Narrative:

We called maintenance while at the gate due to a burning smell around the forward entry area. The mechanic checked out the area and signed off the logbook as unable to duplicate; as the fumes went away when the packs were cycled off and on. On taxi out; the purser called to say the fumes were back. Since maintenance had just checked out the airplane; we agreed that; since the gate was in a congested area; up in the alley where odors from lots of vehicles could be picked up; and since there were about a dozen aircraft ahead of us for takeoff; that we would sit out in the open; waiting for takeoff; and give the fumes a few minutes to dissipate. I called the purser shortly before takeoff; she checked with all the flight attendant stations; and they were unanimous in that the fumes were gone. Going through 3;500 feet on climb out a flight attendant; not the purser; called and said; 'captain! You need to turn around and go back right now! The fumes are horrible back here.' shortly after that; about 5 or 6 thousand feet; the purser called to say the fumes were back and real bad. I asked the first officer to go back and assess the situation in the cabin. The first officer returned to say that he could smell a very faint odor; but based on the situation in the cabin; he would recommend returning to [departure airport ZZZZ]. [Requested priority handling with ATC]; landed overweight; auto brakes off and I rolled down the length of the runway to save the brakes. Landed at 518;000 pounds. Twice enroute to ZZZZ I checked with the purser and both times she said the odor was dissipating. The first officer ran the emergency landing checklist and the ACARS diversion report.ZZZZ operations said that the culprit was a bearing in a cooling fan.

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Original NASA ASRS Text

Title: B777-200 Captain reported that during the climb fumes in the cabin were so extreme they had to return to the departure airport.

Narrative: We called maintenance while at the gate due to a burning smell around the forward entry area. The mechanic checked out the area and signed off the logbook as unable to duplicate; as the fumes went away when the packs were cycled off and on. On taxi out; the purser called to say the fumes were back. Since maintenance had just checked out the airplane; we agreed that; since the gate was in a congested area; up in the alley where odors from lots of vehicles could be picked up; and since there were about a dozen aircraft ahead of us for takeoff; that we would sit out in the open; waiting for takeoff; and give the fumes a few minutes to dissipate. I called the purser shortly before takeoff; she checked with all the flight attendant stations; and they were unanimous in that the fumes were gone. Going through 3;500 feet on climb out a flight attendant; not the purser; called and said; 'Captain! You need to turn around and go back right now! The fumes are horrible back here.' Shortly after that; about 5 or 6 thousand feet; the purser called to say the fumes were back and real bad. I asked the First Officer to go back and assess the situation in the cabin. The First Officer returned to say that he could smell a very faint odor; but based on the situation in the cabin; he would recommend returning to [departure airport ZZZZ]. [Requested priority handling with ATC]; landed overweight; auto brakes off and I rolled down the length of the runway to save the brakes. Landed at 518;000 pounds. Twice enroute to ZZZZ I checked with the purser and both times she said the odor was dissipating. The First Officer ran the emergency landing checklist and the ACARS diversion report.ZZZZ operations said that the culprit was a bearing in a cooling fan.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.