What was found
BLEED 2 FAIL EICAS MESSAGE, PACK 2 FAIL EICAS MESSAGE AFTER TAKEOFF. RAN QRH, PACK 2 FAIL 5 MINUTES LATER. DECLARED EMERGENCY, RETURNED TO FIELD, LANDED WITH NO FURTHER INCIDENT. R&R RT TMC IAW AMM 170 36-11-06, OPS AND LEAK CHECK GOOD. COUND NOT DUPLICATE PACK 2 FAULTS, OPS CHECK GOOD.