Impossible to know where the leak was originating from as mechanics were not able to spot the origin themselves (amazing I find !...)
If only it was always that easy!
Not 737 related but just to give you some idea that it's not always that straight forward.
I recently had an a/c arrive on stand, shut down, did the normal checks and we had to put a lot more than normal uplift of oil into an IDG/CSD, there was also a write up in the log about IDG/CSD oil temp etc, gets hot when there isn't a lot left in there.
Now a visible check didn't reveal any obvious leaks. OK, not a problem, ran the engine up still no leaks, strange, still have seen it before when a previous base has not topped up or checked the oil levels. Then after about 10 mins after shutting down the engine, a large puddle of oil appeared under the said engine. Very strange, had a look still couldn't see any leaks, topped it up and when through the same scenario. Lo and behold after 10 mins oil coming out again. Found where the leak was and sorted it, it was actually coming from a joint on the generator. So what was happening? Once the engine was run up and the oil in the CSD/IDG became pressurised there was no leak at all, once the pressure dissipated then the leak became apparent.
I've also seen similar things with hydraulic leaks, a/c arrives there's been a drop in oil qty, you can find the area that is soaked in hydraulic fluid, can you find the leak when pressurising the system, can you heck. But once the pressure is dissippated and the hydraulic lines relax it becomes apparent that it is a low pressure leak from a quick release coupling that seals itself when pressurised because the line straigtens itself and seals better than when unpressurised it sags down slightly opening the joint.
So the moral is although it seems quite obvious that there is a leak it's not always so obvious where it originates.
I would say that any maintenance organisation that is worth it's salt will be on top of it and monitoring the uplifts and once it reaches the stage where the consumption limit is reached the a/c would then be taken out of service. Not that there is any commercial consideration or pressure involve........ha!
