B737 captain reported he was not satisfied with maintenance releasing his aircraft for service after...

Narrative:

The aircraft was towed to gate and parking brake set. A few minutes later the aircraft dumped approximately a gallon of hydraulic fluid onto the ramp. Maintenance control was called and contract maintenance was called out. After discussing in some length with contract maintenance and maintenance control; they came to a conclusion that it was the system 'venting.' I have flown here for [many] years and never seen this. They insisted this was a normal thing and that there wasn't a leak. I finally asked for them to describe where the 'venting' comes from in the wheel well and to describe the place while I was in the wheel well on my phone. So they started to describe a place low near the belly below the B system reservoir. After they finished describing; I told them that is not where it was coming from and told them about a pressure gauge where all the fluid was dripping from. I even got the maintenance control's cell number and took pictures and texted them to him. After 20 minutes; the contract maintenance guy changed his tune and said he was not letting the aircraft fly because of the leak. The aircraft was pulled from service. So in summary; the aircraft was 'good to go' but ended up being pulled from service after I stood my ground. My concern is what happens when this same attitude is presented to a captain who takes maintenance by their word and flies the aircraft.

Original NASA ASRS Text

Title: B737 Captain reported he was not satisfied with maintenance releasing his aircraft for service after a hydraulic leak was found. Maintenance ultimately agreed with the reporter.

Narrative: The aircraft was towed to gate and parking brake set. A few minutes later the aircraft dumped approximately a gallon of hydraulic fluid onto the ramp. Maintenance Control was called and Contract Maintenance was called out. After discussing in some length with Contract Maintenance and Maintenance Control; they came to a conclusion that it was the system 'venting.' I have flown here for [many] years and never seen this. They insisted this was a normal thing and that there wasn't a leak. I finally asked for them to describe where the 'venting' comes from in the wheel well and to describe the place while I was in the wheel well on my phone. So they started to describe a place low near the belly below the B system reservoir. After they finished describing; I told them that is not where it was coming from and told them about a pressure gauge where all the fluid was dripping from. I even got the Maintenance Control's cell number and took pictures and texted them to him. After 20 minutes; the Contract Maintenance guy changed his tune and said he was not letting the aircraft fly because of the leak. The aircraft was pulled from service. So in summary; the aircraft was 'good to go' but ended up being pulled from service after I stood my ground. My concern is what happens when this same attitude is presented to a Captain who takes Maintenance by their word and flies the aircraft.

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.

Attributes
ACN	1276221
Time
Date	201507
Local Time Of Day	1801-2400
Place
Locale Reference	ELP.Airport
State Reference	TX
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Flight Phase	Parked
Component
Aircraft Component	Hydraulic System
Person 1
Function	Captain
Experience	Flight Crew Last 90 Days 187 Flight Crew Type 11000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Maintenance Deviation - Procedural Published Material / Policy

B737 captain reported he was not satisfied with maintenance releasing his aircraft for service after a hydraulic leak was found. Maintenance ultimately agreed with the reporter.