Date: 201707
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Hydraulic Fluid
Reporter organization: Air Carrier
Reporter function: Captain
Human factors: Troubleshooting; Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Maintenance Action
Contributing factors: Aircraft; Company Policy
Primary problem: Aircraft

Narrative: During preflight; I discovered that the A hydraulic system was serviced to 106%. I sent in a report and contacted maintenance on the radio. Two mechanics showed up and performed a maintenance procedure which uses a combination of cycling the hydraulic pumps and the parking brake to transfer fluid from the A system reservoir to the B System Reservoir. Unfortunately; there was not quite enough room in the B Reservoir and when the transfer was completed; both systems showed 101% on the cockpit engine display. I requested to the mechanics that they service both systems to have them show 100% or lower on the cockpit display and was told that 101% was satisfactory and they would not perform further service. I explained that I would refuse the aircraft if necessary. They stated that they didn't care what I did that they weren't going to service the aircraft.Per the [Flight Manual]; I called dispatch from the podium phone and was conferenced with [Maintenance]. I explained the issue and [Maintenance] stated that he would have maintenance service the aircraft.When I returned to the cockpit; I had received an ACARS message to call maintenance on the radio. When I called them; the person who answered challenged my knowledge of the 737 Flight Manual. I told them that as the Captain; I was requesting this service. He made a snarky remark about Captains trumping the flight manual to which I answered that that was obnoxious and we needed to get this done so we could get the passengers to [our destination]. I terminated this conversation before it became more heated.A supervisor then came to the cockpit and identified himself as 'the Lead.' He stated that they were not going to service the aircraft and showed me language from the Boeing Maintenance Manual that stated; 'When full; the gauges will show 100% +/- 9%.' I explained that this wasn't relevant as it only gives gauge tolerances for full reservoirs and that there was further language in the same section that stated (in capital boldface font per the manual):'CAUTION: BEFORE RETURNING THE AIRCRAFT TO SERVICE; ENSURE THAT THE QUANTITY GUAGES DO NOT READ ABOVE 100%. THE HYDRAULIC FLUID QUANTITY GUAGES ARE CAPABLE OF READING UP TO 106%. IF THE GUAGES READ ABOVE 100%; HYDRAULIC FLUID COULD LEAK INTO THE PNEUMATIC SYSTEM CAUSING EQUIPMENT DAMAGE AND POSSIBLE INJURY TO PERSONS. IF THE GUAGES READ ABOVE 100%; DRAIN HYDRAULIC SYSTEM FLUID FROM THE RESERVOIR UNTIL THE TRANSMITTER AND ENGINE DISPLAY INDICATOR READ TWO-THIRDS BETWEEN REFILL (RFL-76%) AND FULL (F-100%).'The lead then stated that the aircraft was airworthy and he was going to sign it off as such. I reiterated that I wanted both systems serviced to 100% or lower and he stated that this wasn't going to happen.Again; I went to the podium and called dispatch and [Maintenance]. I explained that despite the refusal; new maintenance would not service the aircraft. [Dispatch] again stated that he would get them to do it.During this time; I received a call on my cellphone from a retired pilot in the ramp tower. He wanted to know what was going on and I explained it to him. He asked me to properly refuse the aircraft with dispatch and I told him that I had over 15 minutes ago. Sometime later; at least 2 mechanics showed up and started to work the problem. They were quite angry and agitated and made comments like; 'that's the guy' (while pointing at me) and 'why are you making us do this...'The servicing; which normally takes 10-20 minutes took well over an hour. The whole time; the passengers were sitting on the hot aircraft (it was 90+ degrees outside) and I coordinated with the flight attendants to have water served and made announcements. At one point; we assessed whether or not to de-plane but decided that the airplane was nearly ready to go and didn't want to further delay the flight.I spent most of this time on the jetbridge with the First Officer; a cockpit jumpseater; and a few gate agents. They witnessed; most if not all of the event; and were appalled by the reaction and open hostility from the maintenance staff.Once the service was completed; we got the aircraft ready and departed. On a side note; there was weather that moved into the area that caused a 1 hour delay on the taxiway. We would have beaten this weather and gotten out if the aircraft had been properly serviced without a major fight. Also; this unnecessary delay caused us to run out of duty time [at our destination airport] and further inconvenience other passengers.During this ordeal; I was inundated with hostility from mechanics and supervisors. It was not helpful to be antagonized and pressured over the radio by the maintenance controller. The retired pilot seemed interested in what was going on but at no time offered any assistance to solve the problem. His involvement was just another nuisance and unnecessary distraction.The bottom line is that the 737's have a problem of over-serviced hydraulics. It is noted as a caution note; in capital and bold font per the Boeing maintenance manual that this is an unsafe condition which can result in 'personal injury.' Recently; [another airline] pilot was exposed to toxic fumes and experienced sever neurological damage and ultimately passed away as the direct result of poisoning from pyrohydrolized oil (super-heated oil in the air-conditioning and bleed ducts). I had a similar event that didn't result in any known long-term injury that was the direct result of an over-serviced hydraulic system.I have never experienced such a hostile environment and pilot pushing as I did by maintenance. No pilot should have to be exposed to such behavior while trying to uphold safety and maintain the operation.




Synopsis: Boeing 737 Captain reported receiving hostility and challenge from Maintenance and Supervisors when writing up an over serviced hydraulic system.