B767-300 and 300 ER
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
After engine start and bleed configuration; a faint 'dirty socks' smell was detected. The odor only lasted a few minutes then dissipated. During takeoff; the odor returned and was far more intense. The odor remained through approximately FL250. No visible fumes were observed but the odor was strong enough to be distracting; although it was difficult to determine if any physical effects were present. After passing FL250; the odor was no longer present. After landing; the left engine was secured; and the odor returned temporarily. A maintenance log entry was made of the event; and that aerosolized oil was suspected to be entering the bleed system; and MX personnel stated an inspection would be conducted. We were to have a 3.5 hour sit; then fly the same aircraft; but the inspection forced a tail swap.  I happen to speak with a crew member who flew the aircraft after the maintenance inspection; which was unable to be duplicated the odor. After the flight; that crew member also detected the 'dirty sock' smell but did not notate the event because they were under the assumption the smell was due to a 'dirty air filter.' Unfortunately; most pilot are unaware; due to lack of company training/notification; that this condition is toxic to the aircraft occupants and should be addressed. Much documentation has been made of the engine oil additive TCP: (TCP; used as additives to all aviation engine oils to reduce wear; are not intended for consumption; acute symptoms include stomach cramping; muscle aches and sinus congestion which may be mistaken for flu or food poisoning and can lead to delayed onset of OPICN (Organophosphate Induced Chronic Neurotoxicity)'); which produces this odor; but a lack of industry training is problematic.
B767-300ER Captain reported a 'dirty socks' odor after engine start which dissipated and returned after landing.