A320
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Physiological - Other
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
Shortly after the First Officer and I boarded the aircraft in ZZZZ the inflight crew said they smelled the dirty socks smell coming out of the air conditioning system.  I agreed with their assessment and we coordinated contract maintenance via phone with Maintenance Control.  After lengthy troubleshooting (including low power engine run) the fumes were isolated to Pack #2.  There was also a bit of residual fumes using Pack #1 on APU bleed air (however no fumes were noted using Pack #1 on engine bleed air).  Maintenance eventually decided to defer Pack #2 and dispatch our flight.  Oil servicing of the APU system was also checked; however no issues were noted.  The #2 Inflight crewmember reported to me that she had a headache that she determined was caused by the fumes.  We eventually departed 5 hours late for the flight to ZZZ1.
A320 Captain reported a fumes event during pre-flight. After a lengthy maintenance delay; Pack #2 was deferred and the flight departure.