As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: PASSING 6000 IN THE DESCENT FOR THE ARRIVAL INTO IND, FLIGHT CREW EXPERIENCED A DIRTY SOCK SMELL AND IMMEDIATELY TURNED OFF PACK 1 TO ALLEVIATE THE SMELL. FUMES CONTINUED FOR ABOUT 4 MINUTES AND THEN SLOWLY DISSIPATED. MAINTENANCE FOUND STREAKING FROM THE AIRCRAFT BELLY INTO THE APU INLET. MAINTENANCE FOUND THE YELLOW HYDRAULIC SYSTEM RESERVOIR DRAIN VALVE LEAKING AND REPLACED IT PER AMM 29-13-41.