 3000 FEET AT 240KT, HAD A LOUD SOUND FROM THE CABIN PRESSURE DOOR THAT EVENTUALLY STOPPED. DESCENDING FROM 8000 FEET TO AT LEAST 6000 FEET @ 2.8PSI, 1300CAB ALT WE HAD ANOTHER LOUD PRESSURE SOUND FROM THE DOOR. CORRECTIVE ACTION: REPLACED EMER SHUT OFF VALVE. OPS CHECK GOOD. IAW CESSNA 680A MM 21-12-05