Date: 201812
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: B787-900
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
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); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Time Pressure; Communication Breakdown; Human-Machine Interface
Second reporter function: First Officer
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew; Person Maintenance
When detected: Pre-flight
Contributing factors: Company Policy; Human Factors; Procedure; Staffing
Primary problem: Company Policy

Narrative: When the Relief Pilot was doing the walk around he was initially told by a Mechanic located in the wheel well that we had an issue with the left Liquid Cooling system. When Maintenance was bringing the airplane from the hangar to the terminal; they noticed the system was down to .69 with a RF indication. When Maintenance came back up to the flight deck; he said the minimum to go was .41. The airplane spent the night at the hangar; but the system apparently wasn't checked or serviced. The maintenance log was signed off. A little later we thought with it down to .55; maybe we did in fact have a leak. So; we decided to call Maintenance back out. They indicated it might be awhile; so I called [Maintenance Control]. I mentioned that we appeared to be losing fluid and I was not sure all was good to go. He told me the minimum was higher than .41 (turns out .41 appeared to be correct) and that he didn't think we were good to go and that they suspected a leak due to a history of decreasing quantity. They felt it should be checked first. I was told they thought of taking the plane out of service; but was told that they felt pressure from above not to take it out of service. It was [Maintenance Control's] opinion that it should not go as is. At that time another Mechanic showed up in the cockpit. He in turn called [Maintenance Control] as well; came back and said it was not good and that the airplane probably shouldn't go. I had 2 different people basically tell me it shouldn't go; but I had to make the decision as to whether or not to take it. At that point; I had my suspicions and with the information I had at the time; I decided I was not going to take the plane. It was tough; because we were all boarded and ready to go. It was a decision I absolutely did not want to have to make. Well; as you can imagine; supervisors started showing up. A Maintenance Supervisor got involved with [Maintenance Control] and from what he told me; there was a heated discussion between a few technicians as to what the actual situation was. Anyway; at some point the original Mechanic that initially signed off the logbook returned. He told me in no uncertain terms that there was not a leak and that the drop in fluid was due to them working on the system and not a further leak. So; after being told that we were in fact above the minimum fluid and were assured we did not have a leak; I in consult with my cockpit crew; reversed my original decision and accepted the aircraft. We ended up leaving 48 minutes late.That unfortunately is not all. It gets more interesting. Upon arriving in [our destination]; I pulled up the [maintenance follow up] and saw where there was an entry on the same day by [Maintenance Control] indicating that they suspected a leak in the system due to the fluid level dropping quickly every few days and that a leak check and repair should be completed. When I checked the next morning; the entry was no longer there. After the aircraft flew back; the return crew wrote up the issue again. The maintenance log then showed that they found the left hand PECS (Power Electronic Cooling System) pump filter housing leaking and the check valve in the pump was also leaking. This was then repaired. I feel this is a serious case of plane pushing. We are concerned about delays (as we should be); yet the airplane sits at the hangar the entire evening and night before an ETOPS (Extended Twin Operations) flight and these systems and fluids are not checked until the last minute especially knowing they suspected something was amiss with a history of dropping cooling system quantity and a potential leak. Then; there appears to be a problem and I am told by Maintenance that the airplane should not go; that it should be taken out of service but there is pressure not to. Then I am told that actually there is no leak and that all is good. We take the plane only to find out it did in fact have a leak and was taken out of service after its return to havethe leak repaired. They found the left hand PECS pump filter housing and the check valve in the pump leaking. I sincerely hope I am wrong in my suspicion of plane pushing and that there is no pressure on Maintenance to push aircraft; especially on an ETOPS flight. I must say that my crew and I found this situation very suspicious.I think there needs to be better and more accurate communication with Maintenance so that the flight crew can make the most accurate decisions as possible. I also believe that there might be pressure from the top to push aircraft; leaving decisions that should be made by Maintenance on the Captain.


Second narrative: During the pre-flight the Relief Pilot noticed Maintenance was doing some work in the wheel well. When he came back to the cockpit; he noticed the Liquid Cooling quantity had an 'RF' message on the right unit. He notified the Captain and Maintenance was called for clarification. Initially Maintenance said there was a leak but later said there was no leak. They did not have the equipment at the ramp location to refill the cooling system. They said the plane would have to go back to the hangar (where it had just been while on an overnight service) to be refilled. They then came back and said that we were good to go with the indicated quantity (.56) because the minimum was .41. This caused a lot of discussion between the crew and maintenance. We were told by the Mechanic that his license was on the line and that the airplane was safe to fly.After the [round trip flight]; the inbound crew wrote up the discrepancy again. Now Maintenance did an inspection and apparently they did find a leak in the system. I asked the Maintenance Technician why we would leave a major maintenance base with a 'RF' indication; especially before an ETOPS flight; and again he said its my license on the line and you are good to go.There is no guidance in our operating manual about the Liquid Cooling quantity levels. It does state in the preflight checklist that there should be no 'RF' on the hydraulic gauges but nothing for the cooling system. We tried to argue that if [the manufacturer] thought it was important enough to place a 'RF' indication on the hydraulic system; then the same logic should hold for the cooling system. Maintenance wanted no part of that discussion.


Synopsis: B787 flight crew reported a low quantity indication in the liquid cooling system caused a delayed flight; only to reappear the next flight when a leak was discovered.