Date: 201708
Local time of day: 0601-1200
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Light: Daylight
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
ATC / advisory: Center ZZZZ
Aircraft component: Aircraft Cooling System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Relief Pilot
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We arrived at the aircraft to discover a deferral sticker on the equipment cooling panel. There was no deferral number on the sticker. There was no deferral for that system on the maintenance release document. We then discovered a status message (FWD GND EXH VAL). We wrote it up via ACARS and contacted local maintenance. Local maintenance came to the cockpit and told us this was deferrable. We pointed out the deferral sticker with no deferral number on it. The mechanic removed that sticker. A new sticker was placed in the same location with the proper deferral number on it. Based on the deferral; a review of the maintenance release document and what the mechanic told us; we felt we had the proper indications for the degraded system. We departed ZZZZ on Runway XX via [a departure procedure]. This is an involved noise abatement departure requiring the attention of all three pilots. Once we were established outbound; I noticed my ears popping. More so than usual. I looked up at the pressurization panel and noticed the cabin was climbing at the same rate as the airplane. We were approaching FL100. We requested to maintain FL100. We ran the FWD EQPT VAL checklist. The valve light remained illuminated after the checklist was completed. The aircraft started pressurizing. We knew the issue was not resolved but we wanted to get to a safer altitude (away from VFR traffic and terrain) and a more fuel efficient altitude. We climbed to FL120. The aircraft was still pressurizing. We requested a higher altitude. At approximately FL190 the aircraft lost pressurization. We performed the immediate actions for a rapid depressurization. We [advised ATC] and descended to FL 100. During the descent the cabin altitude warning horn activated. The cabin oxygen masks did not deploy. We asked for a present position hold to work the issue and contact the company. The copilot was the flying pilot. I asked the International Reserve Officer (IRO) to takeover ATC communications. With the aircraft at a safe altitude and location; I attempted to establish communication with dispatch. I was unable to contact company with SATCOM. We kept getting disconnected. I switched to HF and contacted [commercial radio] and requested a phone patch to dispatch. I was able to talk to dispatch and Maintenance Control via HF. Maintenance Control said the issue could not be resolved in flight. Dispatch and I assume the Duty Manager; requested that we return to ZZZZ. I told dispatch we would dump fuel and burn off excess fuel so we could make a below max weight landing. We got clearance from ATC to dump fuel. We ran the appropriate checklist and dumped 35;000 LBS of fuel from the center tank. We still needed to burn off 30;000 LBS of fuel. We configured the aircraft for maximum fuel burn. APU on; gear down and flaps down. At some point while holding; we got an OVHT light on the equipment cooling panel. We ran the appropriate checklist and selected OVRD. This caused the equipment cooling light to illuminate. We ran the appropriate checklist for that issue. That checklist suggests we could lose avionics in 90 minutes. We made the decision to abandon the idea of making a below max weight landing. We requested clearance to ZZZZ. We cleaned up and accelerated. I went back to standby on the equipment cooling panel. The overheat light extinguished and remained off. We speculated that going back to standby and speeding up gave us our cooling back. With the airport in sight and only 10 miles away; we made the decision to do the final turns in [a hold] to burn off the required fuel to make a below max weight landing. We requested ILS approach. This is the longest runway at ZZZZ. We made a normal landing that was below maximum landing weight. We returned to the gate. All of the training we receive has paid off. I delegated authority and assigned duties to prevent myself from being overloaded. We seemed to solve one problem to only find another. What happened in the cockpit is exactly what happens in the simulator. It felt like this emergency was a non-event.


Second narrative: [Report narrative contained no additional information.]


Synopsis: B767 flight crew reported being dispatched with FWD GND EXH VAL on MEL. During climbout the aircraft did not pressurize and the flight returned to the departure airport.