What was found
FLT CREW & FA1 SMELLED WHAT SEEMED TO BE A BURNING SMELL. SUSPECT SMELL CONSIDERED ASSOCIATED WITH NR 2 PACK FAILURE. DEFERRED NR 2 PACK. RAM AIR INLET DOOR CONFIRMED OPEN. DURING TAXI IN FOR A/C OVERNIGHT MX AND OPC OF RT PACK WITH AMM 21-51-00, PACK2 FAIL CAUTION MSG POSTED ON EICAS. FAULT CODE 21516700AM1 AND FIM TASK 21-51-00-810-802-A. POSSIBLE INGESTION OF SUBSTANCE INTO RT ACM. OPERATED PACK 2 PER AMM 21-51-00, FAULT CODE 21516700AM2 DISPLAYED AND PACK 2 FAIL ON EICAS AND STRONG BURN ODOR ON THE COCKPIT. INSPECTED PACK 2 ACM AND DUAL HEAT EXCHANGERS PER AMM 21-51-05 AND AMM 21-51-04, FOUND RESIDUES OF COFFEE. RECOMMEND TO PERFORM CLEANING OF HEAT EXCHANGERS PER AMM 21-51-04. NO FURTHER DEFECTS NOTED. REMOVED AND REPLACED RT ACM IAW MM CH 25-51-05. OPC GOOD.