B737 Undifferentiated or Other Model
Flight Crew Last 90 Days 187; Flight Crew Type 11000
Training / Qualification
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action; General Release Refused / Aircraft Not Accepted
Aircraft; Human Factors
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.
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.